Fire management plan ODMP Draft Report First Section June 2006

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Okavango Delta Management Plan – June 2006

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of the environment in the Moremi Game Reserve and similar to the other forms of land use in the Ramsar Site requires consideration in the formulation of the fire management plan.



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improves the quality of papyrus (Cyperus papyrus) that is harvested for making household mats. Thus these activities are another ignition source for fires in the Ramsar Site. 4.5.2 Wildlife management areas 4.5.2.1 Tourism The growth in value and benefits from tourism have been enormous and income from tourism is the second highest income generator after diamonds in Botswana. The Okavango Delta conjures up two images for many people – one a vast area of swamps and the other an abundance of wildlife. These two features form the basis for the tourism industry in the Okavango Delta Ramsar Site that involves both community and commercial photographic concession areas where tourists visit and are accommodated in lodges and tented camps in designated areas to view and photograph wildlife and the scenic beauty of the Okavango Delta. The other form of tourism is community and commercial based wildlife utilization in the wildlife management areas and in the controlled hunting areas. This involves commercial trophy hunting of large African ungulates under strict government regulations administered by the Department of Wildlife and National Parks. Sixty percent of people employed in Ngamiland are employed either in the tourism industry or in the services and infrastructure that support the industry and therefore this form of land use is of enormous social benefit to the communities living in the Ramsar Site. The aforementioned tourist activities are located in extensive tracts of Permanent Swamps, Seasonal Swamps and the different woodland communities and intentional and unintentional fires are a frequent and often controversial feature of the different forms of land use in these areas. Therefore the effects and use of fire in these tourist related areas requires serious consideration in the formulation of the fire management plan for the Okavango Delta Ramsar Site. 4.5.3 Game reserves The land use category “game reserves” in Table 5 refers to the Moremi Game Reserve located in the Okavango Delta Ramsar Site. It is regarded as one of the premier wildlife destinations in Africa and covers approximately one third of the Okavango Delta. It is surrounded by the wildlife management area dealt with in section 4.5.2 and because it is not fenced it allows free movement of wildlife across its borders providing a safety zone during the hunting season (Roodt, 2006). Moremi forms an important component of the tourism industry in the Ramsar Site and contributes significantly to the economic viability of the area. A major portion of the Reserve comprises Mopane Woodlands with magnificent forest stands of tall cathedral mopane trees. Besides mopane it has a great diversity of the different vegetation units and includes extensive channels of Permanent Swamp, large areas of floodplains in the Seasonal Swamps at Khwai and Xakanaxa (Roodt, 2006) and Acacia Woodlands on Chiefs Island. The Moremi Game Reserve is administered by the Department of Wildlife and National Parks in Maun. In discussions with departmental officials it was stated that no controlled burning is applied as a management practice in Moremi and in accordance with it being a natural area, lightning is recognized as the only natural source of ignition permitted in the area and all anthropogenic fires entering or occurring in the Reserve are controlled as far as possible. Fire is therefore a natural factor



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much easier than elsewhere where most settlements are further from the fishing grounds. Fish populations are most concentrated in September to December when the Okavango River is at its lowest and these are the peak months for fishing. In the Delta 46% of people fish with line and hooks, 42% with baskets, 14% with gill nets, 9% with spears and 6% with traps. (Mosepele, 2002). Of the various habitats, the floodplains in the seasonal swamps are of the greatest value as places in which most fish breed. The most important feature of the flooded areas is that they are rich in nutrients, which, together with the water, allow a lush growth of plants and the emergence of insects and other small animals. All these organisms provide young fish with a plentiful supply of food (Mendelsohn & el Obeid, 2004). The flood plains are very important breeding grounds for native tilapia fish (mainly Oreochromis and Tilapai spp.) which is partly due to the slower flow of water, greater cover, and decreased vulnerability to predation by tiger fish (Hydrocynus vittatus) (Cassidy, 2003). The significance of fishing in the Okavango Delta to the fire ecology of the Ramsar site is that fisherman are an important source of ignition using fire to remove excessive plant growth to facilitate the setting of their nets in the water channels and lagoons. Fire is also used to maintain the channels in an open condition to facilitate movement in their mokoros associated with fishing activities (Cassidy, 2003). 4.5.1.4 Hunting There is little information available on the extent of subsistence hunting as this topic is a sensitive issue and understandably rural communities are not willing to divulge information. Since there appears to be a correlation between burning and hunting, as many stakeholders attribute wildfires to hunters and/or poachers rural communities fear prosecution under the Herbage Preservation Act. Tinley (1975) however, mentions that the Masarwa River Bushmen in the then Moremi Wildlife Reserve lived by hunting and were responsible for burning the flood plain grassland, which sometimes burnt for weeks. Cassidy (2003) reported that in interviews with communities it was stated that local hunters like burning to attract game but that it had decreased in recent years because of more effective law enforcement. Therefore hunting by rural communities is also a source of ignition for fires in the Okavango Delta Ramsar Site. 4.5.1.5 Harvesting reeds, thatching grass and papyrus Reeds harvested from communities of Phragmites australis and P. mauritianus in the Permanent and Seasonal Swamps are an important source of building materials for rural communities in the Ramsar Site. Most of it is used for domestic purposes and for the immediate benefit of households, but plant products are also sold to earn cash incomes, and many goods are exported from the region. Most houses are thatched with grass and/or reeds, while reeds are used extensively to make sleeping mats, walls, palisades and fences (Mendelsohn & el Obeid, 2004). Several grass species like Aristida stipitata, Cymbopogon excavatus, Eragrostis pallens, Hyparrhenia rufa and Miscanthus junceus are harvested by rural communities for thatching material for domestic purposes but also increasingly for sale to commercial tourist operations. Cassidy (2003) reported that in interviews with rural communities areas used for gathering thatching material and reeds are not harvested annually and in the intervening year are often burnt to improve the quality and quantity of the material produced by these plant communities. It was also reported that burning also



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households have no livestock (48% of farmers have no cattle and 61% have no goats). Cattle and goats are more abundant than sheep pigs and donkeys and before the provision of water from boreholes most of the livestock were concentrated close to the Okavango Delta. However, there are now there are large herds to the south west of the Delta that are kept in cattle posts in open communal or tribal areas, or on large fenced farms allocated to individual farmers. Numbers of cattle have slowly increased in Ngamiland since the drastic measures taken in 1996 to control contagious bovine plural pneumonia (CBPP). Livestock bring a range of benefits to their owners: draught power is provided by oxen and donkeys, milk, leather, meat and most importantly security and investment opportunities (Mendelsohn & el Obeid, 2004). Overstocking, however has led to the loss of pastures in the drier areas of the Ramsar Site hence substantial numbers of cattle are grazed on the floodplains in the Seasonal Swamps when the annual flood subsides. Wildlife grazing also coincides with that for cattle. The main livestock rearing areas in Ngamiland are Maun/Shorobe, Toteng/Sehithwa/Tsau, Nokaneng/Gumare, Shakawe, and Seronga. The areas from Nokaneng southwards to Lake Ngami and eastward to Toteng are primarily used as grazing land intermixed with small arable fields (Bendsen, 2003). 4.5.1.2 Crop farming Of the 48 900 hectares cleared for cultivation in Ngamiland only approximately 10 000 hectares are cultivated annually, of which 75 % is dryland cropping and 25% molapo or flood recession farming. Along the Panhandle and in the Etsha area, where the HaMbukushu are the dominant ethnic group, dryland farming is the main land use activity. Molapo cultivation is found in the floodplains at the western and south eastern fringes of the Okavango Delta, mainly in Tubu and in the Shorobe-Matlapaneng area (Bendsen, 2003). There are 8 500 farming households close to the Okavango Delta in Ngamiland. Each household normally cultivates a few hectares and sometimes keeps small herds of cattle and goats, 95% or more of all farming is practiced on this basis. Farmers generally cultivate pearl millet, maize and sorghum with watermelons, pumpkins and other crops being grown to a lesser extent. True subsistence farming is only practiced by the poorest households, who live mainly on the food they harvest with some additional food coming from fish, honey and wild fruits. Crop farming is a summer activity and it is critical to prepare fields early so that crops can be planted in December in order to take advantage of the heavy rains in January and February. Careful timing of crop growth is more critical on dry-land fields than with molapo farming where the ground remains moist for much longer. Molapo fields are planted, mostly to maize, as the flood waters begin dropping, normally in September and October. New fields are cleared for agriculture using the slash-and-burn method but the growing number of people has limited the areas in which new fields can be cleared so rural households have to use the same fields repeatedly. Since fertilizers, manure or compost is not used to replenish soil nutrients fertility has declined. The farmers usually burn their fields to clear them and in an effort to increase soil fertility (Mendelsohn & el Obeid, 2004). 4.5.1.3 Fishing Approximately 3 200 people are involved in fishing in the Okavango Delta, the majority of which are small-scale fishermen who catch food for domestic consumption. The highest concentration of fishermen is in the Panhandle because access to permanent water is



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farmers from about 1 500 years ago. Livelihoods during the long history of the Delta were based on hunting, fishing and gathering, and most researchers agree that people living during the more recent Late Stone Age would have been so-called Khoesan people. Some Khoesan remained as hunter-gatherers and the ancestors of modern San people, but others switched to livestock farming. Farming could have started here as long as 2 000 years ago after Bantu farmers arrived in southern Africa from east and west Africa (Mendelsohn & el Obeid, 2004). Tinley reports that according to Stigand (1923) the Bayeyi first arrived at Lake Ngami in about 1750, from north on the Linyanti, and another group of the same people migrated southwards to the lower reaches of the Okavango River. The only inhabitants they found were Masarwa River Bushmen in the swamps, the Bushmen lived in the sandveld, and the Makalahari who lived in the Kwebe Hills. The Bayeyi cultivate to some extent, but live mostly by hunting and fishing, using both portable and fixed nets and vegetable poison. In about 1800 the Batawana moved north and settled first near Lake Ngami and the Kwebe Hills. They subsequently moved on a number of different occasions to different parts of the Okavango Swamp margins, and today are settled mainly at Maun. Stigand noted that in 1923 Maun was composed of 500 dwellings. The Batawana hunted and kept large herds of cattle. Tinley also reported that in Gibbons in 1899 recorded that along the Makwegana Spillway (Selinda Spillway) the country was densely populated by Mampukushu and their large numbers of stock, and it was extensively cultivated. According to Tinley (1975) Stigand (1923) notes that swamp and reed beds were burnt annually in preparation for ploughing, and that it takes about 5 years for reed swamps with soft soil to be converted to a hard surface covered in short lawn-like grasses. Likewise he quotes Pole-Evans (1948) who after an expedition to Ngamiland in June - July 1937 “is convinced that the lessening of the free water surface of the internal drainage basin has been due to natural plant succession, in which, over time, vegetable remains are slowly deposited, the shores are pushed outward and the area of open water reduced in size; this process of deposition being aided for more than two centuries by man and his stock, fire and shifting cultivation in and around the swamps”. In view of the importance and effects of land use on the biota in the landscape a brief overall description will be presented on the different activities associated with the aforementioned categories of land use presented in Table 5. 4.5.1 Communal areas, settlements, arable and pastoral agriculture 4.5.1.1 Livestock Farming The majority of tribal land in Ngamiland district has been zoned for communal use and according to customary law, all tribesmen have open access to grazing and to natural surface water for stock watering to meet their subsistence needs (Bendsen, 2003). Approximately half of the households in Ngamiland own cattle, goats, sheep, donkeys and pigs and there is a great variation in flock or herd size. Data from the 2005 livestock census in the Ramsar Site showed that there are 193 927 cattle, 98 975 goats, 16 000 sheep, 7 276 horses and 12 179 donkeys (ODMP Draft Framework Plan, 2005). In general, wealthier farmers with large households have the greatest numbers of cattle and goats, while poorer



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4.5 Land Use Besides fire occurring widely in African grassland, savanna and wetland ecosystems it is also frequently an important management practice in the different systems of land use that are applied in these ecosystems. This is also true of the Okavango Delta Ramsar Site and it is therefore necessary to provide an overview of the different systems of land use that are used in the Ramsar Site. This information is provided by the Twanana Land Board Report: Land Use And Land Management Plan, (2006). The current broad systems of land use applied in the Okavango Delta Ramsar Site are presented in Table 5. Table 5. Existing broad land use categories in the Okavango Delta Ramsar Site.

LAND USE CATEGORIES AREA – km2 % Communal areas, settlements, arable and pastoral agriculture

27023 48.8

Game reserves 5205 9.4 Wildlife management areas 23146 41.8

TOTAL 55374 100.0

Note: The total area given in the report is 55 599 km2 which differs from the total area for the Ramsar Site of 55 374 km2 that is officially recognized by the ODMP Secretariat in Maun. Therefore the areas for the different categories of land use have been adjusted accordingly assuming that the proportions for the different categories have remained the same. The data in Table 5 indicates that the communal areas with their associated activities of livestock and crop farming, fishing, harvesting reeds, thatching grass and papyrus, and hunting constitututes the major form of land use in the Ramsar Site with nearly half of the total area involved in this type of land use. The wildlife management areas are slightly less but are involved in the lucrative tourist industry involving both photographic and wildlife utilization activities based both in the commercial and community sectors. Also associated with the wildlife form of land use is the Moremi Game Reserve involved in nature conservation and tourism. All these different forms of land use involve or are affected by fire in a positive or negative manner and must therefore be considered in the formulation of the fire management plan. In doing so it is important to recognize that the area comprising the Okavango Delta Ramsar Site has been settled and used by people for millennia and their livestock, cropping and burning practices having significantly affected the composition, structure and condition of the vegetation. Tinley (1975) states that from an ecological point of view the history of a country is extremely important in fully understanding the ecosystems as they are today. Particularly important are historical factors such as the duration of habitation and specific occupations of the peoples or tribes, and the manner in which the climate-soil inter-relationship has been utilized for subsistence and the marked effect this may have on the appearance of the present day landscape and its vegetation cover. Excavations indicate that the Tsodilo Hills area have been occupied continuously over the past 50 000 – 40 000 years, first by hunter-gatherers and then by livestock and crop



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ecotone between woodland and water. C. dactylon occurring in marginal areas is in many places reduced to an extremely short cover by trampling and grazing but with the first subsurface infiltration of flood waters, or the first rains in November recovers well. Fire burns extremely slowly and usually dies when it enters such lawn grass terrain (Tinley, 1975). The inner part of the floodplain supports grasses that grow up with rising waters, and while remaining rooted in the soil, have emergent parts floating on the surface – especially Acroceras, Echinochloa, Oryza, Panicum and Setaria spp. At the distal end of the floodplain where the inundation is shorter and shallower, grasses such as Cynodon, Paspalum, Setaria and Vetivaria spp. merge into the rainfed grasslands at the edges (Howard, 1992). Trees are rare on floodplains proper in the Seasonal Swamps and are usually found only on levees or islands – these islands sometimes originating from termite mounds that invaded the floodplain during a series of dry years. Palms are characteristic of these areas with Phoenix reclinata on the islands and Hyphaene petersiana on the terraces. The sequence of grasses, sedges and aquatics is often compressed and channels from the main river flood back into the riverine and fringing woodlands giving the appearance of a wooded floodplain (Howard, 1992). In the center of the larger islands, where the ground is salty from trona deposits, only the spiky grass Sporobolus spicatus survives. Figure 14. Hyphaene pertersiana on the terraces in the Seasonal Swamps of the

Okavango Delta.



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Figure 13. The successional plant communities in the channels of the Permanent

Swamps – Vossia cuspidate flanked by Cyperus papyrus with tall Miscanthus junceus in the background.

Depending on the annual flow the boundary between the Permanent and Seasonal Swamps varies yearly. The seasonal swamps are composed of the same complex systems as the permanent swamps, the main difference being the large extent of seasonally inundated areas, usually referred to as delta floodplains (van der Heiden, 1992). Flood waters usually reach the Seasonal Swamps during the dry winter months, although heavy falls of rain may cause local flooding in summer. For any point on a seasonally flooded plain there will be varying degrees of dryness, wetting and inundation caused by the flood, and these may be augmented (and spread out) by local rainfall. This results in changing conditions for flood plain plants and animals and, often, an extended growing season. This extended period of moisture availability and the nutrient recharge from the floods are two conditions that favour the high primary productivity of sub-tropical African floodplains (Howard, 1992). In the Seasonal Swamps the grasslands typically meet the woodlands abruptly in the floodplains. This grassland is seasonally inundated in mid-winter (June – July), to varying depths or the soil becomes moist under foot with no surface water showing. Some margins of depressions and channels are covered by the rhizomatous grass genus Echinochloa (Tinley, 1975) presumably E. stagnina as Field (1976) notes that this species provides valuable grazing for cattle and grows in water in the Okavango Delta and is associated with Vossia cuspidata. Tinley (1975) states this species is usually heavily grazed, and in July aerial portions are rare and the grass canopy has been trampled to a flattened mat. Echinochloa stagnina can occur both in permanent swampy areas of the flood plain and on ground which is only moist seasonally. Cynodon dactylon and Sporobolus spicatus are especially valuable on the margins of the flood plains on the



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are seasonally flooded for months. It also occurs at a few sites along the Nqoga River and according to Smith (1976) this is the most widespread plant community in the Panhandle. The Phragmites mauritianus reedbed community is flooded seasonally to a greater depth and for longer duration than the Pennisetum glaucocladum reedbed community that is situated on elevated scroll bars that are flooded seasonally for short periods (days to weeks) but it also grows in the upper reaches of the Nqoga River. The Miscanthus junceus community is restricted to areas where water levels are relatively constant over annual and decadal time scales (Ellery 2003). Vegetation on the islands in the Perennial Swamps exhibits a marked zonation pattern. Island fringes are often characterized by a broad-leaved evergreen riparian community of Diospiros mespiliformis, Ficus natalensis, F. sycamorus, F. verriculosa, Garcinia livingstonia, Phoenix reclinata, and Syzygium cordatum. This gives way, towards the island interior, to a community dominated by Acacia nigrescens, Croton megalobotrys and Hyphaenea petersiana. The central regions are characterized by either a short, sparse grassland dominated by Sporobolus spicatus or are completely devoid of vegetation, with sodium bicarbonate encrusted soil surrounding a central pan of extremely high conductivity (Cowling et al. 1997). There is a distinct change in vegetation moving outwards from the channel margins to the seasonal flood plains (Ellery et al., 2000). Dense stands of papyrus (Cyperus papyrus) flank the river, while reeds (Phragmites australis) and taller (thatching) grass (Miscanthus junceus) grow on slightly elevated, but flooded land (Cassidy, 2003). A feature of the middle and lower reaches of the Delta is the gradual reduction in size of the Cyperus papyrus plants, decreasing from 3.5 – 4.0 meters in the Upper and Lower Panhandle zones to between 1.5 – 2.0 meters in the Okavango Delta itself (AquaRAP, 2003). Behind the papyrus, the flood plains are mainly covered in shorter aquatic grasses and sedges (Cyperus articulatus, C. denudata, Cladium mariscus and Panicum repens. Small islands have formed in the panhandle where the river channels have moved, leaving perched ridges of sand. These are covered primarily with phoenix palms (Phoenix reclinata) (Cassidy, 2003).



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rhizomes that floats during periods of high flow and subsides during low flows and even during periods of low flows the rhizomes are not aerially exposed. In dominant stands of C. papyrus other plant species make up less that 10% of the standing crop of vegetation (Ellery, 2003). The rapid and abundant growth rate of papyrus is surprising with it occurring in infertile Kalahari sands and in nutrient deficient fresh water, and is as a result of being able to absorb nutrients even when they occur in very low concentrations (Ross, 1987). Papyrus swamps are considered to have the highest primary productivity of any natural plant community, this is because of its ability to recycle carbon and mineral nutrients from old to new portions of the plant (Ellery, 1988). Additional nitrogen essential for plant growth also comes from microscopic bacteria and algae found between the scale-leaves of papyrus and in moist soils but are unable to survive in areas permanently submerged by water. Therefore the dynamics of the flood waters of the Delta during which dry periods occur are critical to the nutrient system of the swamps. The papyrus also has a specialized C4 pathway of photosynthesis absorbing solar energy more efficiently than other plants. Commencing in summer the spiky flower heads of papyrus, called “umbels” produce abundant seeds that fall into the river and are dispersed downstream as they ripen. Seeds that become embedded in the bud germinate but the main form of increase in this species is by vegetative reproduction from its well developed rhizome system. The thick rhizomes that form the papyrus beds send up new shoots at regular intervals and within 90 days have grown, matured and died. This process is continual, and as one shoot dies so the plants withdraws its nutrients and uses them for others. This efficient nutrient cycling is the other reason for this plant species abundant growth which continually accumulates creating a build-up of organic debris causing the water to become acid and deoxygenated (Ross, 1987). Mean height can be used as an indicator of vigour in papyrus plants and a vigorous and expanding community has a greater average culm height and diameter and maintains this height almost to the edge of the community. Circular patches of papyrus with a stunted appearance and domed profile are in a moribund condition and indications are that the frequency of rhizome branching decreases with nutrient availability. There are two growth habits of papyrus: floating and rooted. Floating plants have only delicate, straight, unbranched spongy water roots whereas, rooted plants also have robust, suberised, branched “mud” roots but in all cases the roots of papyrus are adventitious and have no tap roots. When rooted plants are normally submerged, they can be distinguished from floating plants by their shorter rhizome internodes, curved culm bases and low density culms tapering abruptly above the much shorter scale-leaf sheaths. The lightness of the culms is due to the better developed aerenchyma (loosely packed cells with large air spaces, which permit diffusion of oxygen to the rhizomes). The growth rate of papyrus is very high and in Uganda was estimated at 110 tons per hectare per annum (Thompson, 1974) and according to Roggeri (1995) the primary production of floating papyrus swamps averages an annual dry matter production of 48 - 143 ton per hectare in Africa. The papyrus communities are flanked by reed beds of Phragmites, Typha bulrushes, Pennisetum glaucocladum and then Miscanthus junceus in the shallowest waters. The Phragmites mauritianus reedbed community is widespread in the channel margins in the upper reaches of the Panhandle where the soils that have a high inorganic matter content



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condition of the vegetation in these three woodland communities will be dealt with in detail in section 5.2 in which the condition of the grass sward in these communities was quantitatively assessed in relation to the occurrence of fire in the Ramsar Site. 4.4.2 Permanent and Seasonal swamps The Permanent Swamps are located in the centre of the Delta where the water levels are the deepest and water is present year-round. This vegetation unit is made up of complex systems of vegetated flooded flats, channels, islands of varying size and madiba (lagoons). The permanent swamp vegetation is typified by emergent, floating, and submerged vegetation communities, consisting of hydrophytic grasses, sedges and aquatic species. The flood plains consist mostly of sedges and grasslands. The northern part of the swamp is characterized by communities dominated by papyrus (Cyperus papyrus), whereby more than 90% of the biomass is comprised of this giant sedge, and only at the interface of the madiba and channels are associated plants more noticeable (van der Heiden, 1992). Figure 12. Cyperus papyrus in the Permanent Swamps in the Okavango Delta. Papyrus is the largest sedge and one of the largest entirely herbaceous plants, it forms extensive, virtually monospecific stands in which it contributes more than 95% of its community phytomass. Papyrus propagates by means of ramets and it produces between 4 to 8 ramets per year (Ellery, 1988). It dominates the deepest waters and forms margins to the major channels. Water seeps through the walls of the papyrus into the back swamp, but the channels carry the bulk of the solid bedload material i.e. the sandy sediments are confined to the channels. The C. papyrus community grows in luxuriant stands and can reach heights of 4 – 5 metres. It typically comprises an entangled mass of horizontal



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conclusion is confirmed by C. mopane being very tolerant of poorly drained or alkaline soils and those with a high clay content and does not thrive on Kalahari sands. Mopane trees can obtain a maximum height of 25m when growing on rich alluvial soils and are referred to as cathedral mopane. Shorter trees are more common in areas that are poor in nutrients or have suffered extensive fire damage. Stunted mopane will form a low scrub, perhaps only 5m tall. All mopane trees are deciduous and shed their leaves in September or October. The trees themselves are an important source of food for wildlife such as elephants as the leaves have a high nutritional value, rich in protein and phosphorus, which is retained even after they have fallen from the trees. Ground cover in Mopane Woodlands is usually sparse, with slender grasses and forbs providing scant plant material (McIntyre, 2003). This is because mopane trees have a mesh of surface layer roots that compete with the grass component for moisture (Smit & Rethman, 1998). The dominant grass species occurring in Mopane Woodlands are Aristida spp., the annuals Poganarthria fleckii and Urochloa tricophus. Interspersed with either the shrub mopane or tall cathedral mopane areas are belts of dense, monospecific Philenoptera nelsii woodlands on deep sandy soils (McIntyre, 2003).

Figure 11. A fine stand of Mopane Woodland in the north eastern region of the

Okavango Delta Ramsar Site. A noteworthy feature of the grass sward in all three of these woodland vegetation types is that the grass sward is dominated by annuals with Schmidtia kalihariensis, Urochloa tricophus, Pogonarthria fleckii, Dactyloctenium giganteum, Eragrostis viscosa, Digitaria velutina, Aristida congesta and Aristida stipoides being abundant species. The current



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• Riverine forests also referred to as riparian forests are very common. They line many of Botswana’s rivers and are found throughout the Okavango-Linyanti area. Typical trees and shrubs include Diospiros mespiliformis (jackalberry),Garcinia livingstonia (mangosteen), Kigelia africana (sausage tree), Croton megalobotrys (large feverberry), Acacia nigrescens (knobthorn), Sclerocarya birrea caffra (marula), Philenoptera violacea (raintree), and various species of fig e.g. Ficus sycmorus and F. verrucucosa . Further away from the river the riparian species disappear rapidly.

Immediately south of the Gumare fault on the western side of the Okavango Delta occur the Acacia Woodlands on soils with a higher clay content extending in a broad front down to Sehitwa and Lake Ngami and then in a north easterly direction up to Maun on the distal end of the Okavango Delta. The Acacia Woodlands are dominated by Acacia species, notably Acacia erioloba, A. mellifera and A. tortilis. A. fleckii is also often encountered in this vegetation type. On the higher lying ridges particularly between Maun and Sehitwa fairly dense colonies of Terminalia prunoides are found. Due to the slightly more fertile soil several perennial grass species are found making this vegetation type suitable for livestock production but due to high livestock numbers it is severely overgrazed (McIntyre (2003). Figure 10. Acacia Woodlands in the south western region of the Okavango Delta

Ramsar Site. In the north east of the Ramsar Site extending up from Maun are the Mopane Woodlands dominated by Colophospermum mopane. Both the Burkea and Mopane Woodlands occur on soils formed by flooding during wetter periods thought to be tens of thousands of years ago. However, the soils in the north-east have a higher clay content which is responsible for the dominance of C. mopane in this vegetation unit (Mendelsohn & el Obeid (2004). This



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Baikiaea plurijuga, Schinzophyton rautanenii, Guibortia coleosperma, and Terminalia sericea. Figure 9. A typical example of Burkea Woodland in the Okavango Delta Ramsar Site In a few areas in the far north of Botswana Baikiaea plurijuga (teak) forms semi-evergreen forests on Kalahari sand. Often these woodlands occur on fossil dune-crests. As this species is not fire resistant, these stands are only found where fire is rare, and slash-and-burn type cultivation methods have never been used. The Burkea Woodlands range from open savannas to dense stands with an understory of thickets of often thorny shrubs. There are distinctive vegetation sub-groups on Kalahari sands that are described by McIntyre (2003) as follows:

• Terminalia sericea sandveld that occurs on deep, loose, unfertile sands which cover large areas of the Kalahari. The main species are Terminalia sericea and Philenoptera nelsii. These generally occur with Burkea africana and Combretum collinum.;

• Acacia erioloba woodlands also occur on sand, but often where there are fossil river valleys that have an underground supply of water throughout the year. Acacia erioloba have exceedingly long tap roots that reach this underground supply sustaining large stands of these mature trees 16 – 17m in height. They are slow growing and give good shade so do not have a dense understory;

• Acacia tortilis woodlands are not found on deep sand, instead they prefer the fine alluvium soils that water has deposited over time. Although homogeneous stand are found less often than those of Acacia erioloba a number of very distinctive flat-topped umbrella thorns can often be seen together;



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Figure 8. Location of the Acacia, Burkea and Mopane Woodlands and Seasonal and Permanent Swamps in the Okavango Delta Ramsar Site in Botswana.

4.4.1 Woodlands Commencing with the Burkea Woodlands this vegetation unit occurs on Kalahari sands extending northwards from the Gumare fault on either side of the Panhandle. The tree component of the vegetation is characterised by Burkea africana, Pterocarpus angolensis,



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Table 4. The areas and proportions of the major vegetation units in the Okavango

Delta Ramsar Site and their relationships with the original vegetation types identified and classified by Jellema, Ringrose & Matheson, (2002) at the Harry Oppenheimer Okavango Delta Research Centre in Maun.

VEGETATION UNIT ORIGINAL VEGETATION

TYPES AREA – km2 %

Acacia Woodlands i) Treed shrubland with Acacia ii) Shrubbed grassland with sagebrush; iii) Treed grassland on former floodplain; iv) Shrubbed grassland on

former floodplain.

26179

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Burkea Woodlands i) Shrubland towards dune crests with Burkea and Baikiaea;

ii) Grassed shrubland in dune valleys with Terminalia and Baphia.

11277

20

Mopane Woodlands i) Shrubbed woodland with mixed Mopane.

10806 20

Seasonal Swamps i) Dry floodplains and island interiors;

ii) Shrubbed woodland of riparian zones.

2517

5

Permanent Swamps i) Swamp vegetation with fringing emergents.

4595 8

TOTAL 55374 100 The results in Table 4 indicate that the Acacia Woodlands comprise the largest vegetation unit in the Ramsar Site and together with the Burkea Woodlands and Mopane Woodlands make up 87 % of the dryland areas with the Seasonal Swamps and Permanent Swamps forming the remaining 13 % of the total area. The location of the different vegetation units in the Ramsar Site is presented in Figure 8.



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show that besides the winds blowing predominantly from the east, strong winds in excess of 20 km/h do occur for 35 % of the time which will and can have a very significant effect on the potential for fires in the Ramsar Sites particularly during the dry late winter period i.e. August to October. 4.4 Vegetation In order to describe and assess the fire ecology of the Okavango Delta Ramsar Site a comprehensive description is required of the different types of vegetation occurring in the study site. The vegetation is a product of the edaphic and climatic environment of an area and its botanical composition and structure determines both the potential necessity for it to burn. Consequently the description of the vegetation will be conducted to facilitate the development of a practical fire management for the Ramsar Site. Due to the wide range of habitats that range from perennial swamp to semi-arid savannas the Okavango Delta Ramsar Site has a high plant/area ratio when compared to other parts of southern Africa having 1 061 different plant species (ODMP Draft Framework Plan, 2005). For purposes of management the vegetation of the Okavango Delta Ramsar Site has been simplified from the original classification of 45 vegetation types to 10 major vegetation types as developed by Jellema, Ringrose & Matheson, (2002) at the Harry Oppenheimer Okavango Research Center (HOORC) in Maun. However, for the purpose of developing a fire management plan it was necessary to simplify the classification further and use was made of the simple and practical classification by Mendelsohn & el Obeid (2004) in the book, the Okavango River viz. Acacia Woodlands, Burkea Woodlands, Mopane Woodlands, Seasonal Swamps and Permanent Swamps. This was done by combining some of the 10 vegetation types into the aforementioned units according to their general similarities in botanical composition, physiognomy, soil type and recommendations for controlled burning. The areas covered by the five major vegetation units and their relationships to the original 10 vegetation types identified by Jellema, Ringrose & Matheson, (2002) are presented in Table 4.



27

Table 2. The monthly mean, maximum and minimum relative humidities for Maun and Shakawe in the Okavango Delta Ramsar Site for the period 1967 to 1998. Data expressed in degrees celsius.

MONTH RELATIVE HUMIDITY RELATIVE HUMIDITY RELATIVE HUMIDITY RELATIVE HUMIDITY

08h00 - MAUN 14h00 - MAUN 08h00 - SHAKAWE 14h00 - SHAKAWE

Mean Max Min Mean Max Min Mean Max Min Mean Max Min

January 74 89 60 47 68 30 81 89 61 53 73 32

February 77 92 51 47 71 26 84 91 68 53 69 35

March 74 87 55 43 61 25 80 89 42 48 62 32

April 69 86 48 36 52 25 73 84 26 40 50 26

May 64 100 49 29 43 21 71 80 62 31 39 22

June 63 76 53 27 36 23 72 81 58 27 35 19

July 61 95 51 26 42 21 70 76 59 20 34 20

August 48 62 39 21 29 16 59 69 47 20 28 15

September 41 58 26 19 29 11 51 58 38 19 27 13

October 45 56 34 24 34 15 53 65 35 26 54 15

November 55 71 33 33 44 17 64 76 48 37 53 22

December 68 83 53 42 61 25 75 83 62 45 60 32

The data in Table 2 indicates that the relative humidities at Shakawe tend to be higher than at Maun. In both cases the relative humidities are higher in summer from November to March during the wet season and decrease during the dry winter season winter to a minimum during August to October. As with the temperature profile the highest fire danger will be greatest during this period during the day but decreasing significantly at night as indicated by the minimum relative humidities recorded at 08h00. Similar to the temperature profiles these relative humidity data indicate that there is ample opportunity for manipulating the intensity of fires in the Ramsar Site both for controlling wildfires fires and applying controlled burns.

4.3.5 Wind

The wind profiles for Maun and Shakawe in the Okavango Delta Ramsar Site are presented for in Table 3. Table 3. Annual percentage frequency of wind direction recorded at Maun (1968

– 1978) and Shakawe (1966 – 1969) in the Okavango Delta Ramsar Site (Tawana Land Board Report: Land Use and Land Management Plan, 2006).

DIRECTION N NE E SE S SW W NW CALM MAUN

FREQUENCY - % 12 17 20 11 6 2 3 4 25

DIRECTION N NE E SE S SW W NW CALM SHAKAWE FREQUENCY - % 8 5 21 10 8 2 3 4 39

The results in Table 3 indicate that at Maun and Shakawe 48 % and 44 % respectively of the wind blows from an easterly direction compared to 15 % and 17 % respectively from other directions during the year. Data from Tinley (1976) showed that wind speeds during the year were 5 - 13, 14 – 24 and 25 – 40 km/h for 65, 30 and 5 % of the year. These data



26

Table 1. The monthly mean, maximum and minimum air temperatures for Maun and Shakawe in the Okavango Delta Ramsar Site for the period 1967 to 1998. Data expressed in degrees celsius.

MONTH

AIR TEMPERATURE -

0C

MAUN

AIR TEMPERATURE -

0C

SHAKAWE

Mean Max Max Mean Min Min Mean Max Max Mean Min Min

January 32 36 20 12 31 35 20 18

February 32 37 20 17 31 35 20 17

March 32 35 19 17 31 34 19 17

April 31 34 16 13 30 34 16 13

May 28 31 11 8 28 30 12 7

June 25 28 8 5 26 28 7 5

July 26 28 7 5 26 28 6 4

August 29 31 10 8 29 31 9 6

September 33 35 15 13 33 35 13 11

October 34 37 19 17 34 37 18 16

November 34 37 20 7 34 37 19 13

December 33 36 20 14 33 36 20 18

The results in Table 1 indicate that the temperature profile for Maun and Shakawe is for all practical purposes similar with the hottest period being generally from September to April and the coolest period from May to August. From a fire behaviour perspective the maximum temperatures of >300C during August to October indicate that this is the period with the highest fire danger in the year because this is when generally grass fuel is at it driest and under these conditions high air temperatures promote high fire intensities. The lowest minimum temperatures occur between May and September generally at night and under these conditions the fire danger will be low resulting in less intense fires. However, any air temperature below 160C will result in a relatively cool fire and a low fire danger. These temperature data indicate that there is ample opportunity of manipulating the intensity of fires in the Ramsar Site both for controlling wildfires fires and applying controlled burns.



25

The annual inflow of water into the Okavango River recorded at Mohembo for the period 1984 to 2005 is presented in Figure 7.

12860

67846507

8694

49675482 5170

4432

6106

76197882

6491 6563

10447

7754

0

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Year

d

abab

Mean Annual Inflow - 7113 cusecsbc

aab

aba

ab

abc abcab ab

cd

abc

Figure 7. Total annual inflow of water during January to July into the Okavango River recorded at Mohembo in the Okavango Delta Ramsar Site for the period 1984 to 2005.

The results in Figure 7 show that that the greatest overall inflows of water into the Okavango River during the period 1984 to 2005 occurred in 1984 and 2004. While during a significant number of years particularly during the 1990’s the inflow of water was below average a regression analysis showed that there was no statistically significant trend for the inflow of water to have either decreased or increased during this 21 year period (r = 0.167; DF = 13; P = NS). These results indicate that the annual flow of water into the Seasonal Swamps is highly dynamic and that this in turn would cause a great variation in particularly the grass fuel loads in this vegetation unit resulting in a highly variable number and intensity of fires occurring in this vegetation unit. 4.3.4 Air temperature and relative humidity The Okavango Basin is characterized throughout by warm or hot conditions during most of the year and for much of every day. Annual temperatures throughout the area average 20oC, increasing by two or three degrees from north to south as a result of the higher solar radiation in the southern areas. When there are no clouds, temperatures can peak as high as 40oC (Mendelsohn & el Obeid, 2004). Air temperature and relative humidity data are available for Maun and Shakawe and these will be used to describe the annual profiles for these two climatic parameters in the Okavango Delta Ramsar Site. The monthly mean, maximum and minimum air temperatures and relative humidities for Maun and Shakawe for the period 1967 to 1998 are presented in Table 1 and 2.



24

deteriorating to a serious drought during 2003. Conditions improved during 2004 but were again followed by serious drought circumstances in 2005. This fortunately ended with the copious rainfall that commenced in January 2006 and continued through the late summer and autumn period during March and April. This representation of the annual rainfall it particularly pertinent to the production of grass fuel as Danckwerts (1982) found that there was a highly significant correlation between grass production and the previous twelve months rainfall. This rainfall information can therefore be used to gauge the production of grass fuel prior to the onset of the fire season in the winter and is well illustrated by the significant production of grass fuel that was produced in the Ramsar Site during the late summer and autumn period of 2006. 4.3.3 Annual flood – Okavango River The other source of moisture that influences the vegetation in the Ramsar Site are the annual flood waters entering the Okavango River at Mohembo from Namibia and Angola. The volume of water in the annual flood determines the extent to which the Seasonal Swamps are inundated by water and when it recedes the degree to which the vegetation grows and produces plant fuels available for the occurrence of fires. Preliminary data provided an initial opportunity to investigate this information. The mean monthly inflow of water between January and July for the period 1984 to 2006 is presented in Figure 6.

879

676

16501457

1182

758545

0

200

400

600

800

1000

1200

1400

1600

1800

Cu

se

sc

January February March April May June July

Month

b

ab

d

d

b

ab

a

Figure 6. Mean monthly inflow of water into the Okavango River from January to

July recorded at Mohembo in the Okavango Delta Ramsar Site for the period 1984 to 2006. Data expressed in cubic metres of water per second i.e. cusecs. Note: Different alphabetical letters indicate significant differences between mean values at P<0.05.

The results in Figure 6 indicate that for the period 1984 to 2006 the peak flood period was generally during March, which while it was not significantly different from the inflow during April these two months generally have significantly greater inflows of water than the preceding and succeeding months.



23

TWELVE MONTHS RAINFALL - 2000 - 2002

0

100

200

300

400

500

600

700

800Jan

Feb

Mar

Ap

r

May

Ju

n

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l

Au

g

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2000 2001 2002

YEAR/MONTH

PR

EV

IOU

S T

WE

LV

E M

ON

TH

S R

AIN

FA

LL

-mm

Abundant Soil Moisture,

Grass Forage & Fuel

Mean Rainfall - 446 mm

Dry SeasonDry Season

PREVIOUS TWELVE MONTHS RAINFALL - MAUN - 2003 - 2006

0

100

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Jan

Feb

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2003 2004 2005 2006

YEAR/MONTH

PR

EV

IOU

S 1

2 M

ON

TH

S R

AIN

FA

LL Abundant Soil Moisture,

Grass Forage & Fuel

Mean Rainfall - 446 mm

Drought Drought

Average Season

Figure 5. The previous twelve months rainfall recorded at Maun for the period 2000 to 2006 illustrating the highly variable nature of the seasonal and annual precipitation in the Okavango Delta Ramsar Site.

The results in Figure 5 clearly illustrate the excellent above average rainfall conditions that prevailed during 2000. This was followed by generally dry conditions during 2001 and 2002



22

rainfall gradient that exists from the moister northern sector to the drier southern sector. Detailed annual and monthly rainfall records for Maun and Shakawe are presented in Appendix 2.

110

137

99

122

67

80

24 24

5 2 1 0 0 0 0 0 3 3

1613

47

55

77

101

0

20

40

60

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120

140

ME

AN

RA

INF

AL

L -

mm

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

MONTH

MEAN MONTHLY RAINFALL MAUN & SHAKAWE

MAUN

SHAKAWE

MEAN ANNUAL RAINFALL:

Maun = 446 mm (1922 - 2006)

Shakawe = 536 mm (1932 - 2004)

Coeff. Variation = 32 %

Figure 4. Mean monthly and annual rainfall recorded at Maun and Shakawe in the Okavango Delta Ramsar Site.

The results in Figure 4 clearly illustrate the summer rainfall nature of the Ramsar Site with significant rainfall commencing in November, increasing to a peak in January and February and declining in April and May. The rainfall is highly variable with a coefficient of variation of 32% for the Ramsar Site as a whole. Research in the Eastern Cape Province of South Africa has shown that one of the most effective ways of representing the variable nature of the annual rainfall and its effect on plant growth is to plot the previous twelve months rainfall on a monthly basis and compare it with the long term mean annual rainfall for the region. These data have been calculated for the Maun region of the Ramsar Site and are presented in Figure 4 for the period 2000 to 2006.



21

formation of grey, olive or blue-coloured layers beneath the surface (Mendelsohn & el Obeid, 2004).

4.3 Climate 4.3.1 Introduction Weather conditions during the annual climatic cycle play a fundamental role in the potential for fires to occur and the intensity with which the will burn during different times of the year and different times of the day. Therefore it is necessary to present a detailed description of the annual climatic conditions in the Okavango Delta Ramsar Site. Mendelsohn and el Obeid (2004) provide a succinct description of the climate of the Okavango Basin which changes from north to south. The rainfall is three times higher in the north where the air is more humid, cloud cover is greater and evaporation rates are lower than in the southern areas around the Okavango Delta. The steady southward changes in these three features mean that the Okavango River flows progressively into drier country. In essence, the river becomes more of an oasis in the south where the surrounding environment becomes increasingly arid. All of this gives the water increasing value to people, animals and plants in the south.

These trends result from the interplay between the two major climate systems that affect the Basin’s climate. The first is the Inter-tropical Convergence Zone (ITCZ), which brings moisture from the north. Northern areas in the Basin thus receive more and earlier rain and less and less moisture remains as the tropical air moves south, resulting in reduced cloud cover and rainfall, and higher solar radiation and rates of evaporation. The ITCZ moves southward early in the summer and back north in autumn, and this is why almost all rain falls in summer. Most moisture in the ITCZ feeds into equatorial Africa from the south easterly Indian Ocean trade winds, but moist air also blows into the ITCZ from the Atlantic ocean from across the Congo Basin and northern Angola and down towards the highlands in the upper catchment. A second climate system counteracts the flow of moisture from the ITCZ. This is the zone of high-pressure anticyclone cells that lie to the south. The cells also move north and south, bringing cool and dry air to southern Africa. Interactions between the anti-cyclonic cells and the ITCZ amount to something of a contest, the southerly high-pressure cells feeding in dry air, which pushes away the warm and moist ITCZ air. The high-pressure cells shift north to dominate the Basin in winter but also during sporadic dry spells in summer, while wet summers occur when the ITCZ has pushed far south. 4.3.2 Rainfall The ODMP Draft Framework Document (2005) reports the climate in the Ramsar Site as semi-arid with rainfall averaging between 250 – 500mm per annum. Rainfall is one of the primary factors influencing plant growth and the production and accumulation of plant fuels that influence and sustain the occurrence of fires in the Ramsar Site. Long term rainfall data are available for Maun and Shakawe and are presented in Figure 2. These two rainfall stations represent the northern and southern regions of the Ramsar site and illustrate the



20

The Okavango River flows into this Kalahari Basin and is shaped by a series of tectonic faults. As mentioned earlier the distal end of the Delta is controlled by the Kunyere and Thamalakane faults, with their down-throw to the northwest and the proximal end of the Delta by the Gomare/Chobe fault with the down-throw to the southeast. The pattern of these faults delineates a graben structure, filled with alluvial sediments. This graben structure is believed to be situated at the tip of the still propagating western off-shoot of the East African rift system. Perpendicular to this Delta graben, a system of faults controls the course of the Okavango River (van der Heiden, 1992).

4.2.2 Soils Soils are important to all life in the Okavango Basin. They provide the medium from which plants obtain water and nutrients, and the properties of the soils determine what plants species are present and thus the value and diversity of vegetation communities. Properties of soils vary in terms of their depth, structure and chemical composition, and these affect how much water soils retain, the depth to which roots extend to, and what nutrients are available. The physical structure of plant communities is also influenced by soils. A plant species may be stunted in one area of shallow or sterile soil but it will grow tall in deep fertile soils elsewhere. The waters of the Okavango River are very clean and clear because most of the water filters out of sandy soils made up of largely quartz grains in the catchment. These do not easily dissolve or break-up to release soluble chemicals or tiny particles that would otherwise be washed into the river as minerals and mud. Also most of the rainwater sinks into the ground rather than running off the surface. The fine to medium arenosol sands that characterize so much of the Basin are called Kalahari sands. The sands often extend to a depth of up to 300 meters in places. Sand grains usually make up 70% of the body of the soil and 10% consists of clay and silt. There are few nutrients (especially nitrogen, potassium and phosphorus) in the sand and the porous structure means that there is little run-off or water erosion. Water drains through the body of the soil rapidly, leaving little moisture at depths to which most plant roots can reach. The fluvisols are limited to areas immediately adjacent to the Okavango River and were deposited by high water flows on the flood plains. The fluvisols in the Delta have a higher nutrient content as they have progressively accumulated nutrients over long periods. The sediments usually consist of a mix of silt, clay and fine sands. Calcisols are found in abundance along fossil drainage lines mostly at the distal end of the Delta. Layers of calcium carbonate salts lying at some depth below the surface characterize these soils, which consist mostly of fine sand and smaller portions of clay and silt. The calcium carbonate sometimes forms blocks of calcrete and potentially are quite fertile and retain water to a much greater degree than arenosols. Luvisols are also present around the edges of the Delta, and these are potentially the most fertile soils as a result of deep accumulations of clay and organic material. They are porous and usually retain high levels of moisture. The formation of gleyisols is partly due to water logging at shallow depth for some or all of the year. Prolonged water saturation in the presence of organic matter results in the



19

The Okavango River with its catchment in Angola, flows across the Caprivi Strip in Namibia and enters Botswana at the town of Mohembo in the north-western region of Botswana. Before it fans out into the Delta the rivers follows for about 95km, a narrow channel, 10 – 15km wide, known as the “Panhandle”. The river brings water from the central Angolan highlands, where rainfall is three times higher than the 450 – 500 mm/year in the Delta region. The average annual inflow at the border with Namibia at Mohembo is 10 000 million m3. Downstream from the town of Seronga, the river spills out over a large area as it divides into a number of distributary channels, forming a vast alluvial fan or classic “birds-foot” delta, but which is in fact a large, conical alluvial fan (Ellery, 2003). Where the river fans out into the Delta the low gradients (1:3 500) and dense vegetation temper the flow of the water making it fill extensive floodplains and saturate the sandy soils. The main tributaries are the Nqoga in the north-east, the Jao- Boro in the center, and the Thaoge (now extensively blocked) in the west. The narrow Panhandle and alluvial fan portions are referred to as the “Okavango Delta” and forms part of the internal drainage system known as the Kalahari Basin. The seasonal summer rains (December – February) in the catchment area, give a peak inflow in April/May, and the wave of water is known as the “flood”. Local rainfall over the Delta adds approximately 30 – 40% to this inflow. Of this total inflow, hydrological models suggest that 95% is lost through evapo-transpiration and seepage. A prominent feature of the inflow water is its purity, with a negligible suspended load, hardly any inorganic matter, no chemical pollution and a low Total Dissolved Solids (TDS) content usually in the range of 25 – 40 ppm (van der Heiden, 1992).

The seasonal floodwaters cannot be accommodated in the distributary channel systems and there is considerable overspill, forming perennial swamps in the upper delta and seasonal swamps in the lower or distal reaches of the delta. The flood wave takes approximately five months to reach the distal reaches, and the maximum aerial extent of flooding is therefore in the dry season (July – August) (Ellery, 2003). 4.2 Geology and Soils 4.2.1 Geology The geology of the Delta and catchment area of the Okavango River is well documented by several authors, notably Mendelsohn & el Obeid (2004) and Main (2000). During the break-up of Gondwanaland the margins of southern Africa were lifted to produce a rim of highlands surrounding a massive shallow basin. Part of this is the Kalahari Basin that started to fill with sediments 65 million years ago (Mendelsohn & el Obeid, 2004). During the Tertiary era, the Kalahari formed the largest area of sedimentary deposits in the southern part of Africa and was thus a collection point for all the eroded sediments that accumulated to great depths. Geologists recognize Kalahari sand by grades of sand sizes, by the material from which the sand originated, and especially by the tendency of the grains to conform to the rounded shape attributable to their wind-blown or aeolian origins. Generally, the area of Kalahari sands occurs at an altitude of about 1 000m above sea level (Maine, 2000).



18

CHAPTER 4

4. STUDY SITE 4.1 Location and Description The Okavango Delta Ramsar Site is situated at the northern most edge of the Kalahari Desert in north western Botswana, in the Ngamiland Province which borders on the Caprivi Strip of Namibia immediately to the north. It is 55 374 km2 in extent and the Delta portion of the Ramsar Site comprises approximately 4595 km2 of permanent swamp and 2517 km2 of seasonal swamp (ODMP Report: Development of the Vegetation Framework Management Plan, 2005) depending on the size of the annual flood waters (Bonyongo, 1999), making it one of the largest Ramsar wetlands in the world (Tacheba, 2002).

Map Sources: Mendelsohn & el Obeid, 2002 ODMP

Figure 3. Location of the Okavango Delta Ramsar Site in Ngamiland Province in north western Botswana.

The area is characterized by Kalahari sandveld that covers much of central and southern Africa and is flat to undulating with an overlay of aeolian Kalahari sandbeds that can reach a depth of up to 300 meters. The present day Okavango Delta is an alluvial fan, its shape governed by tectonic faults. The distal end of the Delta is controlled by the two northeast-southwest trending faults, the Kunyere and Thamalakane faults, with the down-throw to the northwest. The proximal end of the Delta is limited by a third parallel fault, the Gumare/Chobe fault with the down-throw to the southeast. The pattern of these faults delineates a graben structure, filled with alluvial sediments. This graben structure is believed to be situated at the tip of the still propagating western off-shoot of the East African rift system. Perpendicular to this Delta graben, a system of faults controls the course of the Okavango River (van der Heiden, 1992).

Angola

Botswana

AFRICA



17

vegetation using ecological criteria that have been developed in similar vegetation communities for this purpose elsewhere in southern Africa.



16

during the past century. At the turn of the century the Serengeti-Mara area was described as an open grassland with lightly wooded patches, much as it is today. Following the great rinderpest epidemic of 1890, human and animal populations are thought to have been reduced to negligible numbers in the Serengeti-Mara region. Fires were infrequent due to the low human populations and elephant numbers were low having suffered from heavy ivory poaching during the previous decades. Over the next 30 to 50 years these prevailing conditions of low fire frequencies and low elephant numbers saw the establishment of dense woodlands and thickets. This woody vegetation provided ideal habitat for infestations of the tsetse fly which further prevented any significant human settlement within the Serengeti-Mara ecosystem. Consequently by the early 1940’s the area had become densely wooded and the Serengeti National Park and the Masai Mara National Reserve were characterised by dense woody vegetation and remained in this condition for over 20 years. These woodlands began to decline significantly during the late 1950’s and early 1960’s in response to two factors. Firstly there was a marked increase in the frequency of burning as a result of the dramatic increase in the human population that was recovering from the secondary effects of the rinderpest epidemic. In addition the low ungulate populations were unable to reduce the standing crop of grass particularly with the unusually high rainfall experienced in the late 1950’s and early 1960’s. This resulted in increased burning by Masai pastoralists to create better grazing for their livestock, tribesman used it to facilitate hunting, some fires were inadvertently ignited by honey hunters and European hunters used fire to attract game. The resultant high intensity fires proved devastating and helped to clear the area of bush and attract ungulates to the highly nutritious grazing created by the fires. The other effect of the increased human population was to compress elephant populations into the protected conservation areas. The Serengeti-Mara woodlands declined accordingly in response to increased utilization by elephants similar to what had occurred in other parts of Africa when elephant numbers increased to very high densities. The decline in the area of woodland in the Mara was greatest during the period 1961 to 1967 but continued into the 1980’s. Subsequently the situation changed in the Serengeti where the elephant population declined by 81% (2 460 vs 467) between 1970 and 1986 as a result of poaching and resulted in the recovery of the woodland vegetation. Conversely the elephant numbers continued to increase in the Mara due to immigration and natural population growth. These changes in elephant densities have also been accompanied by a steady increase in the wildebeest population which has risen from 250 000 in the 1960’s to its current level of 1.5 million resulting in a decline in the frequency and intensity of fires with lower rainfall also contributing to this phenomenon. The situation at present is that woodland vegetation is increasing in the Serengeti in response to low elephant densities and reduced frequencies and intensities of fires. Conversely in the Mara the woodlands continue to decline and the Themeda dominant grasslands are being maintained by the large number of resident elephants despite a decline in the frequency and intensity of fires. 3.5.6 Discussion This general overview of the effects of fire in African grasslands and savannas provides the means of determining whether the research findings that have been obtained elsewhere in southern Africa are also applicable to the arid savannas of Botswana in general, and the Okavango Delta Ramsar Site in particular. This will be done by reviewing the local scientific literature on the effects of fire in the Ramsar Site and also by assessing the condition of the



15

vegetation with a fairly closed canopy. The fire sensitive tree species Ceiba pentandra became dominant (Carson & Abbiw, 1990). Similar results have been obtained in the Lamto Reserve in the Ivory Coast which receives a high mean annual rainfall of 1 300 mm and forms part of the Guinea savanna immediately adjacent to the deciduous rain forest. The savanna vegetation is subjected to annual burning during the middle of the dry season. In a study investigating the exclusion of fire for 13 years it was found that after eight years the open savanna rapidly changed into a dense closed formation and after 13 years the first signs of forest developing occurred in the form of seedlings and saplings. This led to the conclusion that in all the burnt savannas of Lamto the pressure of forest elements on savanna vegetation is very high and the exclusion of fire initiates the development of forest (Menaut, 1977). Similar trends have been found in the more arid savannas (500 - 700 mm p.a.) in southern Africa where in the Kruger National Park the exclusion of fire caused both an increase in the density and size of tree and shrub species (van Wyk, 1971). The effect of frequency of burning on forage production has not been intensively studied in Africa and only limited quantitative data are available. The general conclusion is that the immediate effect of burning on the grass sward is to significantly reduce the yield of grass during the first growing season after burning but the depressive effect disappears during the second season (Tainton & Mentis, 1984; Trollope, 1984). The effect of frequency of burning on the quality of forage is that generally frequent fires improve and maintain the nutritional quality of grassland particularly in high rainfall areas making it highly attractive to grazing animals. This phenomenon has been recorded throughout the savanna and grassland areas of Africa (West, 1965; Tainton et al, 1977; Moe, et al., 1990; Munthali & Banda, 1992; Schackleton, 1990). West (1965) stated that the fresh green shoots of new growth on burnt grassland are very high in protein and quotes Plowes (1957) who found that the average crude protein content of 20 grasses after burning at the Matopos Research Station in Zimbabwe was 19%. This is approximately twice the protein content of mature grasses that have not been burnt at the end of the dry season. There is apparently no information available on the effect of frequency of burning on the production and quality of browse by bush in the savanna areas. 3.5.5 Interactions between fire and herbivory Utilization of vegetation by herbivory after burning can have a highly significant effect on the botanical composition and structure of vegetation. An excellent example of the significant effect of the interaction of wild ungulates and fire on vegetation is illustrated from research reported upon by Dublin (1995) in the Serengeti-Mara ecosystem in Tanzania and Kenya. The Serengeti-Mara ecosystem is an area comprising 2.5 million hectares situated on the border between Kenya and Tanzania southeast of Lake Victoria. It has a rainfall gradient from 500 mm per annum in the dry south-eastern plains to 1 200 mm per annum in the moist northwest region in Kenya (Sinclair, 1995). It constitutes one of the last natural ecosystems in Africa and is famous for its annual migration of over a million wildebeest. Fire and herbivory are very important factors in the functioning of this ecosystem and the interaction of these two factors has a highly significant effect on the composition and structure of the vegetation. Dublin (1995) states that this ecosystem has experienced major vegetation changes in its recent history, alternating between open grassland and dense woodland



14

3.5.4 Frequency of burning The effect of frequency of burning on vegetation is influenced by event-dependent effects and interval-dependent effects (Bond & van Wilgen, 1996). The event dependent effects occur at the time of the fire and are influenced by the type and intensity of the burn and the physiological state of the vegetation at the time of the fire. The interval dependent effects are influenced by the treatment and growing conditions that occur during the interval between the burns. These two overall effects tend to confound the interpretation of the effect of frequency of burning and must be borne in mind when reporting on the effect of frequency of burning. Frequency of burning has a marked effect on the botanical composition of the grass sward with species like Themeda triandra being favoured by frequent burning and Tristachya leucothrix being favoured by infrequent burning in the moist grasslands of Kwazulu-Natal Province in South Africa (Scott, 1971; Dillon, 1980). Similar results have been obtained in the arid savannas of the Eastern Cape Province in South Africa where it was found that frequent burning favours an increase in Themeda triandra and a decrease in Cymbopogon plurinodis (Robinson, Gibbs-Russell, Trollope and Downing, 1979; Forbes & Trollope, 1990). In East Africa Pratt & Gwynne (1977) reported that Themeda triandra is a common constituent of grasslands in the Central Highlands of Kenya on undulating plateau and mountain flanks where fires are regular occurrences and the grazing pressure is not too high. Where fires are infrequent or absent the upland grassland tends to become dominated by Pennisetum schimperi and Eleusine jaegeri which are coarse, tufted species of very little value as grazing. These are interval dependent effects of frequency of burning because T. triandra is sensitive to low light conditions that develop when the grass sward is not defoliated and this species rapidly becomes moribund during extended intervals between fires. Conversely species like T. leucothrix and C. plurinodis are not as sensitive to low light conditions and survive extended periods of non-defoliation. Conflicting results have been obtained on the effect of frequency of burning on bush. Kennan (1971) in Zimbabwe and van Wyk (1971) in the Kruger National Park in South Africa, both found that there were no biologically meaningful changes in bush density in response to different burning frequencies. In the False Thornveld of the Eastern Cape in South Africa Trollope (1983) found that after ten years of annual burning the density of bush increased by 41 per cent, the majority of which were in the form of short coppicing plants. Conversely Sweet (1982) in Botswana and Boultwood & Rodel (1981) in Zimbabwe found that annual burning resulted in a significantly greater reduction in the density of bush than less frequent burning. It is difficult to draw any general conclusions from these contradictory results except to note that in all cases significant numbers of trees and shrubs bushes were present even in the areas burnt annually, irrespective of whether they had decreased or increased after burning. These very variable results would suggest that the effect of frequency of burning on woody vegetation is more an event-dependent effect where factors like the type and intensity of fire have had highly significant individual effects overshadowing the effect of frequency of burning per se. On the contrary the withdrawal of fire for extended periods of time appears to have a more predictable effect. For example on the Accra Plains in south-eastern Ghana protection of moist savanna from fire for 29 years has resulted in the development of a forest type



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3.5.3 Season of burning Very little published quantitative information is available on the effect of season of burning on the grass sward. West (1965) stressed the importance of burning when the grass is dormant. Scott (1971) quoted data from the Southern Tall Grassveld of KwaZulu-Natal Province in South Africa where the mean grass basal cover of plots burnt in autumn, late winter and after the first spring rains for a period exceeding 20 years, was 12.8, 13.0 and 14.4 per cent respectively. The absence of large differences in the mean basal cover obtained with these different seasons of burning indicated that for all practical purposes burning when the grass sward is dormant in late winter or immediately after the first spring rains has very little difference in effect on the grass sward. This conclusion is supported by Tainton, Groves and Nash (1977), Dillon (1980) and Everson, Everson, Dicks & Poulter (1988) who also found that burning before or immediately after the first spring rains in KwaZulu-Natal Province had essentially the same effect on the recovery of burnt grassland. Conversely, if the grass sward is burnt later in the season when it is actively growing it causes a high mortality of tillers of Themeda triandra, resulting in a significant reduction in the abundance of this species (Dillon, 1980; Everson, Everson, Dicks & Poulter, 1988). The effect of season of burning on the recovery of grass was also investigated in the arid savannas of the Eastern Cape Province in South Africa (Trollope, 1987). This comprised determining the effect of burning the grass sward in late winter, spring, late spring and early summer. The results showed that burning in late winter consistently resulted in a significantly better recovery in the grass sward during the first growing season after the burn than the other treatments. This effect was still present during the second growing season but was not as evident as during the first growing season. Conversely the early summer burns that were applied when the grass was actively growing had a significantly depressive effect (P < 0.01) throughout the recovery period on the regrowth of the grass sward in relation to the other treatments. Thus the overall effect of the treatments was that burning when the grass was actively growing adversely affected the recovery of the grass sward when compared with burning when the grass was dormant. Season of burning also has an effect on the botanical composition of the grass sward. It was found in Kwazulu-Natal Province in South Africa that Themeda triandra declined after burning in autumn in comparison to burning in winter and spring whereas Tristachya leucothrix responded in the exact opposite manner (Bond & van Wilgen, 1996). It is difficult to determine the effect of season of burning on bush because generally it is confounded with fire intensity. This is because when the trees are dormant in winter the grass is dry and supports intense fires whereas when the trees are actively growing during summer the grass is green and the fires are much cooler. Suffice it so say that West (1965) postulated that trees and shrubs are probably more susceptible to fire at the end of the dry season when the plant reserves are depleted due to the new spring growth. However, the results of Trollope, Potgieter & Zambatis (1990) showed that the mortality of bush in the Kruger National Park in South Africa was only 1.3 percent after fires that had been applied to bush ranging from dormant to actively growing plants. Therefore it would appear that bush is not sensitive to season of burn.



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Bush is very sensitive to various types of fires because of differences in the vertical distribution of the release of heat energy. Field observations in the Kruger National Park and in the Eastern Cape Province of South Africa and quantitative results from the central highlands of Kenya indicate that crown and surface head fires cause the highest topkill of stems and branches of trees and shrubs as compared to back fires (Trollope & Trollope, 1999). The reason for this is that head fires generate greater flame heights than back fires thus resulting in the fire susceptible growing points of taller trees and shrubs being above the flaming zone of combustion during back fires as compared to head fires. 3.5.2 Fire intensity Fire intensity refers to the release of heat energy per unit time per unit length of fire front (kJ/s/m) (Byram, 1959). There have been very limited attempts in African savannas and grasslands at quantitatively measuring the intensity of fires and relating fire intensity to the response of herbaceous and woody plants in terms of mortality and changes in physical structure. Such research appears to be limited to studies conducted in the savanna areas of South Africa. The effect of fire intensity on the recovery of the grass sward after burning was investigated in the arid savannas of the Eastern Cape. After a series of fires ranging in intensity from 925 to 3 326 kJ/s/m (cool to extremely intense) there were no significant differences in the recovery of the grass sward at the end of the first or second growing seasons after the burns (Trollope & Tainton, 1986) leading to the conclusion that fire intensity has no significant effect on the recovery of the grass sward after a burn. This is a logical result as otherwise intense fires would not favour the development and maintenance of grassland. The effect of fire intensity on bush has been studied in the arid savannas of the Eastern Cape Province (Trollope & Tainton, 1986) and the Kruger National Park (Trollope, Potgieter & Zambatis, 1990) in South Africa and in the central highlands of Kenya (Trollope & Trollope, 1999). This comprised determining the mortality of plants and secondly the total topkill of stems and branches of bush of different heights. The results indicated that bush is very resistant to fire alone and in the Eastern Cape Province in South Africa the mortality of bush after a high intensity fire of 3 875 kJ/s/m was only 9,3 per cent. In the Kruger National Park the average mortality of 14 of the most common bush species subjected to 43 fires ranging in fire intensity from 110 to 6 704 kJ/s/m was only 1,3 per cent. In Kenya the mean mortality of trees and shrubs was only 4.4%. In all cases the majority of the trees that suffered a topkill of stems and branches coppiced from the collar region of the stem. Therefore it can be concluded that, generally, the main effect of fire on bush in the savanna areas is to cause a topkill of stems and branches forcing the plants to coppice from the collar region of the stem. However, research in the Kruger National Park and the Eastern Cape Province in South Africa, the central highlands of Kenya and in the Serengeti National Park has also shown that bush becomes more resistant to fire as the height of the trees and shrubs increase (Trollope & Tainton, 1986; Trollope, Potgieter & Zambatis, 1990; Trollope & Trollope, 1999).



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modus operandi for controlled burning. In the context of controlled burning in the Okavango Delta Ramsar Site the significance of these results is that the intensity of a controlled burn can be significantly increased or decreased merely by manipulating the type of fire through the ignition procedure. This will be dealt with later in detail in the section on controlled burning. Finally great strides have been made in the study of fire behaviour and it is now possible to formulate realistic guidelines for land users in terms of type and intensity of fires. 3.5 Effects of Fire in African Grasslands and Savannas Africa is referred to as the Fire Continent (Komarek, 1971) because of the widespread occurrence of biomass burning, particularly in the savanna and grassland biomes. The capacity of Africa to support fire stems from the fact that it is highly prone to lightning storms and has an ideal fire climate comprising dry and wet periods. It also has the most extensive area of tropical savanna in the world, which is characterised by a grassy understory that becomes extremely inflammable during the dry season. As a result of the aforementioned factors fire is regarded as a natural ecological factor of the environment that has been occurring since time immemorial in the savanna and grassland areas of Africa. Its use in the management of vegetation for both domestic livestock systems and in wildlife conservation is widely recognized and used throughout the African continent (Tainton, 1999). Fire ecology refers to the response of the biotic and abiotic components of the ecosystem to the fire regime i.e. type and intensity of fire and the season and frequency of burning (Trollope, et al, 1990). To follow is an overview of the known effects of the fire regime on grass and bush vegetation in Africa based on research results. 3.5.1 Type of fire The most common types of fire in grassland and savanna areas are surface fires (Trollope, 1983) burning either as head or back fires. Crown fires do occur in savanna but only under extreme fire conditions. Generally under these conditions they occur as passive crown fires characterised by the “torching” of individual trees rather than as active crown fires that are sustained by more abundant and continuous aerial fuels. The significance of the effect of type of fire on plants is that it determines the vertical level at which heat energy is released in relation to the location of bud tissues from which meristematic sites the plants recover after burning. Trollope (1978) investigated the effects of surface fires, occurring as either head or back fires, on the grass sward in the arid savannas of the Eastern Cape of South Africa. The results showed that back fires significantly (P < 0.01) depressed the regrowth of grass in comparison to head fires because a critical threshold temperature of approximately 95o C was maintained for 20 seconds longer during back fires than during head fires. It was also found that more heat was released at ground level during the back fires compared to the head fires, therefore the shoot apices of the grass plants were more adversely affected during the back fires than during the head fires.



10

The regression equation is based on the following statistics:

Number of cases = 200 Multiple correlation coefficient (R) = 0.7746 (P < 0.01). Coefficient of determination (R2) = 0.6000.

The aforementioned fire intensity model developed in South Africa was tested in the central highlands of Kenya in the overall range type classified as "Scattered Tree Grassland: Acacia-Themeda" by Edwards & Bogdan (1951). The results showed that the fire intensity model was able to predict the difference between high and low intensity fires and the model provided a satisfactory basis for formulating guide lines for controlled burning based on fire intensity (Trollope & Trollope, 1999).

3.3 Behaviour of Different Types of Fires One of the components of the fire regime is the type of fire. Its inclusion as part of the fire regime is justified on the basis that different types of fires behave differently and have contrasting effects on the vegetation. In the grassland and savanna areas surface fires burning as head and back fires are the most common types of fire. The behaviour of surface fires burning with and against the wind were investigated by Trollope (1978) in the savanna areas of the Eastern Cape Province in South Africa. The results of the research showed that head fires were on average approximately seven times more intense than back fires. The intensity of the head fires was also far more variable than that of the back fires. They ranged from very cool fires to extremely hot fires, whereas the back fires were all very cool. Therefore the intensity of head fires was far more significantly influenced by the environmental conditions prevailing at the time of the burn than the back fires. 3.4 Conclusions Notwithstanding the difficulties of studying fire behaviour the information that has been presented emphasizes the importance of this aspect of fire ecology. The identification of fire intensity as an ecologically meaningful parameter describing the behaviour of vegetation fires has enabled the quantification of fire behaviour and has provided a means of quantifying the effects of fire on the biotic components of grassland and savanna ecosystems. The development of a simple fire intensity model based on easily measured environmental factors has also provided an objective means of formulating quantitative guidelines involving fuel loads, fuel moisture, air temperature, relative humidity and wind speed for controlled burning. Comparison of the behaviour of head and back fires also clearly illustrates the differences between these two types of fires. The contrasts in fire intensity have great biological significance as they indicate the rate at which heat energy is released during head and backfires and provide a greater understanding of the effects of fire on the ecosystem. The contrasting behaviour of head and back fires is also pertinent to the formulation of safety procedures for controlled burning. The fire behaviour data illustrate how by merely altering the type of fire a burn can be converted from a cool fire into a raging inferno under the same fuel and atmospheric conditions. These results provide the rationale for the practical application of controlled burns and the safety procedures that are incorporated in the



9

positively correlated with fuel moisture (Wright & Bailey, 1982) and therefore plays an important role in controlling the flammability of fine fuels (Brown & Davis, 1973).

3.1.2.5 Wind The combustion rate of a fire is positively influenced by the rate of oxygen supply to the fire (Brown & Davis, 1973; Cheney, 1981) hence the effect of wind speed on fire intensity. Wind also causes the angle of the flames to become more acute. With increased wind velocities the flames are forced into the unburnt material ahead of the fire front resulting in more efficient preheating of the fuel and greater rates of spread in surface head fires (Luke & McArthur, 1978; Cheney, 1981). 3.1.2.6 Slope

Slope significantly influences the forward rate of spread of surface fires by modifying the degree of preheating of the unburnt fuel immediately in front of the flames. In a head fire, this is achieved, as with wind, by changing the flames to a very acute angle and with slopes exceeding 15 - 200 the flame propagation process involves almost continuous flame contact. Conversely a down slope decreases the rate of spread of surface head fires (Luke & McArthur, 1978) and at low wind speeds has the effect of converting a head fire into a back fire. Experience gained in the U.S.A. indicates that the increasing effect of slope on the rate of spread of head fires doubles from a moderate slope (0 - 220) to a steep slope (22 - 350) and doubles again from a steep slope to a very steep slope (35 - 450) (Luke & McArthur, 1978).

3.2 Fire Intensity Model Based on research conducted in the Eastern Cape Province and Kruger National Park in South Africa (Trollope, 1983; Trollope & Potgieter, 1985) a fire intensity model was developed using a multiple regression analysis for surface head fires burning in grassland and savanna areas. The model was based on the effects of fuel load, fuel moisture, relative humidity and wind speed on fire intensity. Air temperature was considered but not included in the model because it is significantly correlated with relative humidity. The multiple regression equation for predicting fire intensity is:

FI = 2729 + 0.8684 x1 - 530 √√√√x2 - 0.907 x23 - 596 1/x4

where: FI = fire intensity - kJ/s/m

x1 = fuel load - kg/ha x2 = fuel moisture - % x3 = relative humidity - % x4 = wind speed - m/s



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3.1.2.1 Fuel load Fuel load is regarded as one of the most important factors influencing fire intensity because the total amount of heat energy available for release during a fire is related to the quantity of fuel (Luke & McArthur, 1978). Assuming a constant heat yield, the intensity of a fire is directly proportional to the amount of fuel available for combustion at any given rate of spread of the fire front (Brown & Davis, 1973). The most practical and efficient method for estimating grass fuel loads is with the disc pasture meter developed by Bransby & Tainton (1977). The calibration for the general use of the disc pasture meter is that developed in the Kruger National Park in South Africa. This calibration has been found to be not statistically different from calibrations that have been developed in grassland and savanna areas in the Eastern Cape Province of South Africa, the central highlands of Kenya, the Ngorongoro Crater in Tanzania and the Caprivi region in Namibia. The generalized calibration that can be used is:

y = -3019 + 2260 √x

where: y = mean fuel load - kg/ha;

x = mean disc height - cm.

3.1.2.2 Fuel moisture Fuel moisture has a negative effect on fire intensity and is a critical factor in determining the intensity of a fire because it affects the ease of ignition, the quantity of fuel consumed and the combustion rate of the different types of fuel. The most important influence of fuel moisture on fire behaviour is the smothering effect of the water vapour released from the burning fuel. It reduces the amount of oxygen in the immediate proximity of the burning plant material thus decreasing the rate of combustion (Brown & Davis, 1973). Luke & McArthur (1978) distinguish between the moisture content of living plant tissue and cured plant material. The former varies gradually in response to seasonal and climatic changes whereas cured plant material is hygroscopic and the moisture content is affected on an hourly and daily basis mainly by absorption and adsorption in response to changes in the relative humidity of the adjacent atmosphere.

3.1.2.3 Air temperature Air temperature has a positive effect on fire intensity and its direct effect is to influence the temperature of the fuel and therefore the quantity of heat energy required to raise it to its ignition point (Brown & Davis, 1973). Air temperature also has indirect effects via its influence on the relative humidity of the atmosphere and moisture losses by evaporation (Luke & McArthur, 1978).

3.1.2.4 Relative humidity The relative humidity of the atmosphere has a negative effect on fire intensity by influencing the moisture content of the fuel when it is fully cured (Luke & McArthur, 1978). It is



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CHAPTER 3 3. OVERVIEW OF THE FIRE ECOLOGY OF AFRICAN GRASSLANDS AND SAVANNAS 3.1 Fire Behaviour The effect of fire on natural ecosystems involves the response of living organisms to the release of heat energy through the combustion of plant material. The manner in which, and the factors that influence the release of heat energy, involves the study of fire behaviour. In Africa there is a serious deficiency of knowledge concerning the behaviour of fires and this is particularly applicable to the savanna and grassland areas of the continent. Virtually no attempt has been made to quantify the dynamics of the release of heat energy during a fire and the subsequent response of plants to it. This general statement is equally true for the different grassland, savanna and wetland systems in Botswana in general and the Okavango Delta Ramsar Site in particular. The determination of such relationships helps explain many of the apparently inexplicable effects of fire that are often cited in the literature. 3.1.1. Fire intensity In the study of fire behaviour various parameters have been developed to quantitatively describe the behaviour of fires burning in vegetation but in this discussion only those parameters that are pertinent to the effect of fire on the flora will be considered. Research on fire behaviour in the savanna areas of the Eastern Cape Province and the Kruger National Park in South Africa lead/led to the conclusion that the most appropriate parameter to use for describing fire behaviour and its effects on the vegetation was fire intensity as defined by Byram (1959) i.e. fire intensity is the release of heat energy per unit time per unit length of fire front. Numerically it is the product of the available heat energy and the forward rate of spread of the fire front and can be expressed as the equation:

I = H x w x r

Where: I = fire intensity - kJ/s/m; H = heat yield - kJ/kg; w = mass of available fuel - kg/m2; r = rate of spread of the fire front - m/s.

3.1.2. Factors influencing fire intensity The factors influencing the behaviour of fires will be discussed in terms of those variables that should be considered when applying controlled burns. A review of the literature reveals that these can be listed as fuel load, fuel moisture, air temperature, relative humidity and wind speed (Brown & Davis, 1973; Luke & McArthur, 1978; Cheney, 1981; Leigh & Noble, 1981; Shea, Peet & Cheney, 1981; Wright & Bailey, 1982).



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that one does not have legal rights over. Clarify the administration of the Act and the requirements by relevant stakeholders for being able to use controlled burning as a range management practice in terms of the Act;

2.6 Involve Botswana Government staff and other relevant stakeholders in the development of the fire management plan thereby ensuring the necessary transfer of skills and knowledge for the management of fire in the Okavango Delta Ramsar Site.

In order to fulfill the objectives and develop a fire management plan the following process of consultation was under taken.

Government

ODMP

Identification of problem(s)

Objective(s)

Solution(s)

Consultants Stakeholders

Okavango Delta

Ramsar Site

Okavango Delta

Ramsar Site

Dept Forestry & Range Resources

Figure 2. The consultation process undertaken for developing the Fire Management

Plan for the Okavango Delta Ramsar Site.



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CHAPTER 2

2. OBJECTIVES OF THE PROJECT The overall objective of the project was to gain an understanding of the impact of fire in the Delta and based on literature reviews, interviews with stakeholders and an assessment of the condition of the vegetation, develop a fire management plan for the Okavango Delta Ramsar Site in order to ensure sustainable use and management of the vegetation in the Delta and to control injudicious burning and wildfires occurring in this unique African wetland ecosystem. The specific objectives of the project were to: 2.1 Determine the basic causes of fire in the Delta and identify those that are natural and

those that are of anthropogenic origin and where possible to establish to what extent anthropogenic fires are accidental or deliberate;

2.2 Determine the effects of fires on the major landscapes/vegetation types and the associated fauna;

2.3 Develop simple and practical quantitative ecological criteria that can be used to differentiate between areas that can be considered for controlled burning and areas where fire should be excluded to safeguard the productivity, sustainability and biodiversity of the ecosystem. Such criteria based on the botanical composition, cover and standing crop of the vegetation have been successfully developed and used for fire management in other savanna areas in southern and east Africa. Consequently one of the primary objectives of this study in the Okavango Delta Ramsar Site will be to develop similar ecological criteria that can be used to both control the occurrence of wildfires and to provide clear guidelines for the use of controlled burning as an ecologically acceptable management practice for the different systems of land use in the Ramsar site;

2.4 Use existing maps obtainable from the Harry Oppenheimer Okavango Research Center (HOORC), the vegetation classification by Mendelsohn & el Obeid in 2004 and quantitative ecological criteria for identifying vegetation types in the Ramsar site with different potentials for supporting fires as a means of effectively preventing, controlling or managing wild fires with limited fire fighting resources. Based on data collected during field trips produce a fire management plan that:

• States the ecologically permissible and non-permissible reasons for using fire as a range management practice;

• Describes the fire regime in terms of type and intensity of fire and season and frequency of burning recommended for the permissible reasons for using fire as a range management practice;

• Describes the post-fire range management recommended for areas used for different systems of land use;

• Describes the practical procedures to be followed and equipment to be used for the successful and safe application of controlled burning;

• Identifies aspects of the fire regime and its effects on the ecosystem that require further research;

2.5 Address the requirements of the Herbage Preservation Act relating to controlled burning that states that it is illegal and punishable by law to set the rangeland on fire



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al, 1998) and in the Serengeti National Park (Dublin, 1995). Experience gained by field personnel of the Department of Wildlife and National Parks (DWNP) support this concept as they suggest that the Okavango Delta system is driven by an interaction of available water, fire and elephants (Personal Communication, 2006). Therefore in order to develop a meaningful fire management plan for the Okavango Delta Ramsar Site it is first necessary to develop a comprehensive description of the fire regime in the Ramsar Site i.e. type and intensity of fire and season and frequency of burning. This must be followed by an investigation of the fire ecology of the Ramsar Site describing the effects of type and intensity of fire and season and frequency of burning on the vegetation and fauna if possible. A description of the general fire regime and fire ecology will be possible for the drylands of the Ramsar Site (Mopane, Acacia & Burkea Woodlands) and will be achieved by drawing on the published effects of fire in southern African savannas and studying the reported investigations on fire in the Delta by Heinl (2005), Tacheba (2002), Cassidy (2003), Tlotlego (2004) and Banda (2004). This will be more difficult for the Permanent and Seasonal Swamps because of the lack of long term research data both on the fire regime and fire ecology of these two vegetation units. However, indications on the season and frequency of burning will be obtained from satellite data analyzed and summarized by Cassidy (2003), Heinl (2005), Tacheba (2002) and Tlotlego (2004). In addition to this information a preliminary assessment of the condition of the vegetation in relation to fire will be conducted in the aforementioned major vegetation types. This will be done using, where applicable procedures and quantitative criteria that have been developed in southern and east Africa to assess whether there is an ecological requirement and necessity for controlled burning as a management practice for the vegetation in its current and potential condition. Finally personal interactive surveys will be conducted based on a standardized questionnaire with appropriate representatives from traditional communities, tourism sector stakeholders and relevant Government departments and divisions to determine their perspectives on the current reasons for burning and the fire regime and fire ecology of the Okavango Delta Ramsar Site.



3

• Tacheba (2002) determining the extent and season during which fires occurred during September 2000 and 2001 and the effects of these fires on the structure and biodiversity of plant communities in the wetlands of the Okavango Delta;

• Cassidy (2003) investigating the livelihoods and spatial dimensions of anthropogenic burning in the Okavango Panhandle, Heinl (2005) studying fire and its effects on vegetation in the Okavango Delta,

• Tlotlego (2004) investigating the effects of fire threatening the production of thatch grass in the Panhandle;

• Banda (2004) researching the influence of burning on microorganisms along the Boro route in the Okavango Delta.

While all studies are highly commendable and significant scientific contributions to describing and understanding the fire ecology of the Okavango Delta they are all short-term investigations that cannot fully describe the long-term effects of burning on the vegetation in the different vegetation types in the Delta. Considerable information is available on the general effects of the fire regime on the non-flooded vegetation types in the Delta Ramsar Site from research conducted in the arid savannas elsewhere in southern Africa (Bond & van Wilgen, 1996; Trollope, 1982; Trollope, 1984; Trollope, 1999; van Wilgen et al, 2003). This opinion is supported by Heinl (2005) who concluded that the general response of the vegetation to fire in the drylands of the Okavango Delta is similar to the savannas elsewhere in southern Africa. However, long-term data on the effects of fire on the vegetation in the Permanent and Seasonal Swamps is not available. The concern for the negative impact of fire on the vegetation specifically in the dry sand veld areas is supported by a preliminary investigation conducted in 2005 by two of the consultants (Dr & Mrs Trollope) in Concession Area No 34 located north east of Maun and contiguous to the southern border of the Moremi Game Reserve. Observations showed that wildfires that had occurred during 2005 in Mopane Woodland with a sparse cover of pioneer grass species dominated by Aristida congesta, the herbaceous layer had been very negatively affected and converted into extensive areas devoid of herbaceous vegetation and prone to wind erosion. This observation led to the conclusion and recommendation that the Mopane woodlands in particular should be excluded from burning and wildfires should be controlled especially in normal to below average rainfall years as a matter of priority in this vegetation type. (Trollope & Trollope, 2005). Therefore an important element in the sustainable management of vegetation in the Delta is the development of a comprehensive fire management plan to control frequent wild fires that threaten to seriously damage and alter the vegetation resources and impact on rare and endangered species e.g. slaty egret and sititunga habitats. However, it should be borne in mind that the often perceived negative impacts of fire on the vegetation are the combined interaction of fire and herbivory. Therefore considering that the human population and its associated livestock numbers have increased considerably since early times, the perceived negative impacts of fire in the Delta region may also have been magnified by the interaction of fire and livestock, both domestic and wildlife, rather than fire per se. This possibility also applies to the wildlife areas where the severe impact of increasing numbers of elephants in the Delta system may also have combined with fire to escalate the pressure on the Okavango Delta ecosystem. The interacting effects of fire and herbivory have been clearly and well documented in the Kruger National Park (Trollope et



2

Arising from this contractual commitment and in order to ensure the Okavango Delta’s conservation and wise use, the Okavango Delta Management Plan (ODMP) project proposal was drawn up in 2002 as a means: “to integrate resource management for the Okavango Delta that will ensure its long term conservation and that will provide benefits for the present and future well being of the people, through sustainable use of its natural resources”. The strategy that was adopted to achieve the implementation of the ODMP was amongst other things, to collectively create a greater sense of responsibility and accountability amongst communities and in existing institutions with a mandate to manage the Delta and its resources. In doing so, 10 components and their respective responsible institutions were identified. One of the primary and important components listed in the ODMP report was that of Vegetation Resources and its management is the responsibility of the Department of Crop Production (DCP) in the Ministry of Agriculture and the Department of Forestry and Range Resources in the Ministry of Environment, Wildlife and Tourism. This component has the responsibility “to ensure sustainable management of the Okavango Delta vegetation initiated and supported by providing accurate data and assisting in resolving vegetation management conflicts” This includes considering the ecology and use of fire in the Okavango Delta Ramsar Site where generally wild fires are perceived to be an increasing problem in terms of their frequency, severity and uncontrolled nature. This issue has been raised by both communities and tourism sector stakeholders during consultation meetings and their concerns are echoed by the large areas of the Delta, both in the wetland portions and the surrounding dry sand veld, that are seen to be burnt each year (Terms of Reference: Development Of A Fire Management Plan In The Okavango Delta Ramsar Site, 2004)(Appendix 1). This concern about the widespread occurrence of wildfires provided the motivation for initiating this project to study the fire ecology of the Okavango Delta Ramsar Site and to formulate a fire management plan as part of the responsibilities of the Vegetation Resources component. The vegetation of the Okavango Delta Ramsar Site can be divided into five broad vegetation units, namely, the Permanent Swamps in the north western Panhandle region of the Delta and extending south east into the fan of the Delta; the Burkea Woodlands on either side of the Permanent Swamps; the Seasonal Swamps adjacent to the Permanent Swamps in the fan of the Delta, the Mopane Woodlands surrounding the Delta in the north east and the Acacia Woodlands in the south west (Mendelsohn & el Obeid, 2004). From historical accounts it appears that the inhabitants of the Okavango Delta used fire to burn the vegetation resources for different lifestyle practices for centuries. Tinley (1975) mentions that the Maswara River Bushmen who have inhabited the Delta since before 1750 “do considerable damage to the country by firing the flood plain grasslands, which sometimes burn for weeks”. In 1800 the Batawana community moved northward and settled in the Maun area where Stigand in 1923 noted that there were 500 dwellings at Maun and referred to the fact that they burnt the swamp and reed beds annually in preparation for ploughing. Despite fires being common and widespread in and around the Okavango Delta and as noted are an integral ecological process and historical land-use practice, the fire ecology of the Okavango Delta Ramsar Site has until recently never been intensively and scientifically investigated. A major step forward has been the five recent post-graduate research projects. These were conducted by:

• Heinl (2005) studying fire and its effects on vegetation in the Okavango Delta;



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CHAPTER 1

1. INTRODUCTION On the 4th April 1997, Botswana became a contracting party of the “Ramsar Convention” and listed the Okavango Delta, spanning an area of between 10 000 and 16 000 square kilometres, depending upon the extent of the annual flood waters, as one of the world’s largest remaining inland wetland ecosystems of international importance. The Okavango Delta Ramsar Site, which includes the Delta is situated at the northern most edge of the Kalahari Desert in north western Botswana and comprises an area of 55 374 square kilometres. The Delta is sustained by water from the Okavango River yielding between 8 - 15 thousand million cubic metres per annum from its catchment areas in Namibia and Angola (Okavango Delta Draft Framework Plan, 2005). The location and extent of the Ramsar Site are illustrated and presented in Figure 1.

Figure 1. Location of Ngamiland in Botswana and the borders of the Okavango Delta

Ramsar Site.



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• Initiation of a community based fire management program in the rural communities in the Ramsar Site;

• Fire fighting/management training courses for developing local capacity for planning and applying fire management practices and programs;

• Training in the assessment of range condition for controlled burning and the use of the Management Orientated Monitoring System for Natural Resource Management (MOMS) for the capture of range condition data as a means of developing a vegetation monitoring program for the Ramsar Site.



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burning of areas in the Seasonal Swamps and the Acacia, Burkea and Mopane Woodlands can be determined using this criterion;

� In order to prevent overgrazing it is important to ensure that the burnt area exceeds the short term forage requirements of the grazing animals that are attracted to the highly palatable and nutritious regrowth that develops after a burn i.e. burn relatively large areas at any one time. Another effective strategy is to apply a series of patch burns at regular intervals throughout the duration of the burning window during the dormant season. This has the effect of attracting the grazing animals to the newly burnt areas after the different fires thereby spreading the impact of grazing over the entire burnt area and avoiding the detrimental effects of heavy continuous grazing after the burns.

Practical Application of Controlled Burning

In the practical application of a controlled burning program the following factors must be considered:

• Weather conditions as described and assessed using the recommended Fire Danger Rating System;

• Choosing the appropriate burning procedure for the application of the controlled burn i.e. applying a block burn or a patch mosaic burn;

• The provision of adequate and appropriate firebreaks for the area being burnt;

• Having adequate equipment for both initiating and controlling the fire;

• Ensuring that the field staff are equipped with suitable protective clothing and footwear;

• Having appropriate forms of communication available to enable effective communication during the burning operation.

Application of Fire Management Plan Fire management in the Ramsar Site needs to be implemented in a coordinated manner and include all the role players within the Ramsar Site. The following aspects have been considered and described in detail for the practical application of the proposed fire management plan for the Ramsar Site:

• The appointment and establishment of a District Fire Committee with head quarters in Maun and acting as the District Fire Coordination Centre;

• Development of a fire prevention plan involving strategic and asset protection fire breaks and fire fighting capabilities;

• Recommendations on the location of suitable manned and equipped fire crews in the sub-district wards at Maun, Seronga, Shakawe and Tsau;

• Minimum fitness standards for the selection of personnel for the fire crews;

• Provision of effective communications for field crews during fire operations;

• Provision of guidelines for effective minimum requirements of equipment and personnel for commercial and private stakeholders in the Ramsar Site;

• School education program aimed at developing fire awareness and understanding fire ecology of local ecosystems;

• Advocacy and fire awareness programs for educating the local and tourist public;



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Fire Management Plan

A fire management plan has been formulated for the Ramsar Site and includes the following recommendations:

• The reasons for burning identified in the review of literature were simplified and listed as follows:

� It is ecologically permissible to burn the vegetation for the removal of moribund and/or unacceptable grass or other plant material like reeds as a means of rejuvenating the plant community;

� It is ecologically permissible to burn the vegetation to control the encroachment of undesirable plants e.g. controlling bush encroachment.

• The following fire regime in terms of type and intensity of fire and the season and frequency of burning is recommended for the Ramsar Site:

� Fires burning with the wind either as surface head fires in grassland or a combination of surface head fires and crown fires in tree and shrub vegetation must be used in controlled burning. This is because surface head fires cause least damage to the grass sward and crown fires can cause maximum damage to woody vegetation when fire is used to control bush encroachment;

� When burning to remove moribund and/or unacceptable grass material a cool fire of <1 000 kJ/s/m is recommended. This can be achieved by burning when the air temperature is <20°C and the relative humidity >50 %. When burning to control undesirable plants like encroaching bush, a hot fire of >2 000 kJ/s/m is necessary. This can be achieved when the grass fuel load is >4 000 kg/ha, the air temperature is >25°C and the relative humidity <30 %. This will cause a significant topkill of stems and branches of bush species up to a height of 3 m. In all cases the wind speed should not exceed 20 km/h;

� Controlled burning should only be applied when the grass sward is dormant. Relating this principle to the different vegetation units it is recommended that when burning to remove moribund, unpalatable grass material in either the Burkea, Acacia or Mopane Woodlands where plant growth is dependent only on rainfall, then these areas should be burnt at the end of the dormant winter season in approximately October after the first spring rains of >13 mm. When burning to control the encroachment of undesirable plants like bush encroachment, a high intensity fire is required and it is recommended that this be applied before the first spring rains in August/September when it is extremely hot and dry. In the case of burning in the Seasonal Swamps where the growth of the vegetation is generally influenced by the annual flood waters entering the Delta the ideal burning window for removing moribund and/or unpalatable grass material is during the period May to July, applying the fires when the grass sward is dormant before the flood waters start rising. If it should be necessary to reduce the growth of trees and shrubs in the Seasonal Swamps then burning must be applied later in the winter during August/September when it is extremely hot and dry thereby ensuring high intensity fires necessary to control encroaching trees and shrubs;

� When burning to remove moribund and/or unacceptable grass material the frequency of burning will depend upon the accumulation rate of excess grass litter. Field experience indicates that burning is necessary for this reason when the grass fuel load exceeds 4 000 kg/ha and therefore the frequency of



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• The development of a simple and practical vegetation map of the Ramsar Site based on the five vegetation units comprising the Acacia, Burkea and Mopane Woodlands and the Permanent and Seasonal Swamps that have proved to be a very practical classification of the vegetation for management purposes;

• The initiation of a fire research program to determine quantitatively the effects of type and intensity and season and frequency of burning on the botanical composition, productivity, sustainability and biodiversity of the different dominant plant communities occurring in the different vegetation units identified in the fire management plan for the Ramsar Site;

• The development of a simplified technique for assessing the condition of the vegetation, particularly the grass sward, using key grass species;

• The testing of the calibration for the disc pasture meter for estimating grass fuel loads in the different vegetation units in the Ramsar Site;

• Conduct a comprehensive assessment of the condition of the grass sward and the tree and shrub vegetation in all the different vegetation units in the Ramsar Site;

• Conduct detailed autecological studies on the key grass, non-grass herbaceous species and tree and shrub species in the Ramsar Site commencing with Cyperus papyrus in the Permanent Swamps;

• Investigate whether a symbiotic relationship exists between Cyperus papyrus, Phragmites, mauritianus, Miscanthus junceus, Echinochloa stagnina and Vossia cuspidata and mycorrhiza and the role that mycorrhiza may play in the uptake of nutrients, particularly phosphorous in the Permanent Swamps;

• Investigate the impact of frequency and season of burning of Cyperus papyrus on aggradation, deposition of bed-load sediments and channel flow in the Okavango Delta as these functions are vital to the dynamics, functioning and survival of the Okavango Delta;

• Investigate the flammability of Cyperus papyrus to test the hypothesis that this species contains volatile substances that enhances its flammability and therefore its threat as fire hazard in the Permanent Swamps in the Ramsar Site;

• Investigate the effect of frequency of burning on water quality as related to fish die-off to test the hypothesis that emissions and ash from fires are responsible for the die-off of fish populations after fires in the Delta;

• Investigate the role of fire in preventing channel blockages by testing the hypothesis that reductions in frequency of burning and complete fire suppression are agents of channel blockages in the Delta;

• Determine the effect of type and intensity and season and frequency on reptile populations, particularly pythons, in the Permanent Swamps as several stakeholders have enquired about these fauna in the Delta;

• Recommend that climatic and weather data be made more available and readily accessible to the general public in the Ramsar Site in order facilitate the formulation of an effective fire management and fire prevention program for the Ramsar Site;

• Recommended that the number of weather stations in the Ramsar Site be significantly expanded to provide a more comprehensive coverage of the climatic conditions in the region.



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� Many of the firebreaks were planned not taking local circumstances and weather into consideration. For instance, some fire breaks were constructed parallel to the prevailing easterly winds and would therefore not prevent a wildfire from spreading in a westerly direction. Aerial surveys also showed that existing strategic fire break systems have not been maintained and unless attended to immediately would not be effective in controlling the spread of wildfires during this fire season;

� Greater use could be made of natural barriers in the landscape as firebreaks and with limited use of strategic burning potential buffer zones could be created with minimal impact on the sensitive environment in many areas of the Ramsar Site.

• The Herbage Preservation Act promulgated in 1977 is the legal framework administering the management of fire in Botswana. A detailed study of this legislation indicates that certain changes are needed to enable the effective management of fires both in Botswana and in the Okavango Delta Ramsar Site viz.: � The Act requires additions to its existing content to assist the State

Departments and land users in the implementation of the recommendations that are proposed in the fire management plan. These include a system to evaluate the fuels before burning to determine the necessity to burn;

� The implementation of a Fire Danger Rating system that would create a safer environment to carry out controlled burning and provide the predictive means for reducing the threat of fires to humans, infrastructure and the environment as a whole;

� The establishment of a District Fire Committee for which membership must be made mandatory for all representatives of land users within the Ramsar Site and must include all stakeholders, both state and private;

� The establishment of sub-district wards at Maun, Seronga, Shakawe and Tsau under the control of the District Fire Committee based in Maun;

� The de-centralization of the existing Government fire crews to the sub-district wards to allow for crews to react to the initial attack on wildfires on government and community land.;

� The establishment of 11-person fire crews stationed at the sub-district wards where they will be closer to assist with extended attack on fires and be available to assist with burning existing firebreaks and perform any controlled burning required by the communities and/or other stakeholders;

� The decentralization of the issuing of burning permits to offices in the sub-district wards;

� The existing burning permits must include a burning plan outlining reason for burning, range condition, resources and manpower and weather conditions and fire danger index for the day of the burn;

Research Requirements & Scientific Services

An assessment of current knowledge on the fire ecology of the Ramsar Site led to the following recommendations on immediate and long term applied and basic research requirements and the development of scientific services necessary for implementing the proposed fire management plan:



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rather by the excessive fuel loads that accumulate rapidly in the dense stands of papyrus;

• The technique used to assess the condition of the grass sward in the Acacia, Burkea and Mopane Woodlands and the Seasonal Swamps proved to be very successful in indicating whether the grass sward in these vegetation units needed to be considered for burning or not. The ecological criteria used in this technique for assessing the condition of the grass sward relative to fire proved to be very effective and comprised:

� Burning is ecologically acceptable if the grass sward is in a climax and/or sub-climax stage dominated by Decreaser and/or Increaser I grass species as a means of maintaining the potential of the grass sward to produce grazing for both domestic livestock and wildlife. Conversely burning should not be applied when the grass sward is in a pioneer condition dominated by Increaser II grass species in order to allow it to develop to a more productive stage dominated by Decreaser grass species;

� Burning is ecologically acceptable if the grass sward is in a moribund/ and or unpalatable condition as a means of restoring the vigour of the grass sward and allow new nutritious regrowth to occur. Field experience indicates that when the standing crop of grass >4 000 kg/ha in African grasslands and savannas then the grass sward has become moribund and/or unacceptable to grazing animals and needs to be defoliated by burning or some other means.

Current Fire Control Strategies

An assessment of the current strategy to control fire in the Ramsar Site provided the following information:

• Currently all fire fighting equipment and staff are centralized in Maun and an inspection of these resources showed that there were 16 fire fighting units referred to as “slip-on’s” or “bakkie sakkies” and these were assessed to be adequate for the task of suppressing wildfires in the Ramsar Site. However, a significant number of the units were not in working order and available for instant use if required. Also the units stored at the offices of the Department of Forestry and Range Resources were not suitably housed under cover and were exposed to the elements of the weather and were showing signs of deterioration due to the effects of rain, high day temperatures and harsh sunlight;

• An assessment of the number and condition of the knapsack sprayers showed that there were an inadequate amount for the task at hand and were generally in very poor non-working condition being stored in the open between two buildings at the departmental office. There are approximately121 fire beaters but these need to be properly stored and maintained;

• The assessment revealed that the staff involved in fire suppression were inadequately trained and not equipped with suitable clothing and footwear for fighting fires;

• It was concluded that the decentralization of responsibilities, staff and equipment is a pre-requisite for the development of an effective fire suppression capability in the Department of Forestry and Range Resources;

• An assessment of the existing fire breaks in around the Ramsar Site led to the following conclusions:



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� to improve access to the Permanent and Seasonal Swamps for fishing and setting of nets;

� to improve the quality of papyrus for weaving of mats by removing old dead shoots and stimulating new growth;

� to improve access in the Seasonal Swamps for harvesting bulbs of water lilies;

� to clear land in preparation for establishment of crops;

• The main season of burning for both the dryland Acacia, Burkea and Mopane Woodlands and the Seasonal and Permanent Swamps is the dry period of the year approximately between May and October. However, the swamps tend to burn earlier peaking in June immediately before the arrival of the floodwaters while the dryland woodland areas burn later at the end of winter before the start of the rainy season in October;

• The annual frequency of fires varies significantly in response to a highly variable rainfall and in the case of the swamps to variations in the inflow of water into the Okavango River. The most frequently burnt vegetation units are the Permanent Swamps and Burkea Woodlands with the Seasonal Swamps having significant numbers of fires but occurring less frequently. The Acacia and Mopane Woodlands are very infrequently burnt because of their low grass productivity;

• The effects of fires differed between the flooded swamp areas and the dryland areas; � In the swamp areas fires have little effect on the vegetation because the

growing points of the plants are either inundated by water or are growing in moist soil.

� In the dryland vegetation units the general response of the vegetation to fire is similar to the savannas elsewhere in southern Africa where grassland and open savanna are promoted by frequent burning and vice versa.

Assessment of Condition Of Vegetation

The assessment of the condition of the vegetation in the different vegetation units led to the following conclusions:

• The Seasonal Swamps and the burnt area north east of Tsodilo in the Burkea Woodlands had the highest potential for producing grass fuel that could initiate and sustain wildfires compared to the other vegetation units. This is because the grass sward in these areas was dominated by perennial grass species with an inherently higher genetic potential to produce large quantities of grass fuel compared to the grass sward in the other vegetation units which was dominated by annual grass species with a low potential;

• The Permanent Swamps comprising extensive plant communities dominated by Cyperus papyrus (papyrus) and Phragmites spp. (reeds) had extremely high fuel loads capable of generating high intensity fires. These plant species have an extremely high growth rate and are highly resistant to burning because their growing points are either inundated by water or are growing in moist soil. The papyrus was found not to contain highly flammable volatile and it was concluded that the extremely high intensity fires associated with this plant community were caused



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“Panhandle”. The river brings water from the central Angolan highlands, where rainfall is three times higher than the 450 – 500 mm/year in the Delta region and the average annual inflow at the border with Namibia at Mohembo is 10 000 million m3. Downstream from Panhandle the Okavango River spills out over a large area as it divides into a number of distributary channels, forming a vast alluvial fan. Climate The Okavango Basin is characterized throughout by warm or hot conditions during most of the year and for much of every day. Annual temperatures throughout the area average 20oC, increasing by two or three degrees from north to south as a result of the higher solar radiation in the southern areas. When there are no clouds, temperatures can peak as high as 40oC. The winds in the Ramsar Site blow predominantly from the east with strong winds in excess of 20 km/h occurring 35 % of the time which can have a very significant effect on the potential for fires in the Ramsar Sites particularly during the dry late winter period. Land Use

The major forms of land use in the Ramsar Site are communal areas used for pastoral and arable agriculture (49%), wildlife management areas involving tourism (42%) and the Moremi Game Reserve involving nature conservation and tourism (9%). Review Of Literature A review of the available literature on the fire ecology of the Ramsar Site, information obtained via interviews with different stakeholders, an analysis of the occurrence of fires recorded by satellite and an assessment of the condition of the vegetation in the different vegetation units led to the following conclusions regarding the occurrence and effects of fires in the study area:

• Fire is recognized both scientifically and politically as an important ecological factor and a traditional land-use practice;

• The overwhelming majority of fires are anthropogenic in origin being associated with the different human activities that include livestock farming, wildlife management, hunting, fishing, tourism, harvesting plant materials for household needs, preparing croplands and preparing firebreaks for safeguarding property;

• The ecologically acceptable reasons given for using fire as a management practice are:

� to improve the quality of grazing for domestic livestock and wildlife; � to attract wildlife to green grazing for improved viewing by tourists; � to attract wildlife to green grazing for improved hunting; � to improve the quality of thatch grass and reeds by removing plant debris after

harvesting; � to construct burnt firebreaks to safeguard property; � to increase fish populations in the Permanent and Seasonal Swamps by

stimulating new shoots palatable to fish and promote better nesting conditions for fish when the flood arrives;



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• Banda (2004) researched the influence of burning on micro-organisms along the Boro route in the Okavango Delta.

While all these studies are highly commendable and significant scientific contributions to describing and understanding the fire ecology of the Okavango Delta they were are all short-term investigations that could not fully describe the long-term effects of burning on the vegetation in the different vegetation types in the Delta. Objectives

The overall objective of the project was to gain an understanding of the impact of fire in the Delta and based on literature reviews, interviews with stakeholders and an assessment of the condition of the vegetation, develop a fire management plan for the Okavango Delta Ramsar Site in order to ensure sustainable use and management of the vegetation in the Delta and to control injudicious burning and wildfires occurring in this unique African wetland ecosystem. The specific objectives of the project were to:

• Determine the basic causes of fire in the Delta;

• Determine the effects of fires on the major landscapes/vegetation types and associated fauna;

• Develop simple and practical quantitative ecological criteria that can be used to differentiate between areas that can be considered for controlled burning and areas where fire should be excluded to safeguard the productivity, sustainability and biodiversity of the ecosystem.

• Produce a fire management plan that: � States the ecologically permissible and non-permissible reasons for burning; � Describes the fire regime in terms of type and intensity of fire and season and

frequency of burning recommended for controlled burning; � Describes the practical procedures to be followed and equipment to be used

for the successful and safe application of controlled burning; � Identifies aspects of the fire regime and its effects on the ecosystem that

require further research;

• Addresses the requirements of the Herbage Preservation Act relating to controlled burning;

• Involve Botswana Government staff and other relevant stakeholders in the development of the fire management plan.

Study Site The Okavango Delta Ramsar Site is characterized by Kalahari sandveld that covers much of central and southern Africa and is flat to undulating with an overlay of aeolian Kalahari sandbeds that can reach a depth of up to 300 meters. The present day Okavango Delta is an alluvial fan, its shape governed by tectonic faults. The distal end of the Delta is controlled by the two northeast-southwest trending faults, the Kunyere and Thamalakane faults, with the down-throw to the northwest. The proximal end of the Delta is limited by a third parallel fault, the Gumare/Chobe fault with the down-throw to the southeast. The pattern of these faults delineates a graben structure, filled with alluvial sediments. The Okavango River with its catchment in Angola, flows across the Caprivi Strip in Namibia and enters Botswana at the town of Mohembo in the north-western region of Botswana. Before it fans out into the Delta the rivers follows a narrow channel, 10 – 15km wide, known as the



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EXECUTIVE SUMMARY

On the 4th April 1997, Botswana became a contracting party of the “Ramsar Convention” and listed the Okavango Delta, spanning an area of between 10 000 and 16 000 square kilometres, as one of the world’s largest remaining inland wetland ecosystems of international importance. The Okavango Delta Ramsar Site, which includes the Delta is situated at the northern most edge of the Kalahari Desert in north western Botswana and comprises an area of 55 374 square kilometres. The Delta is sustained by water from the Okavango River yielding between 8 - 15 thousand million cubic metres per annum from its catchment areas in Namibia and Angola. Arising from this contractual commitment and in order to ensure the Okavango Delta’s conservation and wise use, the Okavango Delta Management Plan (ODMP) project proposal was drawn up in 2002. An important components listed in the ODMP report was that of Vegetation Resources and its management is the responsibility of the Department of Crop Production (DCP) in the Ministry of Agriculture and the Department of Forestry and Range Resources in the Ministry of Environment, Wildlife and Tourism. This component has the responsibility “to ensure sustainable management of the Okavango Delta vegetation initiated and supported by providing accurate data and assisting in resolving vegetation management conflicts” This includes considering the ecology and use of fire in the Okavango Delta Ramsar Site where generally wild fires are perceived to be an increasing problem in terms of their frequency, severity and uncontrolled nature. This concern about the widespread occurrence of wildfires provided the motivation for initiating this project to study the fire ecology of the Okavango Delta Ramsar Site and to formulate a fire management plan as part of the responsibilities of the Vegetation Resources component. The vegetation of the Okavango Delta Ramsar Site can be divided into five broad vegetation units, namely, the Permanent Swamps in the north western Panhandle region of the Delta and extending south east into the fan of the Delta; the Burkea Woodlands on either side of the Permanent Swamps; the Seasonal Swamps adjacent to the Permanent Swamps in the distal portion of the Delta, the Mopane Woodlands surrounding the Delta in the north east and the Acacia Woodlands in the south west. From historical accounts it appears that the inhabitants of the Okavango Delta used fire to burn the vegetation resources for different lifestyle practices for centuries. Despite fires being common and widespread in and around the Okavango Delta and as noted are an integral ecological process and historical land-use practice, the fire ecology of the Okavango Delta Ramsar Site has until recently never been intensively and scientifically investigated. A major step forward has been five recent post-graduate research projects investigating different aspects of the fire ecology in the Ramsar Site, viz.:

• Heinl (2005) studied fire and its effects on vegetation in the Okavango Delta;

• Tacheba (2002) determined the extent and season during which fires occurred during September 2000 and 2001 in portions of the Permanent and Seasonal Swamps and areas of Mopane and Acacia Woodlands;

• Cassidy (2003) investigated the livelihoods and spatial dimensions of anthropogenic burning in the Okavango Panhandle;

• Tlotlego (2004) investigated the effects of fire threatening the production of thatching grass in the Panhandle region of the Delta;



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Mac and Brenda McKenzie deserve special mention for all the assistance, advice, friendship and emergency email service when all else failed!

To those stakeholders we did not get the opportunity to interview or consult please accept our apologies – it in no way negates the value of your information but it was purely due to time constraints that the opportunity did not materialise.

To our fellow EnviroNet consultants – thank you for the camaraderie, hard work and team spirit. To Anya Hofman from the GTZ office in Gaborone, your assistance and advice was sincerely appreciated. Finally, special thanks are due to the Lowveld Fire Association in Nelspruit, South Africa for the provision of the Cessna 206 to facilitate the surveys of the Delta and to Egmund van Dyk, a truly accomplished pilot and friend.

Winston and Lynne Trollope



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ACKNOWLEDGEMENTS

The preparation of the Fire Management Plan for the Okavango Delta Ramsar Site has been both an enriching, exciting and challenging experience and the EnviroNet Consultants wish to express their most sincere appreciation and thank all their colleagues and new found friends who have facilitated and contributed in many ways to this assignment. In particular we wish to express our gratitude to Dr Comfort Molosiwa, Project Co-ordinator for the Okavango Delta Management Plan, for his valuable guidance on the ODMP requirements for the structure and format for the presentation of reports, for his patience and invaluable assistance in many aspects of the project and the finesse with which he accomplishes many things. We wish him well in the preparation of the overall Management Plan for the Okavango Delta Ramsar Site. We thank Ms Portia Segomelo for her dedication, leadership and introduction to the ODMP at the commencement of the project. Mr Sekgowa Motsumi, the ODMP Information and Communications Officer always meticulously read the reports and offered constructive comments which were most valuable, and the staff at the ODMP we thank for the warm welcome to Maun and their courteous co-operation and assistance at all times.

We express our appreciation to Mr Raymond Kwerepe the immediate past Director and the new Director Dr K Molopang of the Department of Forestry and Range Resources in Gaborone for facilitating the project and providing administrative support. Mr Boikago Maswabi and his staff, especially Malaakgosi Mafhoko and Mmika Letileng, at the Department of Forestry and Range Resources in Maun, were always enthusiastic, co-operative and great people to work with. Our field trips engendered a friendship that will not easily be forgotten and we truly appreciated their willingness and enthusiasm to conduct surveys during public holidays and over weekends and their eagerness to adopt new technology for assessing range condition and their interest in the Fire Danger Rating System.

Invaluable assistance was also unstintingly offered by the staff of the Harry Oppenheimer Okavango Research Institute, University of Botswana, in Maun and we would like to thank in particular the Director, Dr L Ramberg, Dr Casper Bonyongo, Dr Cornelis van der Post, Mike and Francis Murray-Hudson, Dr Susan Ringrose, Connie Masalila, Hannelore Bendsen, Marion Morrison, Herbert and staff of the HOORC Library. We express our grateful thanks to Mike Murray-Hudson, Mosie Innele and Thebe for their patience in stopping on innumerable occasions during a visit by boat to the HOORC field station and for sharing their insights on the Delta with us. Their excellent boating skills made our investigation of the seasonal swamps a fascinating and truly enlightening experience. Dr Casper Bonyongo also provided most valuable insights into the functioning of the Okavango ecosystem, assisted with numerous articles and books on the Delta and was always willing to discuss and comment on many topics and ideas related to the project.

To the many other stakeholders from the commercial sector, government departments, NGO’s, communities and private individuals, who shared their knowledge and enlightened us on this fascinating and wonderful ecosystem, we thank you for your time and information. Special thanks go to Map Ives, Mark Kyriacou, Lloyd Wilmot, Alan Schmidt, Patrick Pentstone, Pete Hancock, Debbie Gibson, Batusi Letlhare, Simon Allen, Lee Ouzman, Willie and Anne Phillips, Jan, Eileen and Donovan Drotsky and Piet Scheepers.



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List of Appendices Appendix 1 Terms of Reference ………………………… 166 Appendix 2. Rainfall data for Maun and Shakawe ………………………… 174 Appendix 3. Details of responses from interviews with stakeholders ……… 179 Appendix 4. Proposed amendments to the Herbage Preservation Act …… 193 Appendix 5. Grass Fuel and Forage Factors ……………………….. 202 Appendix 6. Botanical Survey Data Digital copy only

ABBREVIATIONS AND ACRONYMS

ODMP Okavango Delta Management Plan DFRR Department of Forestry and Range Resources ARB Agricultural Resources Board DWNP Department of Wildlife and National Parks DCP Department of Crop Production HOORC Harry Oppenheimer Okavango Research Center ITCZ Inter-tropical Convergence Zone PRA Participatory Rural Appraisal CBPP Contagious Bovine Pleural Pneumonia FDI Fire Danger Index PPC Personal Protective Clothing



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List of Tables Table 1. The monthly mean, maximum and minimum air temperatures for Maun and Shakawe in the ODRS for the period 1967 – 1998 .……………….… 26 Table 2. The monthly mean, maximum and minimum relative humidity for Maun and Shakawe in the ODRS for the period 1967 – 1998 .……….………… 27 Table 3. Annual percentage frequency of wind direction recorded at Maun (1968 – 1978) and Shakawe (1966 – 1969) in the ODRS .……….………… 27 Table 4. The areas and proportion of the major vegetation units in the ODRS and their relationships with the original vegetation types identified and classified by Jellema, Ringrose and Matheson at HOORC in Maun …….…… 29 Table 5. Existing broad land use categories in the ODRS ……………...…… 39 Table 6. Technique for assessing the grazing potential of the grass sward and the necessity for controlled burning in the Acacia, Burkea and Mopane Woodlands and the Seasonal Swamps in the ODRS ………..... 70 Table 7. Technique for assessing the potential of the grass sward to produce thatch material and the necessity for controlled burning in the ODRS ..…..… 74 Table 8. The effects of basal cover (point to tuft distance – cm), grass standing crop (kg/ha) and the proportion of annual grasses and non-grass species (%) on the resistance to accelerated soil erosion in the Seasonal Swamps and Acacia, Burkea and Mopane Woodlands in the ODRS ………... 87 Table 9. The mean canopy cover, height and prominent tree and shrub species recorded in the Seasonal Swamps and Acacia, Burkea and Mopane Woodlands in the ODRS …………………… 88 Table 10. A comparison of the botanical composition (%), density (plants/hectare), phytomass (tree equivalents per hectare) of an unburnt area and a frequently burnt area in the Tsodilo region of the Burkea Woodlands in the north western region of the ODRS …………………………..… 90 Table 11. The impact of frequent high intensity fires on the mortality of large trees >10m in height in the Tsodilo region of the Burkea Woodlands in the north western region of the ODRS …………………………….. 91 Table 12. Fire Danger Rating System for controlled burning and fire suppression in African Grasslands and Savannas …………………………….. 105 Table 13. Burning Permit Plan …………………………….. 107 Table 14. Calibration for the Disc Pasture Meter developed in the Kruger National Park in South Africa and recommended for use in estimating grass fuel loads in African grasslands and savannas for management purposes (Trollope & Potgieter, 1986) ………………………….….. 116 Table 15. Fire Danger Rating System using Fire Danger Indices as a means for selecting suitable burning conditions for controlled burning ………………….… 125



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Figure 26. Potential of the vegetation to produce grass fuel to initiate and sustain fires, and forage for domestic livestock and wildlife in the Seasonal Swamps and Acacia, Burkea and Mopane Woodlands in the ODRS, expressed as fuel and forage scores ………………..………….. 83 Figure 27. Mean frequency of Decreaser, Increaser I and Increaser II grass species in the seasonal swamps and Acacia, Burkea and Mopane Woodlands in the ODRS, expressed as fuel and forage scores ………… 84 Figure 28. The mean grass fuel loads expressed in kilograms per hectare recorded in the seasonal swamps and Acacia, Burkea and Mopane Woodlands in the ODRS ………………….………… 86 Figure 29. On the left is the more dense woody vegetation in the unburnt area at Tsodilo and on the right is the more open vegetation in the burnt area 8km north east of Tsodilo ………………….………… 92 Figure 30. A view of the significant mortality of the large trees >10m in the burnt area north east of Tsodilo and the negative impact of bark stripping by elephant and fire on a large Pterocarpus angolensis (Kiaat) tree in the burnt area ………………….………… 93 Figure 31. Narrow water channels lined with dense stands of papyrus (Cyperus papyrus) four to five metres in height dissecting the permanent swamps in the Panhandle region of the Okavango Delta ………………….. 93 Figure 32. On the left a view of the papyrus community near Seronga that had regrown after 3 months to a height of approximately 3m after a fire in January, 2006, on the right a mature stand of unburnt papyrus located opposite the burnt area showing the accumulation of dead shoots that grow, mature and die after 90 days ………………….. 94 Figure33. Views of the high intensity fire that burnt the papyrus swamps opposite Drotskys Cabins at Shakawe on 19

th November, 2005 ………… 95

Figure 34. From left to right: the high flammability of dry papyrus umbels burning intensely in contrast to the green, live papyrus umbel and finally the successful but less intense combustion of a combination of dry and green, live papyrus umbels ………………….. 96

Figure 35. Proposed decentralization of the fire related responsibilities of the District Fire Committee in Maun to Sub-District Wards in Seronga, Shakawe, Tsau and Maun as provided for under the proposed Amendments to the Herbage Preservation Act ………………….. 102 Figure 36. The infrastructure showing delegation of responsibilities for issuing burning permits for controlled burning by the District Fire Committee ………. 103 Figure 37. The Disc Pasture Meter developed by Bransby and Tainton (1977) used to estimate the standing crop of herbaceous plant material in a grass sward …………………. 116 Figure 38. The procedure for using a perimeter ignition to apply a block burn ………… 127 Figure 39. Illustration of head, back and flank fires resulting from applying a Point ignition ………………….. 128 Figure 40. The procedure for using a point ignition for applying a patch mosaic burn …. 132 Figure 41. Procedure for constructing dry and wet line fire breaks ………………….. 131 Figure 42. The Botha Fire-Box comprising four sheets of corrugated iron fitted with four wooden handles ………………….. 133 Figure 43. A drip torch used for laying fire lines ………………….. 134



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List of Figures Figure 1. The Okavango Delta Ramsar Site (ODRS) ….………………………… 1 Figure 2. The process of consultation undertaken to develop a Fire Management Plan for the ODRS ………............................. 6 Figure 3. Location of the Okavango Delta Ramsar Site in Ngamiland Province in north western Botswana ………………….………… 18 Figure 4. Mean monthly and annual rainfall recorded at Maun and Shakawe in the ODRS ………………….………… 22 Figure 5. The previous twelve months rainfall recorded at Maun for the period 2000 – 2006 illustrates the highly variable nature of the seasonal and annual rainfall in the ODRS ……………………………. 23 Figure 6. Mean monthly inflow of water into the Okavango River from January to July recorded at Mohembo for the period 1984 – 2006. Data expressed in cubic meters of water per second i.e. cusecs ………… 24 Figure 7. Total annual inflow of water during January to July in the Okavango River recorded at Mohembo in the ODRS for the period 1984 – 2005 ……………………….…… 25 Figure 8. Location of Acacia, Burkea and Mopane Woodlands and Seasonal and Permanent Swamps in the ODRS ……………………………. 30 Figure 9. A typical example of Burkea Woodland in the ODRS ………………….. 31 Figure 10. Acacia Woodland in the south western region of the ODRS ………………….. 32 Figure11. A fine stand of Mopane Woodland in the north eastern region of the ODRS.. 33 Figure 12. Cyperus papyrus in the Permanent Swamps in the ODRS …………………. 34 Figure 13. The successional plant communities in the channels of the Permanent Swamps – Vossia cuspidata flanked by Cyperus papyrus With tall Miscanthus junceus in the background …………………………… 37 Figure 14. Hyphaene petersiana on the terraces in the Seasonal Swamps of the ODRS 38 Figure15. The interrelationships between the causes of fires in the ODRS and the activities related to different systems of land use that may result in the development of wildfires ……………………………. 55 Figure 16. The total number and distribution of fires in the different vegetation units recorded in the ODRS during the year 2000 …………………………… 56 Figure 17. The total number and distribution of fires in the different vegetation units recorded in the ODRS during the year 2001 ……………………………. 58 Figure 18. The total number and distribution of fires in the different vegetation units recorded in the ODRS during the year 2002 ……………………………. 60 Figure 19. The total number and distribution of fires in the different vegetation units recorded in the ODRS during the year 2003 ……………………………. 62 Figure 20. The total number and distribution of fires in the different vegetation units recorded in the ODRS during the year 2004 ……………………………. 64 Figure 21. Total number and distribution of fires in the different vegetation units recorded in the ODRS during the year 2005 ……………………………. 66 Figure 22. Total number of fires recorded per year by satellite and the mean annual rainfall for Maun and Shakawe in the ODRS for the period 2000 – 2005 ……………………………. 67 Figure 23. Mean number of fires recorded per month by satellite in the ODRS for the period 2000 – 2005 ……………………………. 68 Figure 24. Total number of fires recorded per vegetation unit by satellite in the ODRS for the period 2000 – 2005 ……………………………. 69 Figure 25. On the left a typical stand of papyrus (Cyperus papyrus) growing in the Panhandle region of the ODRS with a fringe of floating Vossia cuspidata grass at the base of the tall growing papyrus community. On the right a well developed reed community of Phragmites australis growing in the Permanent Swamps of the Boro River in the fan region of the Okavango Delta ……………………………. 81



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6.2.4.2.3 Communications ………………………………. 139 6.3 Fire management plan for the ODRS ………………………………. 140

6.3.1 District Fire Committee ………………………………. 140 6.3.2 District Fire Coordination Centre ………………………………. 140 6.3.3 Fire prevention plan ………………………………. 141

6.3.3.1 Strategic fire breaks ………………………………. 141 6.3.3.2 Asset protection fire breaks ………………………. 141

6.3.4 Fire fighting capabilities ………………………………. 142 6.3.4.1 Coordinating fire fighting ………………………………. 142

6.3.4.1.1 Initial attack (Rapid Response) ………………. 144 6.3.4.1.2 Extended attack ………………………………. 144 6.3.4.1.3 Aerial coordination ………………………………. 144

6.3.4.2 Government Sub-District Ward fire crews …………… 144 6.3.4.3 Communications ……………………………….. 146

6.3.5 Guidelines for minimum requirements for commercial/ private stakeholders ……………………………….. 147

6.3.5.1 Per single tourist lodge/tented camp site …………….. 147 6.3.5.2 Per prescribed burning operation ………………. 147

6.4 Advocacy and Fire Awareness Education ………………………. 147 6.4.1 Advocacy ………………………………. 148 6.4.2 Awareness campaigns and programs ………………………. 149

6.4.2.1 Tourism sector ………………………………. 149 6.4.2.2 Community-based fire management ………………. 149 6.4.2.3 School education program ………………………. 150

6.5 Recommendations for Future Training and Capacity Building for Future Fire Management ……………………………….. 151

6.5.1 “On the Job” training of staff ……………………………….. 151 6.5.2 Future training ……………………………….. 152 6.5.2.1 Fire fighting/management training ……………….. 152

6.5.2.2 Training in monitoring ……………………………….. 153 6.6 General Discussion and Conclusion ……………………………….. 153

REFERENCES ……………………………….. 157



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5.3.2.1 Current situation ………………………………. 100 5.3.2.2 Proposed changes to the Herbage Preservation Act . 100

5.3.2.2.1 Establishment of District Fire Committees and Sub-District Wards ………………………. 100

5.3.2.2.2 Delegation of responsibilities for issuing Burning Permits ………………………………. 102 5.3.2.2.3 Fire Danger Rating System ………………. 103 5.3.2.2.4 Prohibition on burning vegetation ………………. 106 5.3.2.2.5 Duties to extinguish fires ………………………. 106 5.3.2.2.6 Readiness for fighting fires ………………………. 106 5.3.2.2.7 Burning permit ……………………………… 106

5.3.3 Proposed amended Herbage Preservation Act ……………… 108 5.4 Identification of Deficiencies in Current Knowledge on Fire Ecology of the Ramsar Site ………………………………. 108

5.4.1 Applied research ………………………………. 108 5.4.2. Basic research ………………………………. 110 5.4.3 Scientific services ………………………………. 112

CHAPTER 6 6. RECOMMENDED FIRE MANAGEMENT PLAN FOR THE ODRS .……. 113

6.1 Introduction ………………………………. 113 6.1.2 Reasons for burning ………………………………. 113 6.1.3 Ecological criteria for prescribed burns ………………………. 115 6.1.4 Fire regime ………………………………. 118

6.1.4.1 Type of fire ……………………………. 118 6.4.1.2 Fire intensity ………………………………. 119 6.4.1.3 Season of burning ………………………………. 119 6.4.1.4 Frequency of burning ………………………………. 120 6.1.4.5 Post-burn range management ………………………. 120

6.2 Application of a Controlled Burning Program ………………………. 120 6.2.1 Fire Danger Index for controlled burning ………………………. 120

6.2.1.1 Practical example of the calculation of the Fire Danger Index ………………………………. 126 6.2.2.2 Vegetation monitoring ………………………………. 126

6.2.2 Burning procedure ………………………………. 127 6.2.1.1 Block burns ………………………………. 127 6.2.2.2 Patch mosaic burns ………………………………. 128

6.2.3 Fire breaks ………………………………. 131 6.2.31. Dry and wet line fire breaks ………………………. 131 6.2.3.2 Cut-line fire breaks ………………………………. 132 6.2.3.3 Tracer line fire breaks ………………………………. 132 6.2.3.4 The Botha Fire-Box ………………………………. 133 6.2.3.5 Width of fire breaks ………………………………. 133

6.2.4 Burning equipment ………………………………. 134 6.2.4.1 Equipment for initiating a fire ………………………. 134 6.2.4.2 Equipment for controlling and fighting fires ………. 135

6.2.4.2.1 Persona protective clothing (PPC) ………. 135 6.2.4.2.2 Fire fighting tools ………………………………. 137



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4.3.3 Annual flood – Okavango River ………………………………. 24 4.3.4 Air temperature and relative humidity ………………………. 25 4.3.5 Wind ………………………………………. 27

4.4 Vegetation ………………………………………. 28 4.4.1 Woodlands ………………………………………. 30 4.4.2 Permanent and Seasonal swamps ………………………. 32 4.5 Land Use ………………………………………. 39

4.5.1 Communal areas, settlements, arable and pastoral agriculture ………………………………. 40

4.5.1.1 Livestock ………………………………. 40 4.5.1.2 Crop farming ………………………………. 41 4.5.1.3 Fishing ………………………………. 41 4.5.1.4 Hunting ………………………………. 42 4.5.1.5 Harvesting reeds, thatching grass, papyrus And veld products ………………………………. 42

4.5.2 Wildlife management areas ………………………………. 43 4.5.2.1 Tourism ………………………………. 43

4.5.2. Game reserves ………………………………. 43

CHAPTER 5 5. FIRE ECOLOGY OF THE OKAVANGO DELTA RAMSAR SITE (ODRS) 45

5.1 Collection, Assimilation, Analysis and Evaluation of Information Pertinent to the Fire Ecology of the ODRS ………. 45

5.1.1 Review of literature on the fire ecology of the ODRS ………. 45 5.1.1.1 Ignition sources of fire ………………………………. 46 5.1.1.2 Reasons for burning ………………………………. 46 5.1.1.3 Season of burning ………………………………. 46 5.1.1.4 Frequency of burning ………………………………. 47 5.1.1.5 Type and intensity of fire ………………………………. 47 5.1.1.6 Effects of fire ………………………………. 48

5.1.2 Interviews related to the fire ecology of the ODRS ………. 50 5.1.3 Satellite data related to the fire ecology of the ODRS ………. 55 5.1.3.1 Annual occurrence and distribution of fires ………. 55

5.2 Assessment of the Condition of the Vegetation Relative to Burning in the Major Vegetation Types in the ODRS ………. 70

5.2.1 Introduction ………………………………………. 70 5.2.2 Procedure for assessing range condition ………………. 70

5.2.2.1 Grass sward ………………………………………. 70 5.2.2.2 Tree and shrub vegetation ………………………. 79 5.2.2.3 Permanent swamps ………………………………. 81

5.2.3 Results ………………………………. 82 5.2.3.1 Grass sward ………………………………. 82 5.2.3.2 Tree and shrub vegetation ………………………. 88 5.2.3.3 Permanent swamps ………………………………. 93 5.2.3.4 Discussion and conclusion ………………………. 98

5.3 Assessment of Current Strategies to Control Fire in the ODRS …… 99 5.3.1 Fire suppression ………………………………. 99 5.3.2 Herbage Preservation Act ………………………………. 100



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TABLE OF CONTENTS

Page LIST OF FIGURES ……………………………………….. vi LIST OF TABLES ……………………………………….. viii APPENDICES ……………………………………….. ix ABBREVIATIONS AND ACRONYMS ………………………………………. ix ACKNOWLEDGEMENTS ………………………………………. x EXECUTIVE SUMMARY ………………………………………. xii CHAPTER 1 ………………………………………. 1 1. INTRODUCTION ………………………………………. 1

CHAPTER 2 ………………………………………. 5 2. OBJECTIVES OF THE PROJECT ………………………………………. 5

CHAPTER 3 ………………………………………. 7 3. OVERVIEW OF FIRE ECOLOGY OF AFRICAN

GRASSLANDS AND SAVANNAS ………………………………………. 7 3.1 Fire Behaviour ………………………………………. 7

3.1.1 Fire intensity ………………………………………. 7 3.1.2 Factors influencing fire intensity ………………………………. 7 3.1.2.1 Fuel load ……………………………………….. 8 3.1.2.2 Fuel moisture ……………………………………… 8 3.1.2.3 Air temperature ….…………………………………... 8 3.1.2.4 Relative humidity ………………………………………. 8 3.1.2.5 Wind ……………….……………………… 9 3.1.2.6 Slope ………………………………………. 9

3.2 Fire Intensity Model ………………………………………. 9 3.3 Behaviour of Different Types of Fires ………………………………. 10 3.4 Conclusions …………..…………………………... 10 3.5 Effects of Fire in African Grasslands and Savannas ………………. 11

3.5.1 Type of fire ………………………………………. 11 3.5.2 Fire intensity ………….……………………………. 12 3.5.3 Season of burning ……………………………………….. 13 3.5.4 Frequency of burning ………………………………………. 14 3.5.5 Interactions between fire and herbivory ………………………. 15 3.5.6 Discussion ………………………………………. 16 CHAPTER 4 ………………………………………. 18 4. STUDY SITE ………………………………………. 18

4.1 Location and Description ………………………………………. 18 4.2 Geology and Soils ………………………………………. 19

4.2.1 Geology ………………………………………. 19 4.2.2 Soils ………………………………………. 20

4.3 Climate ………………………………………. 21 4.3.1 Introduction ………………………………………. 21 4.3.2 Rainfall ………………………………………. 21

A FIRE MANAGEMENT PLAN FOR THE OKAVANGO DELTA RAMSAR SITE

IN BOTSWANA

W.S.W. Trollope, L.A. Trollope, C.de B. Austin, A. Held, A. Emery & C.J.H. Hines

Draft Report

EnviroNet Solutions Pty Ltd P O Box 2792, Nelspruit, South Africa Tel: +27 13 753 3370; Fax: +27 13 755 1214

Email: [email protected]

June, 2006

Documents

Fire management plan ODMP Draft Report First Section June 2006