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Mekelle University
College of Dryland Agriculture and Natural Resources
Department of Animal, Rangeland and Wildlife Sciences
Woody Plant Expansion and its Socio-economic Consequences
on Livelihood of Pastoralists of Telalak Woreda in Afar Regional
State.
By: Mulutsehay Abera Haile eyesus
A Thesis Submitted in Partial Fulfillment of the Requirements for
the Master of Science Degree
In
Livestock Production and Pastoral Development
Advisor:
Yayneshet Tesfay (PhD)
February 2012
ii
Declaration
This is to certify that this thesis entitled “Woody Plant Expansion and its Socio-Economic
Consequences on Livelihood of Pastoralists of Telalak woreda in Afar National Regional
State ” submitted in partial fulfillment of the requirements for the award of the degree of M.Sc.,
in Livestock Production and Pastoral Production to the College of Dry land Agriculture and
Natural Resources, Mekelle University, through the Department of Animal, Range and Wildlife
Sciences, done by Mr. Mulutsehay Abera H/eyesus, Id. No. FDA/PGR 047/02 is an authentic
work carried out by him under my guidance. The matter embodied in this project work has not
been submitted earlier for award of any degree or diploma to the best of my knowledge and
belief.
Name of the student Signature & date
Name of the supervisor Signature & date
iii
College of Dryland Agriculture and Natural Resources
Department of Animal, Rangeland and Wildlife Sciences
Thesis approval form for internal examiners
I, _________________________________ as internal examiner of student MULUTSEHAY
ABERA H/EYESUS would like to testify that all the comments made during thesis defense have
been included in the thesis.
Signature Date
Student _________________ _________________
Internal Examiner _________________ _________________
Head, department _________________ _________________
iv
Acknowledgement
I wish to extend my sincere gratitude and deepest appreciation to my advisor Dr. Yayneshet
Tesfaye for his tireless support and unreserved assistance I have received. I would also like to
thank Telalak woreda administrative staffs for their cooperation in providing smooth, fast, and
responsive supports and all my friends, especially Mr. Adefris Dagne and Mr. Ibrahim, for their
moral and technical support.
My thanks also go to Rural Capacity Building Project (RCBP) for the financial support, Afar
Pastoral and Agro-pastoral Research Institute (APARI) for all-round supports and granting me
the study leave. I am also pleased to acknowledge Mr. Sirak Alemayehu for his unreserved
support and encouragement, of which I accredited sincerely. In addition, I would like to thank
Mr. Aragawu Mekonnen for his GPS support. I also would like to thank Mr. Yasin, Mrs. Zinetu
Mohammed and others, who directly and indirectly contributed for the accomplishment of the
thesis.
I also extend my heartfelt respect and deepest love to my mother Mrs. Tsehay Amare, for her
continued support and encouragement; and my wife Radia Mohammed and my daughter Nadia
for their love, encouragement, and invaluable support throughout my studies.
v
Dedication
This thesis is dedicated to my daughter, Nadia Mulutsehay.
vi
Abstract
A study was conducted to identify and document pastoralists’ perception and adaptation to
woody plants expansion; consequences on the socio-economic transformation of pastoral
livelihoods; assess degree of woody species encroachment as measured by density, cover,
dominance, and species composition; and identify encroaching woody plants in Telalak woreda,
West-southern part of Afar National Regional State. Single visit formal survey and vegetation
sampling survey were employed to gather data. Based on the present vegetation cover situation,
and distribution of woody species the woreda stratified into encroached and unencroached sites.
Interview, group discussions and personal observation were employed to assess the socio-
economic impact on livelihood and their perceptions towards encroachment. For the vegetation
field sampling, 17 line transects of each with a length of 400 m and Width of 10 m stretched
randomly at different points as sampling units. In each transect four plots with equal size of 100
m2 were placed at 100 m interval and used for measuring woody vegetation density and diameter
at breast height. Canopy cover was measured using 14 transects (seven transects in each site)
with a length of 100 meter by line intercept method. The majority of the respondents 77.5% in
encroached site disclosed that their rangeland was in poor condition due to climatic factors and
encroachment of Acacia mellifera and Acacia senegal. However, most of the respondents 45% of
unencroached site indicated their rangeland was in good condition. Frequency and pattern of
mobility, conflict occurrence, livestock productivity, income source, herd composition, food
insecurity and dependence on food-aid were different between sites. Practice of crop production
was higher 25% in encroached than unencroached site 5%. In the encroached site, the most
important and dominant species were Acacia mellifera and Acacia senegal with mean Importance
Value Index 115.91 and 99.67, respectively. In unencroached site Acacia tortilis, Salvadora persica,
and Acacia nilotica were the most important and dominant species with mean Importance Value
Index of 37.6, 35.5 and 33.1, respectively. The total mean density of woody plants was 2636.11 ±
66.16 and 1112.5 ± 32.39 plants per hectare in encroached and unencroached sites, respectively.
The encroached site had less diverse woody species index than the unencroached site 1.23 Vs 2.7,
respectively. The encroached site was also less even than the unencroached with evenness index
of 0.45 and 0.92, respectively. Woody species similarity between the encroached and
unencroached site was 0.395 indicating low similarity of species composition between sites.
Density of woody plant saplings was different between sites. Acacia mellifera and Acacia senegal
saplings were found in higher proportion than other woody species saplings.
Key words: Acacia mellifera, Acacia senegal, encroachment, livestock, rangeland.
vii
Tables of contents
Declaration ................................................................................................................................. ii
Acknowledgement ..................................................................................................................... iv
Dedication ...................................................................................................................................v
Abstract .................................................................................................................................... vi
Tables of contents .................................................................................................................... vii
List of Tables ............................................................................................................................ ix
List of Figures .............................................................................................................................x
List of Appendices..................................................................................................................... xi
Abbreviations and Acronyms .................................................................................................. xii
Chapter I: Introduction ..............................................................................................................1
1.1 BACKGROUND ..................................................................................................................................................... 1
1.2 STATEMENT OF THE PROBLEM ........................................................................................................................... 3
1.3 SIGNIFICANCE OF THE STUDY ............................................................................................................................. 5
1.4 OBJECTIVES......................................................................................................................................................... 5
1.5 HYPOTHESIS ........................................................................................................................................................ 6
1.6 SCOPE AND LIMITATIONS OF THE STUDY ........................................................................................................... 6
Chapter II: Literature Review ....................................................................................................8
2. 1 THRESHOLDS FOR WOODY PLANT ENCROACHMENT ....................................................................................... 8
2.2 CAUSES FOR WOODY PLANT ENCROACHMENT ................................................................................................. 9
2.2.1 Climatic factors ............................................................................................................................ 9
2.2.2 Anthropogenic factors ............................................................................................................... 10
2.2.3 Secondary Succession ................................................................................................................ 13
2.3 CONSEQUENCES OF ENCROACHMENT .............................................................................................................. 15
2.3.1 Change in livestock Production System and Productivity ........................................................ 15
2.3.2 Socio-economic influences on pastoralists ............................................................................... 16
2.3.3 Rangeland condition and trend deterioration........................................................................... 17
2.3.4 Other changes ............................................................................................................................ 18
viii
Chapter III: Materials and Methods ........................................................................................ 19
3.1 DESCRIPTION OF THE STUDY AREA ................................................................................................................... 19
3.1.1 Geographical Location .............................................................................................................. 19
3.1.2 Soil, Vegetation and Water Resources ...................................................................................... 20
3.1.3 Agro-ecology and Climate ......................................................................................................... 21
3.1.4 Human and Livestock population ............................................................................................. 21
3.1.5 Farming system and land use .................................................................................................... 21
3.1.6 Conflict occurrence ................................................................................................................... 22
3.2 METHODS OF DATA COLLECTION .................................................................................................................... 22
3.2.1 Site Selection .............................................................................................................................. 22
3.2.2 Socio-economic Data Collection Procedures............................................................................ 23
3.2.3 Vegetation Data Collection Procedures .................................................................................... 25
3.3 DATA ANALYSIS ................................................................................................................................................ 29
Chapter IV: Results and Discussion ......................................................................................... 32
4.1 SOCIO-ECONOMIC SURVEY ............................................................................................................................... 32
4.1.1 Perception of Pastoralists on Rangeland Degradation and Encroachment ............................ 32
4.1.2 Pastoralists Adaptation to Woody Plants Expansion ............................................................... 36
4.1.3 Consequences of Woody Plants Expansion on the Socio-economic Transformation of
Pastoral Livelihoods .................................................................................................................. 38
4.1.3.1 Change in Pattern and Frequency of Mobility .................................................................................................... 38 4.1.3.2 Frequency and Causes of Conflict ....................................................................................................................... 39 4.1.3.3 Effect on Livestock Production ............................................................................................................................ 41 3.1.3.4 Effect on Household Income ................................................................................................................................ 43 4.1.3.5 Effect on Composition of Herd ............................................................................................................................ 44 4.1.3.6 Effect on Food Security and Attitude towards Agro-pastoralism ...................................................................... 45
4.2 WOODY VEGETATION ATTRIBUTES ................................................................................................................. 46
4.2.1 Woody Species Composition and Similarity ............................................................................. 46
4.2.2 Woody species density ................................................................................................................ 49
4.2.3 Woody species canopy cover ...................................................................................................... 52
4.2.4 Woody species Diversity and Evenness ..................................................................................... 53
4.2.5 Encroaching woody plant species ............................................................................................. 54
Chapter V: Conclusions and Recommendations ....................................................................... 57
References ................................................................................................................................. 61
APPENDIX ............................................................................................................................... 71
ix
List of Tables
Table 1. Causes of change in rangeland condition in encroached and unencroached sites in
Telalak woreda as ranked by respondents. ...................................................................... 32
Table 2. Major encroaching woody plant species in encroached and unencroached sites in Telalak
woreda as ranked by respondents. ................................................................................... 34
Table 3. Livestock production constraints in encroached and unencroached sites in Telalak
woreda. ............................................................................................................................ 41
Table 4. Woody vegetation species composition in encroached and unencroached sites in Telalak
woreda in Afar region. ....................................................................................................... 47
Table 5. Average total density (N/ha), saplings density (N/ha) and canopy cover (%) of woody
plant species in encroached and unencroached sites in Telalak Woreda in Afar region
(Mean ± SE). ................................................................................................................... 50
Table 6. Mean density of woody species saplings and their relative contribution to the total
woody species sapling density, in encroached and unencroached sites in Telalak woreda
in Afar region. ................................................................................................................. 51
Table 7. Species diversity (H‟) and evenness index (J) of woody plant species in encroached and
unencroached sites in Telalak Woreda in Afar region. ................................................... 53
Table 8. Woody vegetation relative dominance and importance value index in encroached and
unencroached sites in Telalak woreda. ................................................................................ 55
x
List of Figures
Figure 1. Location of the study area .............................................................................................. 19
xi
List of Appendices
Appendix 1. Household Survey Questionnaire ............................................................................. 71
Appendix 2. Cross tabulation and chi-square test results for socio-economic survey ..................... 75
Appendix 3. Woody Species Attributes ....................................................................................... 76
Appendix 4. Woody Species Data ............................................................................................... 77
Appendix 5. Species Diversity along Transects ............................................................................ 77
Appendix 6. Evenness of Species along Transects........................................................................ 77
Appendix 7. Cross tabulation and chi-square test of species attributes between the two sites ......... 78
xii
Abbreviations and Acronyms
AMNRS Amhara National Regional State
ANRS Afar National Regional State
APARI Afar Pastoral and Agro-pastoral Research Institute
APARDB Afar Pastoral, Agricultural and Rural Development Bureau
CSA Central Statistical Agency
GPS Geographical Positioning System
ILCA International Livestock Center for Africa
ILRI International Livestock Research Institute
IVI Importance Value Index
NARSC National Applied Resource Sciences Center, Colorado
NGOs Non-Governmental Organizations
PCDP Pastoralist Community Development Project
RAAR Regional Atlas of Afar Region
SEM Standard Error of Mean
TWSPD Telalak Woreda Strategic Planning Document
W Mann Whitney test value (W value)
WARC Warar Agricultural Research Institute
WBISPP Woody Biomass Inventory and Strategic Planning Project
1
Chapter I: Introduction
1.1 Background
Rangelands represent an important resource in many countries around the world. About 30 to 40
million people in arid and semiarid regions have “animal based” economies (Sand ford, 1983, as
cited in Holecheck et al., 1995). Pastoralists derive most of their income and subsistence from
livestock grazing in arid and semiarid rangelands. Rangelands in many countries are being
stressed to meet a growing human population dependent on a shrinking resource base (Holecheck
et al., 1995).
Rangelands in Ethiopia have different socio-economic values. These include livestock feed
supply, resource extraction, source of medicinal plants and sites for tourist attraction and various
traditional ceremonies. They are also part of the rural people‟s economy yielding economic
benefits and they traditionally play an important role for rural communities. Generally,
rangelands contribute largely to the economies and welfare of the communities of the lowland,
which depend, directly or indirectly, on the exploitation of the natural resources of these
ecosystems.
There are interrelationships between rangelands and socioeconomic conditions prevailing in these
areas. On one hand, socioeconomic conditions in lowlands are usually affected by the natural
environment with its various ecosystems which provide a continuous supply of goods including
meat, milk, animal feed, fire fuel, construction materials, and other services including soil
protection, sustaining bio-diversity, water quality maintenance, recreation and tourism. On the
other hand, socioeconomic structures in lowland area may affect positively or negatively the
2
rangeland and its ecosystems by various human activities being conducted in these areas. This, in
return, means that the stability of rangelands and the community welfare are highly associated.
Rangelands, when properly managed, have for centuries provided feed for grazing and browsing
livestock under extensive systems, which are acceptable living conditions for populations in the
arid and semi-arid areas of the world (El-shorbagy, 1998). The rangelands in Ethiopia cover
about 60% land surface and are home to about 12% and 26% of the human and livestock
populations of Ethiopia, respectively (Coppock, 1994).
In the past 50 years, evidence has accumulated that indicates savannas throughout the world are
being altered by a phenomenon known as 'bush encroachment' (Archer et al., 2001). Brown and
Archer (1999) and Bok (1999) considered the process of expansion of woody species into
grassland as shrub invasion. Esselink et al. (1991) described bush encroachment as the
replacement of grassland with vegetation dominated by woody species. Meika et al. (2001)
defined bush encroachment as “the conversion of savannas to dense, acacia-dominated thickets
with little grass cover”. Berhanu (2007) indicated that acacia species are the dominant shrubs
identified that form a dense thicket, which is very difficult to penetrate because of their thorn and
dense short canopy. Acacia mellifera (Black thorn), Acacia nilotica and Catophractes alexandria
may also be thicket forming and can be taken as encroaching woody species (Christian, 2010).
In Ethiopia, there are about 22 invasive species of which Mesquites (Prosopis juliflora), and
different Acacia species (Acacia mellifera, Acacia etbaica, Acacia nubica, Acacia senegal,
Acacia brevispica and Drepanolobium robustus) were identified as aggressive encroaching
species and are causing major problems in the lowlands of Afar (MOA, 1997). The rapid spread
of woody plant presents a number of social, ecological and economic concerns. Bush
3
encroachment reduces the carrying capacity for livestock. The reduction in carrying capacity is of
great significance because savannas contain a large and rapidly growing proportion of the world‟s
human population, including many pastoralists whose livelihood is threatened by this process
(Archer et al., 2001). Encroachment of woody plants has been among the major threats to the
livelihoods of pastoralists and their ecosystem (Gemedo et al., 2006).
1.2 Statement of the Problem
An increase in density of woody plants beyond a critical density suppresses herbaceous plant
production (Oba et al., 2000; Richter et al., 2001) mainly due to severe competition for available
soil water (Richter et al., 2001). Woody plants encroachment into grassland and savanna can alter
soil moisture and nutrients, and can suppress grass productivity (Richter et al., 2001; Roques et
al., 2001).
Berhanu (2007) also showed that large proportion of the changes of grass to other classes
occurred by encroachment of shrubs. In addition, the average rate of change from grassland to
shrubs in 20 years time was about 228 ha per year. He also indicated the presence of very high
negative correlation (- 0.95) between grass and shrub cover. Gemedo et al. (2006) also indicated
that woody plants are negatively correlated with herbaceous biomass.
Current population growth and mismanagement, reluctance to manage rangelands, and unplanned
development activities are placing increasing pressure on rangelands, causing a wide range of
problems (Yayneshet and Kelemework, 2004). These problems range between environmental
degradation, biodiversity loss and productivity loss, leading ultimately to the breakdown of
4
socioeconomic systems. Such a pressure poses increasing threats to rangeland ecosystems that
may lead to degradation of resources.
Most rangelands are severely degraded and most of the fauna and flora species are endangered
(WARC-APARI, 2007). Although rangeland ecosystems are among the productive ecosystems
on earth, the current rangelands‟ status in general and their ecological functions and values to
societal benefits in particular remain little understood and poorly addressed issues. Thus, many
rangeland ecosystems are regarded as wastelands (WARC-APARI, 2007) and continue to be
depleted at an alarming rate.
The rangeland of the study area is no longer able to sustainably support cattle production. Only
camel and goats are viable in the absence of irrigated pasture (Philpott et al., 2005). This is
because different animal species are adapted to different types of rangelands. Forage preference
of grazing animals is major deciding factor of type of animal in a particular rangeland. Cattle are
generally well suited to rangelands covered by tall and coarser grasses (Holecheck et al., 1995).
The expansion of woody plant species in the rangelands of Hari Resu, South-western of Afar
Regional State, specifically Telalak woreda, is increasing at higher rate from time to time
particularly after the droughts of 1980s and 1990s. According to the herds‟ man in the area, this
rapid expansion of indigenous encroacher acacia species, has decreased their rangeland
productivity and affected the pastoralist livelihoods.
Kassahun et al. (2008) showed that changes in vegetation ecology in the Somali region of
Ethiopia have drastically altered the livestock species composition in favor of camels and small
ruminants than cattle. This has also influenced the planning and preference of pastoralists for
5
different types of livestock. Poor and very poor households have emerged, and the above-medium
wealth rank has disappeared, showing that poverty has increased over time.
1.3 Significance of the Study
There is a need to evaluate the ecological distribution and socioeconomic impact of the
encroaching woody species to take appropriate management and control measures (Haysom and
Murphy, 2003). The socio-economic values of woody plants are appreciated, but their negative
effect is little understood, and has not yet been well studied in the study area.
Assessing the prevailing ecological and socioeconomic conditions, with respect to woody plant
expansion, in order to develop sustainable strategies to control further encroachment and improve
the living condition of pastoralists is necessary. So, it was imperative to study the nature of
woody plant expansion and its socio-economic impact on pastoral livelihoods in Telalak woreda
in Hari Resu, Afar National Regional State.
1.4 Objectives
The general objective of this study was to understand the degree of influence of encroaching
woody plants on the overall livelihood of pastoralists who depend on the balance between
herbaceous and woody species as well as productivity of the rangelands in the study area.
The specific objectives of this study were to:
1. Identify and document pastoralists‟ perception and adaptation to woody plants expansion in the
two sites that differed in their degree of encroachment by woody species.
6
2. Investigate the consequences of woody plant expansion on the socio-economic transformation
of Afar pastoral livelihoods in relation to their production system, mobility, conflict,
productivity, food security, herd composition and structure, and household income in the two
sites that differ in the degree of encroachment by woody species.
3. Examine woody vegetation attributes in terms of species composition, density, cover,
dominance, diversity and evenness; and identify top encroaching species in the two sites.
1.5 Hypothesis
It was hypothesized that, woody plant expansion has not been realized to substantially and
markedly influence the livelihoods of the pastoralists living in Telalak woreda of Afar region in
Ethiopia. Furthermore, pastoralists of the district are not able to adapt and do not appreciably
perceive the problem of woody plant expansion. In addition, the selected vegetation attributes
(cover, density, frequency, species composition, and diversity) will not significantly differ in
rangelands that appear encroached and normal.
1.6 Scope and Limitations of the study
The process of encroachment of grazing lands by bush/ shrubs is strongly affected by many local
factors (topography, soil characteristics, rainfall distribution, fire, and anthropogenic
disturbances). However, it was difficult to study and determine the contribution of each factor to
the problem at the level of this study, due to budget and time constraint. However, since
rangeland encroachment is the result of the combined effect of these factors, further study to
understand the mechanism of woody species expansion and the relation of these factors to the
problem in the study district is necessary.
7
The study mainly focuses only on woody plant species and their attributes. It did not evaluate the
effect of woody species expansion on herbaceous plant species, soil, and other aspects of the
rangeland ecosystem. However, to get full picture of the problem detailed study on herbaceous
plants and other component of the rangeland should be done.
Since the woreda administrative is established recently (after 1993), there was also lack of
documented quantitative data on many socio-economic aspects of the Afar pastoralists.
Therefore, many of the information‟s related to the socio-economic aspect were relied on key
informants and short period (1993 - 2010) secondary data.
8
Chapter II: Literature Review
2. 1 Thresholds for Woody Plant Encroachment
Bush encroachment is treated as the advancement of woody species into grasslands lowering the
grazing quality as well as limiting the accessibility of grazing lands (Tefera et al., 2006; Solomon
et al., 2007). Woody plants cover of 40%, which is approximately equal to a density of 2400
plants per ha, is assumed to be at equilibrium between the encroached and non encroached
condition (Roques et al., 2001; Ayana, 2005) but 2500 plants per ha is an encroached condition
(Richter et al., 2001).
The rangelands of Borena, southern Ethiopia, with woody plant density of 3014 plants per ha and
canopy cover of 52%, were considered as crossed the critical threshold level and entered into the
encroached condition (Gemedo et al., 2006). Teshome et al. (2009) reported woody species
density of 2454.9 plants/ha, was on the border between encroached and non- encroached
condition in Bale zone, southern Ethiopia. In addition, in southern Ethiopia, Ayana and Oba
(2007) reported that woody species density 3995 stems per ha was estimated in encroached
rangeland.
Generally, information on the level of encroachment of Afar rangelands by indigenous woody
plant species, particularly of the study area was not available. However, estimating the degree of
encroachment of these rangelands helps to design appropriate measure to treat these encroached
rangelands and to prevent further expansion of woody plants on normal rangelands.
9
2.2 Causes for Woody Plant Encroachment
The cause of change in vegetation cover is a subject of controversy in different parts of the world,
and several authors relate it to the local driving forces (Moleele et al., 2002; Laliberte et al.,
2004; and Tefera et al., 2006). One or the combination of natural and human-made policy
measures, land use and other socio-economic factors influence the process of woody species
encroachment. The combined effects of human activities and natural factors such as climate
change lead to the depletion of natural vegetation and drastic decline in dry land productivity.
These eventually result in land use/land cover changes and desertification processes (Haysom and
Murphy, 2003). However, local herders, district administrative and professionals on the discipline
(WARC-APARI, 2007) believed inappropriate rangeland management and the droughts of 1980s
and 1990s are the only known causes that result the rapid expansion of indigenous encroacher
acacia species in Telalak woreda.
2.2.1 Climatic factors
Shrubs had the ability to overcome moisture stress through tapping water and nutrition deep from
the sub-surface soil. Long persisted drought, which was caused by climate change, had been the
major factor for shrub establishment in southern United States (Laliberte et al., 2004). Occasional
periods of rainfall well above the average have also been indicated as a cause for woody species
to withstand dense grass communities (Tainton, 1999).
Rainfall amount and frequency may play a key role in the occurrence of bush encroachment
because trees require more rain to germinate than do grasses and may germinate in mass with or
without grazing in rare, high rainfall years. This leads to the formation of distinct cohorts of trees
of a single size and presumably age (Britz and Ward, 2007). According to herders, even though
10
climate change has been believed as the main cause for the expansion of acacia species in
southwestern Afar rangelands, lack of long time data on frequency and distribution of rainfall in
the area makes difficult to decide the extent of contribution of drought to woody plant invasion
beside other additional factors (WARC-APARI, 2007).
2.2.2 Anthropogenic factors
An indicative of the broader range of human disturbances to rangelands is needed to capture the
full range of the sources of stress to rangeland health. Assessing the degree of disturbances to the
rangelands from land uses (agriculture, settlement, and grazing) and inappropriate management is
essential. Yayneshet and Kelemework (2004) also indicate the effect of anthropogenic factors had
resulted dramatic change on the pattern of natural resources and its management in 4-5 decades in
northern Afar region. The appearance of invasive woody plant species can occur due to
mismanagement of resources by the following anthropogenic factors.
Overgrazing
When overgrazing occurs, the grasses are removed, freeing up water and soil resources for the
trees to exploit. Tree seeds are then able to germinate in mass, creating an impenetrable thicket
(Britz and Ward, 2007). In Southern African rangelands (Bok, 1999; Moleele et al., 2002) and
the wide Borena semi arid rangelands of Ethiopia (Tefera et al., 2006), there are evidences that
suggest the main cause for shrub encroachment is attributed to anthropogenic factors mainly over
grazing. Overgrazing has been also described as one of the causes for invasion by shrub in
southern African grassvelds (Tainton, 1999).
11
As grazing pressure increased on palatable grass, unpalatable herbs and shrubs increased getting
an opportunity to utilize the limited nutrient and moisture available (de Leeuw et al., 2001).
Coppock (1993) also indicated that sites that endured heavy grazing pressure to have high
densities of very young woody plants in Borana Rangelands in southern Ethiopia.
In African savannas, an intense cattle grazing is commonly associated with an increase in woody
vegetation (Riginos and Young, 2007). Overgrazing, results in denudation of grasslands by
giving bush a competitive advantage for soil moisture in the early stages of seedling
establishment (Christian, 2010). Ayana and Oba (2007) indicated that increased grazing pressure
promotes bush cover on grazing lands of southern Ethiopia.
Encroachment of woody plants on most Afar rangelands are closely correlated with the activities of
man such as overgrazing (Diress, 1999). Other report (ESGPIP, 2009) also indicates overstocking
to be a serious problem in the Afar and Somali rangelands that creates imbalances on the natural
resources by causing bush encroachment. In Telalak woreda, overgrazing results the destruction of
grasses, which in turn increased the competitive ability of woody vegetations and contributed to their
encroachment (WARC-APARI, 2007).
Fire suppression
Study by Muriuki et al. (2005) indicated that decrease in the recommended fire occurrences,
resulted in sever shrub encroachment. Reduction in fire frequency and/or intensity can promote
shrub establishment, because of the more susceptibility of shrubs to fire than grasses (Thomas
and Douglas, 1999). In the absence of fire, woody vegetation increases both in cover and in
height (Adam et al., 2001). In the East African savannas the suppression of fire is often
associated with increased bush encroachment and loss of herbaceous plants (Smit, 2003)
12
In Borena rangelands of Ethiopia Solomon et al. (2007) perceived problem of bush encroachment
and the ban on traditional burning practices as aggravating factor to the invasion process.
Gemedo et al. (2006) also reported absence of fire to be perceived as a major factor for
encroachment of woody plants.
The reduction of herbaceous layer due to the recurrent droughts and over grazing reduce the fire
fuel in the southwestern rangelands of Afar. The presence of insufficient fuel to sustain wild fire
or use of fire by pastoralists for the management of woody vegetation and to increase quality of
grass has been decreasing from time to time and contributed for woody vegetation encroachment.
Environment policy and weak traditional pastoral rangeland management systems
Pastoralists are very frequently blamed for the alarming deterioration rate in the natural resources
of rangelands in terms of overstocking and mismanagement (lack of fire, controlling access to
over utilized rangelands and endangered species) of the land. This viewpoint should be put in
perspective; because pastoralists‟ actions are sometimes dictated by forces beyond their control
(Gemedo et al., 2006). Yayneshet and Kelemework (2004) indicated that the Afar pastoralists
well understood the capacity of their rangeland and they used to exercise careful timing of
grazing. However, due to the aggravating natural pressure (drought and high population) on the
rangelands, currently they are unable to apply the traditional management system indicating the
need to strengthen the traditional management system.
The other problem is wrong pastoral development interventions in design and priority setting.
Most projects were not able to meet expectations and there is no any viable pastoral development
in Afar region. Projects were framed by the old style of pastoral development model and
targeting increasing meat supply for the market (Yayneshet and Kelemework, 2004). Lack of
13
understanding of the relationship between the environment and pastoralists and ignorance
regarding the perception of the pastoralists may also contribute to the misunderstanding of the
pastoral production system and the priority needs of the pastoralists (EARO, 2002).
Projects or policies were not designed related to rangeland resource management specifically
related to bush encroachment control and rehabilitation in the region. Yayneshet and
Kelemework (2004) reported that the current planning approach in the Afar region is likely to
contain the most pressing problems like lack of appropriate land use planning which resulted
ineffective rangeland resource management and degradation of most of the rangelands in the
region.
Therefore, as stated by Werner (2001) it is imperative to scrutinize and analyse the environmental
policy in which the sector has to perform. Revising the environment policy and relevant
legislation with regard to rangeland management and bush encroachment is important.
2.2.3 Secondary Succession
Besides other causes, we need also to realize that slow expansion of woodlands into grassland
due to secondary succession. secondary succession is the process whereby one land which
previously has been occupied by highly developed vegetation destroyed by some unusual factor
such as fire, drought, etc and replaces another species or association of species (Holecheck et
al., 1995). Studies conducted by Parolin (2006) and Vogot et al. (2006) indicated that,
extraordinary disturbance (flood) plays a major role in seed dispersal and could favor shrubs to
encroach wide areas of grasslands. Dryland ecosystems are considered disequilibrial, changing
14
from one state to another due to strong external factors e.g. droughts, fires, or insect attacks
(Hanne, 1999).
In many grassland ecosystems, botanical structure has been or is being greatly modified by over-
grazing, weed invasion and effects of climate which results to „transition‟ from one discrete or
stable „state‟ of the vegetation to another. In arid and semi-arid areas, the overriding influences
on plant community structure and succession are management (e.g. stocking rate effects) and
periodic climatic events (Tow and Lazenby, 2001). Bush encroachment may be a natural phase in
the patch dynamics of savannas that are driven by rainfall patterns. Any process that creates
space in the grass sward be it fire, grazing or other disturbance, will lead to encroachment if the
rainfall conditions are appropriate (Britz and Ward, 2007). Wiegand et al. (2002) have also
hypothesized that bush encroachment in many semi-arid and arid environments is a natural
phenomenon occurring in ecological systems governed by patch dynamic processes.
The encroachment of woody vegetation into open savannah has been attributed to direct and
indirect effects of heavy grazing by livestock, perhaps through interaction with changes in
climate or atmospheric composition. By their direct and indirect effects on ecosystem processes,
they may cause rapid successions or switches between different states of a system (Christina,
2001). In Eastern Africa, as indicated by Herlocker (1999) the trend of natural succession of
vegetation is towards woody vegetation.
In the study area, the observed change (rapid succession) from wooded grassland to acacia
dominated shrub land is believed to be brought by the recurrent droughts in the past three decades
and overgrazing. Range succession model, which is the main management tool for rangelands,
15
have to be developed to assess the rangeland condition and dynamics and to decide the
appropriate management action that should be taken to maintain or achieve the desirable state.
2.3 Consequences of Encroachment
2.3.1 Change in livestock Production System and Productivity
Grassland which is the major source of pasture has been continuously replaced by shrub land
(Berhanu, 2007), and thus pasture production on rangelands is declining, that in turn leads to
change in livestock production system and productivity. Encroachment of woody plants is
continuously threatening the pastoral production and challenging the sustainability of livestock
(Solomon et al., 2008).
In Namibia, due to bush encroachment cattle numbers on commercial farms decreased from a
peak of 2.6 million in the late 1950s to 1.2 million by the mid 1990s (Lange et al. 1997). Bush
encroachment has caused a major decline in the productivity of cattle, sheep and wildlife
ranching systems over 20 million hectares in South Africa (Britz and Ward, 2007). The expansive
nature of bush encroachment implies bush-dominant land would be created and consequently
pastoral production figures affected, due to the loss of ecosystem heterogeneity (Dougill and Cox,
1997).
In Borana rangelands, southern Ethiopia, Gemedo et al, (2006) found encroachment of woody
plants to have decreased rangeland condition and grass availability, which resulted to decrease in
herbaceous biomass production and the livestock production was affected. The rangeland in Afar
is no longer able to sustainably support cattle production, only camel and goats are viable in the
absence of irrigated pasture (Philpott et al., 2005). Change in herd size and composition to satisfy
16
the maintenance requirements of a pastoral household were also reported by Yayneshet and
Kelemework (2004) in north Afar Pastoralists because of change in vegetation cover.
In Telalak woreda, even though bush encroachment has greatly affected the pastoral production
system and productivity of livestock in which the livelihood of the pastoral community depends,
there is no enough documented information how much the problem affected the production
system and productivity of livestock.
2.3.2 Socio-economic influences on pastoralists
Vegetation cover change can bring many social and economical changes on the pastoral
community. For example, In Somali region, eastern Ethiopia, changes in vegetation ecology has
drastically altered the livestock species composition in favor of camels and small ruminants
rather than cattle (Kassahun et al., 2008). This has also influenced the planning and preference of
pastoralists for different types of livestock. Poor and very poor households have emerged, and the
below-medium wealth rank has disappeared, showing that poverty has increased over time
(Kassahun et al., 2008). Study by Yayneshet and Kelemework (2004) also indicated that, related
to land use/ land cover change, many socio-economic changes such as starting of cultivation,
migrating to emerging towns and other areas, and following different livelihood strategies could
happen in pastoral areas.
In Telalak woreda, encroachment of woody vegetation also causes unavailability and reduction of
grass from rangelands. Even during wet season the amount of feed available on rangelands
cannot sustain the existing livestock number (WARC-APARI, 2007). The condition results an
increase in frequency of mobility by pastoralists to neighboring areas in search of feed for their
17
livestock. In turn occurrence of conflict for resources with neighboring areas was also increased
(WARC-APARI, 2007).
2.3.3 Rangeland condition and trend deterioration
The general trend of grasslands in arid and semi-arid areas is in a continuous decline in terms of
grass cover, but remarkable rise in shrub cover (Berhanu, 2007). The increment of bushes causes
a decrease in pasture land as well as pasture capacity, soil erosion, poor productivity. Poor soil
condition and loss of vegetation cover results in high run off which rain water cannot soak into
the ground, due to this, the development of artificial drought could also occur (Gemedo et al.,
2006).
As grass production per unit of land becomes less than the requirement by animals, over grazing
and biomass depletion will occur. This further give way for shrubs to easily expand by using the
less competitive advantage created for available limited moisture and nutrient. As encroachment
continues, it obviously lead to the gradual decline in carrying capacity of grasslands through time
(Berhanu, 2007).
According to Riginos and Young (2007) „„Woody‟‟ or „„bush‟‟ encroachment can have profound
negative consequences for native fauna and rangeland productivity. Britz and Ward (2007) also
indicated that when bush encroachment occurs, multi-species grass swards in open savannas will
be replaced by virtually impenetrable thickets of a single species of thorn tree. Bush
encroachment may affect rangeland condition negatively in terms of botanical composition,
forage productivity, soil erosion and biodiversity loss (Melesse, 2003). The condition of the
rangeland in the study area had been deteriorating from time to time and reaching to the condition
18
that it cannot support the pastoral production system any more without the use of irrigated
pasture.
2.3.4 Other changes
Most acacia encroacher‟s forms dense, mono-specific thicket which supports reduced diversity of
plants (Heard et al., 2005). The effects of these species can result change in the availability of
resources and ecosystem structure and function. The change in ecosystem function can brought
about extinction of indigenous plant species (Abdillahi et al., 2005). Habitat change due to
encroachment could also bring change in wildlife population dynamics (Berhanu, 2007).
Unavailability of grass from rangelands causes pastoralists to move to neighboring areas in
search of feed for their livestock. Even during wet season, the amount of feed available on these
rangelands cannot sustain the existing livestock number. During mobility, there is a conflict for
the same resource with neighboring areas (WARC-APARI, 2007). Piguet (2002) also reported
movements of livestock from the study area to the Amhara regional border due to grazing
shortages because of poor rangeland condition causes clash with Oromo agro-pastoralists.
WARC-APARI (2007) report indicates the loss of indigenous herbaceous and woody plant
species due to encroaching acacia species becomes a great problem in the Southwestern
rangeland of Afar.
19
Chapter III: Materials and Methods
3.1 Description of the study area
3.1.1 Geographical Location
The study was conducted in South-Western Afar National Regional State, Hari Resu (formerly
called zone 5 administrative), Telalak woreda. The study area is found at 40012' - 40
039' E and
1105' - 11
015' N and is bordered by Gewane woreda to the east, Dewe woreda to the south,
Oromia zone of ANRS in the west and Adear woreda in the north.
Source: GIS department of Afar Finance and Economy Development Bureau
Figure 1. Location of the study area
20
The capital of Telalak woreda, Nemalefen is about 205 km far from the regional capital city
Samara. The study area has a total area of 139,084 ha. The elevation of the area ranges from 700
meters above sea level to 1045 meters above sea level (RAAR, 2006).
For this study, two sites that represent the woreda with nine kebeles were selected. From the first
site, four kebele‟s (namely: Telalak & Abaro, Aware & Areda, Geysu & Dewe, and Adalil) that
are located on the foot of the escarpment of the highlands of Amhara Regional State,
representing the encroached site (here in after called Site I); and from the second site, five
kebele‟s (namely: Odole & Asbole, Heberto & Rasa, Gewis & Hamedudas, Waydolele & Yealo,
and Heberto & Rasa) that are adjacent to the Awash River representing the unencroached site
(here in after called site II), where used for data collection.
3.1.2 Soil, Vegetation and Water Resources
The major soil types in the study area are Lithosols 0.5%, Regosols 18.88%, Haplic Solonchak
17%, Eutric Fluvisols 25.5%, Calcaric Fluvis 40.2%, Rock surface 12.3% and Calcaric
Cambisols 4.5% (WBISPP, 2002). According to RAAR (2006), in site I the main type of soil are
Calcaric Cambisols and Lithic Lithosols. However, in site II Eutric Fluvisols, Haplic Solonchak
and Calcaric Fluvis are the main soil types.
Information for each specific site were not obtained, however grass species include Vissia
cuspidata, Cynodon dactylon, Sporobolus pellucidus, Ischaemum afrum and Cymbopogon
schoenthus. Browse trees include Grewia ferruginea, Grewia villosa, Balanites aegyptica,
Salvadora persica, Acacia senegal and Acacia mellifera, Acacia nilotica, Acacia tortilis, Acacia
horridae, and other plants (RAAR, 2006). The study area has four permanent rivers namely
Awash, Wata, Telalak and Gewis; and numerous temporary rivers (RAAR, 2006).
21
3.1.3 Agro-ecology and Climate
The area is characterized as semi-arid type of agro-ecological zone, with low and erratic rainfall,
high temperature and evapo-transpiration. Rainfall is bi-modal with a mean annual rainfall 750
mm and ranges from 300 mm to 900 mm. The area receives three rainy seasons. The main rain,
kerma accounts for 60% of annual rainfall and is from mid-June to mid-September. Rainy
showers follow this kerma in mid-December called dedea and there is a minor rainy season
during March-April called sugum. Temperature of the area ranges from 22.5ºC to 27.5ºC (RAAR,
2006).
3.1.4 Human and Livestock population
The total population of the woreda is estimated about 81,274 of which 58% (47,284) are male
and 42% (33,990) are female. The average family size is seven people per household (CSA,
2007). The total number of livestock is estimated to be cattle 91,959 (20.8%), sheep 99,874
(22.6%), goat 189,246 (42.8%), camel 54,983 (12.4%), and equines 6,472 (1.4%). Density of
livestock is 200-400 per square kilometre (CSA, 2007). However, the total livestock population is
believed to be reduced by half because of the drought and related disease outbreak in 2008-2009
(APARDB, 2010).
3.1.5 Farming system and land use
Although pastoralism is the dominant occupation in the area, crop production is becoming an
important component of the system expanding from time to time in different Kebeles of the study
area. The woreda contains 11 Kebeles of which six Kebeles are pure pastoralists; five Kebeles are
recently converted agro-pastoralists. According to WBISPP (2002), the dominant land cover type
22
of the woreda are cultivated land 0.09%, grassland 24.2%, shrub land 60.6%, riverine forest
0.778%, water bodies 0.003, wet land 0.012, and bare land 14.29%.
The production system is predominantly pastoral (97.2%) and agro-pastoral (2.8%) with an
average land holding size of 1 – 2 ha/ household. The livestock entirely depend on natural
vegetation. Pastoralists who depend on livestock and are nomadic and transhumant in their
lifestyle that use much of the land for natural fodder along with livestock production; agro-
pastoralists cultivate small farms for subsistence. The main crops grown by agro-pastoralists are
maize, sorghum, oil crops, vegetables such as tomato, onion, and red pepper; and vegetables such
as orange, banana, lemon, papaya, and mango (TWSPD, 2010).
3.1.6 Conflict occurrence
According to the woreda administration office, conflict in the Woreda was severe in 1991 – 2000
in both sites. In site I, bush encroachment contributed for feed shortage on grazing lands; and the
mobility of pastoralists and conflict occurrence were increased.
3.2 Methods of Data Collection
3.2.1 Site Selection
Prior to the selection of rangeland sites, relevant documents on the nature of the vegetation, soil
and other features of the study area were collected, reviewed and examined from published and
unpublished materials (woreda and regional office records). Discussions were also made with
different stakeholders (community members, elders, and woreda administrative persons) about
the nature, types and distribution of woody vegetations and pastoralist‟s distribution and
condition. Finally, a reconnaissance survey was made for the identification of the rangeland sites.
23
The study area was classified into two distinct categories (ecological sites) as encroached and
unencroached sites. The ecological sites were classified and selected based on the level of
encroachment by personal observation of the sites and distribution of encroaching acacia species
by discussing with elders, the information gained from the woreda pastoral and agricultural
development office head and experts. The two chosen sites were similar in many aspects such as
altitude, topography, climate (rainfall and temperature) and production system; however,
different in the level of woody species encroachment, soil and soil moisture content.
3.2.2 Socio-economic Data Collection Procedures
A total of 80 households from the whole study area were used for the study. From each
ecological site, 40 households were randomly selected and interviewed. A single-visit formal
survey method (ILCA, 1990) was followed to gather data.
Before starting the main survey, the questionnaire was pre-tested out using a small sample of
units that were not involved in the main survey. This was to see whether the questions were
suitable and to gauge the responses thereby to refine, adjust, and further develop the tools. Heads
of households were interviewed using a structured and semi-structured questionnaire. In addition,
group discussions composed of key informants and elders (8-10 persons per group), were held in
each kebele to obtain in-depth information and opinions on the issue. Informal interview with
local peoples at various levels were also made to explore their perception on rangeland condition
and woody plant expansion; adaptation strategy; and the economic and social impact of
encroachment on livelihoods.
24
Pastoralist’s perception towards rangeland condition and woody plants expansion
Respondents were asked to rate the condition of their rangelands into three distinct classes (good,
fair, and poor) and identify the possible causes of rangeland condition change. The requirements
that were used to rate the rangeland conditions in the above three rates were the following. Good
condition (herbaceous/canopy layers are under-utilized or under grazed/browsed, with little or no
encroachment). Fair condition (moderately grazed/browsed, the bare ground is clearly visible,
palatable grass species are diminished while desirable browse plants are threatened; there is
moderate encroachment by unpalatable grasses, weeds, herbs and woody plants). And poor
condition (heavily grazed/browsed, more palatable and high producing grass species are
removed, basal cover reduced below 50% while the proportion of bare ground increase,
encroachment of harmful plants increase and the population of encroaching woody plants become
dominant) (Amaha, 2006).
Respondents were also asked their perception about the presence of encroaching woody species
in their rangelands, and if there any encroaching species, their perception about the causes for
expansion of these species were also assessed.
Pastoralist’s adaptation strategies to woody plant expansion and livelihood changes
Strategies that were used by pastoralists to cope up with changes that brought by encroachment
were also assessed. Information was also collected on household economic profiles (such as
livestock ownership, income, household economic activities, livestock productivity and practice
of crop production) to assess economical changes. Perception on their social conditions (conflict
due to grazing land, frequency and pattern of migration, dependency on food aid, food insecurity,
25
etc) were also asked to assess the social impact that has occurred on the pastoral community of
the area in the past 2-3 decades due to encroachment of woody plants (Appendix 1).
3.2.3 Vegetation Data Collection Procedures
Woody Density and Basal Area
For Site I, nine line transects and for Site II eight line transects of 400 m long and 10 m wide
were stretched at different points randomly as sampling units for woody vegetation density and
basal area measurement. Then in each transect line, the first 10 X 10 m plots were established at
30 meter, this point was selected randomly (using the lottery method for randomization) as
indicated by NARSC (1999) from the starting point of each line transect. The subsequent three
plots were established at constant intervals of 100 meters (systematic sampling) (NARSC, 1999).
Thus, a total of 68 plots in both sites (36 plots in site I and 32 plots in site II) were used.
In each plot, plants with diameter at breast height (1.4 m) ≥ 5 cm was recorded as matured plant
and plants with DBH < 5 cm were recorded as saplings (Gemedo et al., 2006). All rooted live
woody plants were counted regardless of being single-stemmed or multi-stemmed, and used for
an estimate of woody vegetation density per hectare. The data were expressed as relative and
absolute density.
Density for matured woody plants and woody saplings were calculated (equation 1, 2, and 3) and
expressed as total density, relative density and absolute density.
(1)
RELATIVE DENSITY: * 100 (2)
26
ABSOLUTE DENSITY OF A SPECIES
= * TOTAL DENSITY OF ALL SPECIES (3)
Woody Canopy Cover
For woody canopy cover measurement a total of 14 (seven transects in each ecological site) with
a length of 100 meter were used and data recorded by line intercept method. These transects were
also part of the long transects (400 m) used for woody density and basal area measurements.
Along the transect line, the horizontal linear length of each plant that intercepts the line at the
vertical projection of each plant canopy were measured as described in NARSC (1999).
Woody Species Composition and Similarity of Species
Woody species composition was derived from the relative density of each species. Percent
composition was calculated by dividing the total number for each plant species by the total
number for all plant species (NARSC, 1999).
Similarity of sites in their species composition was compared using Morisita‟s similarity index
(IM) (equation 4). The probability of drawing an individual species randomly from area „x’ is the
same as drawing the same individual species randomly from area „y’ is unaffected by sample
size; this index, called Morisita‟s index. The sampling mean of Morisita‟s index is unaffected by
sample size, while the variance decreases steadily with increased sample size (Joshua and Helene,
2002). Therefore, this index was calculated to assess the similarity in species composition
between the two sites. The coefficient has a value from 0 to 1, where 1 reveals complete
similarity and 0 complete dissimilarity.
27
Morisita’s Index of Similarity (IM):
(4)
Where: l 1 & 2 are diversity index of site I and II
Im = Morisita‟s index of similarity
l1 and l2 are given as Simpson Index of Diversity:
la = (5)
ni = number of individuals for each species in plots
Xi = number of a species in the first sample or site I
Yi = number of a species in the second sample or site II
Na = total number of species in the sample of site I or site II
Woody Vegetation Diversity, Evenness and Importance value Index
The following indices were derived from the vegetation data. Species diversity using Shannon-
Weiner diversity index (H‟) (equation 6), and evenness or equitability (J) (equation 7) was
calculated to determine the ecological sites health (Kent and Coker, 1996).
Shannon-Weiner Diversity Index (H’) = (6)
Where: Pi = the proportion of individuals or the abundance of the ith
species expressed as
a proportion of total number of species in each site or transect
ln = log base 10
Equitability (evenness) = (J) = H‟/H‟max = (7)
28
Where: s = the number of species in each site or transect
Pi = the proportion of individuals or the abundance of the ith
species expressed as a
proportion of total number of species in each site or transect
ln = log base 10
Importance Value Index (IVI) of woody plants in both sites were computed from data collected
for density, basal area and from frequency counts (equation 8) to identify the extent of the
dominance, occurrence and abundance of a given species in relation to other associated species in
each site. It is also important to compare the ecological significance of a given species (Kent and
Coker, 1996).
Importance Value Index (IVI) of a Species
= Relative density + Relative dominance + Relative frequency (8)
Relative density (equation 2) and frequency was calculated and expressed as total frequency and
relative frequency of a species (equation 9 and 10) for matured woody plants.
FREQUENCY = * 100 (9)
RELATIVE FREQUENCY: * 100 (10)
Measurements of diameter at breast height (DBH) for matured woody plants were converted to
basal area of individual plant using equation 11. Sum of basal areas of each species in each
transect were computed using equation 12. Then the average basal areas of each species (equation
13) in each transect line was calculated and used to determine the absolute and relative
dominance of species in a site (equations 14 & 15).
29
BASAL AREA OF INDIVIDUAL PLANT = (11)
Where: d = diameter at breast height & = pi (3.141592…)
BASAL AREA OF A SPECIES = Sum of basal areas (12)
AVERAGE BASAL AREA OF A SPECIES: (13)
ABSOLUTE DOMINANCE (PER UNIT AREA) OF A SPECIES
= Absolute density of a species * average basal area of a species (14)
RELATIVE DOMINANCE = * 100 (17)
3.3 Data Analysis
Descriptive statistics to express responses, ranking index and cross-tabulation and chi-square test
were used to analyze socio-economic survey data.
An index was calculated to provide overall ranking, on perception on causes of rangeland
condition change, encroaching woody plants and livestock production constraints, using
preference-ranking methods (equation 18). In preference ranking method, index was computed
with the principle of weighted average and indexes were ranked each other using auto ranking
with MS- excel 2007.
The following formula was used to compute index:
Index = Rn * C1+ Rn - 1 * C2…. + R1* Cn / Σ Rn * C1+ Rn - 1 * C2…. + R1* Cn (18)
Where:
Rn = Value given for the least ranked level (example if the least rank is 5th
, then Rn = 5, Rn - 1 =
4, R1 = 1)
30
Cn = Counts of the least ranked level (in the above example, the count of the 5th
rank = Cn, and
the count of the 1st
rank = C1).
The responses of pastoralists (such as perception on their rangeland condition, the contribution of
absence of fire for encroachment, feed availability, pattern and frequency of mobility, income
diversification activity, household income, herd composition, food security and attitude towards
agro-pastoralism) from the two sites were tested for the hypothesis of no difference between sites
by cross-tabulation and chi-square test using Minitab 14 (Minitab, 2003). Significant differences
were detected at P ≤ 0.05.
The model for the socioeconomic study (simple comparative assessment) with complete
randomization was:
yij = μ + τi + εij (19)
Where:
yij is the total response for site i, sample point j (i.e. j: respondent or household);
μ is the overall mean;
τi is ith treatment (site) effect
εij is the residual random error associated with the ijth
observation.
The model for the vegetation measurement (simple comparative experiments) with complete
randomization was:
yij = μ + τi + εij (20)
Where:
31
yij is the measured attribute (for all species combined or for a single target species) for
site i, sample point j (i.e. j: transect or quadrate);
μ is the overall mean;
τi is ith treatment (site) effect
εij is the residual random error associated with the ijth
observation.
First, the density data tested for normal distribution by Anderson‟s test for normality using
MINITAB 14 (Minitab, 2003). Woody plants density in site I and site II were tested for
encroachment (μ0 ≥ 2,500 plants/ha) by one sample t test (one tail directional test), since, the
threshold density for encroachment is 2,500 plants per hectare (Roques et al., 2001; and Richter
et al., 2001).
Two independent samples non-parametric test were used to compare the following attribute
difference among sites. Total density (N/ha) of woody plants, density of saplings, total canopy
cover (%), diversity of species, species evenness, were compared between sites by Mann-
Whitney U test using MINITAB 14 (Minitab, 2003) since the sample data from each site don‟t
have equal variance.
Cross tabulation and chi-square test were also employed for species composition (%), relative
dominance of species (%) and Importance Value Index (IVI) of each species, to see whether there
was an association between the attributes and sites or not, using Minitab 14 (Minitab, 2003).
Significant differences were detected at P ≤ 0.05.
32
Chapter IV: Results and Discussion
4.1 Socio-economic Survey
4.1.1 Perception of Pastoralists on Rangeland Degradation and Encroachment
The result of this study shows that 77.5%, 22.5% and none of respondents the condition of their
rangeland as being in poor, fair and good condition, respectively in site I (the encroached site). in
site II (the unencroached site) 45%, 22.5% and 32.5% of respondents reported the condition of
their rangeland as being in good (even though some changes had been observed in the past few
decades), fair and poor condition, respectively (Pearson Chi-Square = 25.4; P = 0.000).
(Appendix 2).
Based on their view, the major causes for change in rangeland condition were drought,
encroachment, and poor rangeland management in site I. While in site II drought, poor rangeland
management, and over grazing were the main causes of vegetation cover change (Table 1). The
deterioration of the herbaceous layer in site I caused higher rate of migration of livestock to the
rangelands of site II. This increment in livestock in site II caused much of the rangeland condition
deterioration besides the other causes of changes.
Table 1. Causes of change in rangeland condition in encroached and unencroached sites in Telalak
woreda as ranked by respondents.
Causes of change Site I (N=40) Site II (N=40)
Rank Index Rank Index
Drought 1 0.31 1 0.32
Over grazing 4 0.14 3 0.22
Looping & clearing 5 0.11 4 0.12
Encroachment 2 0.25 5 0.11
Poor rangeland management (lack of
fire, rotational grazing & restricted access)
3 0.2 2 0.25
N.B. Site I represent the encroached site & Site II represent the unencroached site.
33
Gemedo (2004) in Borana rangelands, southern Ethiopia, also documented the contribution of
drought and over grazing for rangeland deterioration. Coppock (1993) also indicated sites that
endured heavy grazing pressure found with high densities of very young woody plants and low
rangeland condition, in Borana Rangelands, in southern Ethiopia.
According to the information obtained during the group discussions with the elders and as most
of the sampled households indicated, communal rangeland management (where the rangelands an
d their use are managed by clan leaders) was the one that was widely practiced in both sites. Most
of the respondents in both sites sensed the negative impact of open access rangeland management
as one of the contributing factors to the deterioration of rangelands condition.
Admasu (2006) indicated that Benna pastoralists in southern Ethiopia perceived the negative
effect of communal ownership of rangelands. The disadvantage of communal management is also
sustained by other studies (Oba, 1998; and Ayana, 1999). The problem is no one was taking care
of the communal land and even if, there did exists traditional grazing land management practice;
it was very weak as indicated by most of the respondents. Yayneshet and Kelemework (2004)
also indicated the ineffectiveness of the current traditional rangeland management system in
pastoral areas to overcome and reverse the deteriorating pastoral natural resources in north Afar,
Ethiopia.
The invasion of Parthenium hysterophorus on the rangeland of both sites and its negative effect
on other herbaceous species, was indicted by the majority of respondents (100% in site I and
72.5% in site II) (Pearson Chi-Square = 12.8; P = 0.000) (Appendix 2). According to elders in the
study sites, the herbaceous layer was very much destroyed over the last 10 to 20 years and
replaced with unpalatable forbs mainly Parthenium hysterophorus. The participants of group
34
discussion also agreed that the proportion of herbaceous to woody vegetation on their rangelands
has been declining.
All (100%) respondents of both sites recognized the presence of encroaching woody plants
(Acacia species) in their rangelands. The inhabitants of the area were aware that shrub/ bush
cover has escalated and shrub/ bush encroachment is becoming the major concern and threatening
their livelihood. Respondents in both sites mentioned Acacia mellifera and Acacia senegal are the
main encroaching woody plants in their rangelands and ranked first and second, respectively
(Table 2).
Table 2. Major encroaching woody plant species in encroached and unencroached sites in Telalak
woreda as ranked by respondents.
Species Site I (N=40) Site II (N=40)
Rank Index Rank Index
Acacia mellifera 1 0.41 1 0.31
Acacia senegal 2 0.37 2 0.28
Acacia nubica 3 0.11 3 0.23
Acacia horridae 3 0.11 4 0.18
These responses were also in agreement with the vegetation data (density, species composition,
cover, IVI and relative dominance values of these species were superior). Even though, the extent
of the expansion of these acacia species is not a problem at present time in site II, when we look
the density of saplings of these acacia species, in the future, if some management action is not
taken, it is anticipated that encroachment also occur in this site. The encroachment of rangelands
by species of Acacia has been reported in a number of different countries (Abule et al., 2007).
35
Livestock movement in search of food and water may also contribute for the dispersal of seeds of
different woody plants. The introduction of camel rearing in recent years as coping mechanism
for drought and woody plant encroachment contributed for the introduction and spreading of
encroaching Acacia species in site II rangelands. According to the informants, while the camels
browse on Acacia encroaching species, their seeds did not digested but released through faeces
and then regenerate again in mass. Thus, these species were believed to have been distributed
with the expansion of camel to the rangelands of both sites.
Most of the respondents, 90% from site I and 60% from site II, agree on the contribution of the
absence of use of fire for encroachment (Pearson Chi-Square = 9.6; P = 0.002) (Appendix 2). The
presence of insufficient fuel, since drought and over grazing had reduced the grass layer in both
sites to sustain fire; and the use of fire for managing their grazing land had reduced. This was in
agreement with Gemedo et al. (2006) which indicated the need of occasional fires on grasslands
to regenerate, and to prevent establishment of bush seedlings. Ward (2005) also reported bush
encroachment occurs in many arid regions where fuel loads are insufficient for fires to be an
important causal factor.
For the occurrence of bush encroachment, several new hypotheses have been put forward to
explain tree-grass coexistence. Disturbances have been mooted as major determinants such as
human impact, herbivory, or drought, and spatial heterogeneities in water, nutrient, and seed
distribution (Ward, 2005). Climatic factors such as shortage of rain, extended dry period and
frequently occurring drought have resulted in low herbaceous cover and favored the expansion of
encroaching Acacia species (Gemedo, 2004). Rainfall amount and frequency, coupled with
specific soil nutrient levels, may drive this phenomenon (Ward, 2005). Interestingly, global
36
climate change may also create bush encroachment. Current trends in atmospheric CO2
enrichment may exacerbate shifts from grass to woody plant domination (Ward, 2005).
4.1.2 Pastoralists Adaptation to Woody Plants Expansion
Pastoralists have developed strategies as internal response to the conditions of growing food
insecurity because of vegetation cover change mainly bush encroachment. The first strategy was
diversifying their food and income source. Pastoralists in site I, begun to diversify their income
and dietary source by cultivating crops. The agro-pastoralists in both sites argued that, the
quantity of crops they produced was small and could not be sufficient for a year. However, they
indicated that cultivation could fill the gap of food deficit they experience for many months
during the year. Besides, they used crop residues and crop aftermath as a source of dry season
feed for animals. Following increased deterioration of food security situation of the Afar due to
recurrent droughts and the subsequent vegetation cover change the need to cultivate rangelands
and participating in other livelihood strategies had been observed in northern Afar pastoralists
(Yayneshet and Kelemework, 2004).
According to the informants, the other strategy to adapt the vegetation cover change was
changing their herd structure. In both study sites pastoralists had more than one species of animal
especially goat, and camels. Since, herd management is the principal means of sustaining
livelihoods, this multi-species composition of the livestock holding has the advantage of utilizing
both browse and herbaceous species in the rangelands, and hence can provide a continues supply
of human food.
Change in herd size and composition to satisfy the maintenance requirements of a pastoral
household were also reported by Yayneshet and Kelemework (2004) in north Afar Pastoralists
37
because of change in vegetation cover. Borana pastoralists (Adisu, 2009) in southern Ethiopia
also employed the practice of change of herd structure through the introduction of camel
husbandry, as well as, rearing more goats than before.
Private ownership of grazing lands has been also reported as strategy during group discussion.
Since communal management of rangelands is eroding and unable to control the use of rangeland
resources, preparation and use of grazing reserve on personal level increased. Pastoralists in both
sites started fencing grazing areas as enclosures individually for dry season grazing. However, the
introduction of privately owned grazing reserve could aggravate rangeland degradation through
shrinking grazing land. The result was also in agreement with Yayneshet and Kelemework
(2004), who indicated large proportion of communal prime grazing land, had been individualized
following vegetation cover change in northern Afar. Similar situation was also reported in Borana
rangeland (Adisu, 2009); even though resource use is largely communal, private enclosures
appear increasing in the recent past decades as strategic response to rangeland productivity
reduction due to encroachment.
The pastoralists during group discussion also indicated, mobility was the other strategy used to
adapt the vegetation cover change. However, time and duration of migration during the dry
periods of the year was different in the two study sites. Migration for long period of time was the
only means for the pastorals in site I, while in site II as the condition of the rangeland is relatively
better, only part of their animals migrates during the late dry periods (May – June). Mobility
characterizes the pastoral production system. It is a very important strategy of pastoralists to
38
exploit scarce vegetation and water resources in dry lands and it is in harmony with the harsh
environment.
4.1.3 Consequences of Woody Plants Expansion on the Socio-economic Transformation of
Pastoral Livelihoods
4.1.3.1 Change in Pattern and Frequency of Mobility
The entire respondents of both sites mentioned that migration was part of their livelihood, but the
kind of migration was different. Mobility pattern of pastoralists was different between the sites
(Pearson Chi-Square = 9.108; P = 0.011) (Appendix 2) and it was closely related to their
rangeland situation. In site I, 20% and in site II none of the respondents were nomads, that they
did not have permanent settlement areas and they move with their livestock wherever there was
forage. 60% of the respondents in site I and 70% of respondents in site II followed a transhumant
way of life, a condition where they had permanent settlement areas but in dry periods, their
livestock with the herders move seasonally in search of feed and water. Sedentary way of life was
also different in the two sites, where by 20% and 30% of the respondents practiced. These
respondents were agro-pastoralist and pastoralists that live near Telalak, Wata and Awash Rivers.
Generally, pastoralist of site I were mainly transhumant and nomadic. However, in site II,
transhumance was the major mobility pattern. Usually there was a cross-regional migration and
their migration root as indicated by the respondents was to Megenta kebele in site II adjacent to
Awash River, to the Alledagie plains in Gewane woreda and in extreme cases to Dawa chefa in
Amhara National Regional State.
The majority (60%) of the respondents in both sites agreed that the frequency of migration has
been increasing because of deterioration of grazing land especially the herbaceous vegetation
39
cover (Pearson Chi-Square = 19.2; P = 0.000) (Appendix 2). However, perception towards the
contribution of encroachment for migration was quite different in the two sites. Only 10% of
respondents in site II explained there was contribution of encroachment for migration. However,
in site I, 70% of the respondents replied it does contribute (Pearson Chi-Square = 30.0; P =
0.000) (Appendix 2). Bush encroachment had greatly affected the feed availability for livestock
mainly in site I that make the pastoralists of the site more mobile in search of feed than
pastoralists in site II. Yayneshet and Kelemework (2004) also reported similar situation in
northern Afar, which indicate, traditional pastoral strategies related to natural resource
management and use have been eroded and disrupted such as mobility (time, duration and
frequency of movement) and resulted in pastoral socio-economic transformation. Niguse (2008)
in Borana rangelands, in southern Ethiopia and Amaha (2006) in Somali rangelands, in eastern
Ethiopia, reported increased frequency of migration in search of feed and water due to the effect
of bush encroachment.
4.1.3.2 Frequency and Causes of Conflict
All respondents in site I revealed that there has been a conflict arising from grazing land use and
shortage of feed resource following the deterioration of rangeland condition due to encroachment.
Encroachment had resulted in an increased frequency of mobility of pastoralists to neighboring
areas in search of feed for their livestock. Elders in site I described the causes of conflict at
present time were water, grazing land and livestock raiding. However, before 30 years the main
cause of conflict between neighboring pastoralists were cattle raiding. However, in site II the
main cause of conflict was cattle raiding.
40
Conflict on the use of grazing land might often occur in most pastoral areas. Study by WARC-
APARI (2007) also indicated the occurrence of conflict between southwestern pastoralists and
pastoralists of neighboring areas in the past two decades had been increased for use of the same
resource (grazing land). Yayneshet and Kelemework (2004) indicated changes in natural resource
use in Afar territory have had negative implications for the pastoral mode of production and
culminated in resource use conflict. Similarly, Alemayehu (1998) and Adisu (2009) indicated
encroachment has resulted in frequent conflict due to shortage of grazing resources in Borana
rangelands, in southern Ethiopia.
According to elders during group discussion, frequency of conflict was higher before the last
decade in both sites, even though the causes were different between sites. However, in the past 10
years occurrence of conflict had been declined. The possible reason for this was conflicts
between other ethnic groups were solved in customary/ traditional courts and administrative
bodies. In both study sites inter-clan marriage and agreement between different sub-clan leaders
was the main strategy to avoid and resolve conflicts. The preventive measures that were taken to
avoid conflicts between ethnic groups were building adjacent neighboring woredas and zone
administrative conflict resolution committee. As described by all of respondents of site I, and
Telalak woreda administrative and security office, this committee has brought a great reduction
on conflict occurrence by addressing issues of local conflict over resources and by allowing
temporary access of livestock to outsider grazing land like Cheffa valley in Amhara National
Regional State.
41
4.1.3.3 Effect on Livestock Production
The respondents of the study area had ranked woody plants encroachment (third in site I and fifth
in site II) and the associated shortage of feed to livestock (first & second in site I and II,
respectively) were the major constraints for livestock production in the study area (Table 3).
Encroachment of woody plants had affected the livestock production of study area in two ways.
First, by decreasing the rangeland productivity and grass availability that results a decrease in
herbaceous biomass production. Secondly, it restrict the movement of livestock and makes
understory herbaceous plants inaccessible for grazing.
Table 3. Livestock production constraints in encroached and unencroached sites in Telalak woreda.
Constraints Site I (N=40) Site II (N=40)
Index Rank Index Rank
Feed shortage 0.23 1 0.235 2
Livestock disease 0.07 6 0.12 4
Re-current drought 0.23 1 0.24 1
Shortage of water 0.09 5 0.16 6
Market problem 0.06 7 0.04 7
Conflict 0.11 4 0.098 3
Encroachment 0.19 3 0.106 5
The result was in agreement with Coppock (1993), Gemedo et al, (2006) and Melesse (2003)
who reported reduction in biomass production, herbivores access restriction to understory grass
and restriction of easy movement of animals because of encroachment of woody plants, in the
southern rangelands of Borana. Encroachment of woody plants is continuously threatening the
pastoral production and challenging the sustainability of livestock (Solomon et al., 2008), and as
indicated by Philpott et al. (2005) Afar rangeland is no longer able to sustainably support cattle
production. According to Solomon et al, (2008), an increase in bush cover by 10% reduces
grazing by 7% and 90% bush cover eliminates grazing completely.
42
Majority of the respondents in both sites (87.5% in site I and 60% in site II) agreed on the effect
of vegetation cover change on feed availability for livestock (Pearson Chi-Square = 7.8; P =
0.005) (Appendix 2). However, the effect of vegetation cover change on feed availability for
livestock was higher in site I than site II. Use of feed resources by respondents in the two sites
was almost similar, except the difference in their grass and herbs usage and crop residue usage.
Pastoralists in site II have relatively better grass use than Site I pastoralists. However, all the
respondents in both sites agreed that there was a critical feed shortage during part of year.
Herbaceous plants (grasses and legumes) can sustain animals for only one month in site I and up
to 3 months in site II; after that, pastoralists were forced to migrate to other areas.
Similar situation were also observed in the rangelands of Borana, southern Ethiopia (Alemayehu,
1998; and Adisu, 2009). The result was in agreement with Oba (1998), who reported the presence
of critical cattle feed shortage assumed to be caused by rangeland degradation that is
characterized by invasion of undesirable woody species and unpalatable forbs, and losses of grass
layer in the Borana rangeland. Melesse (2003) also reported the effect of bush encroachment on
rangeland productivity, in terms of botanical composition and forage productivity (feed
availability) in Borana rangelands, southern Ethiopia.
According to elders during group discussion, milk production in present days has generally
reduced as compared to the past times (20 and 30 years back). However, they also indicated, the
present time milk production in site II was relatively higher than site I. This might be due to the
relatively higher number of cattle owned by respondents in site II, and relatively better situation
of the rangeland in site II with relatively better-feed availability to feed their cattle.
Encroachment have resulted in destabilization of the range system which is manifested by a
reduction of milk and meat production per animal, retarded growth of calves, loss of resistance to
43
disease, and decreased herd size. Woody plant encroachment in site I, had affected pastoralists by
decreasing livestock production (in quality and quantity) and resulted in food insecurities. The
result was in agreement with Alemayehu (1998) and Adisu (2009) which reported encroachment
resulted reduction of milk and meat production per animal in Borana rangelands, in southern
Ethiopia.
In Borana rangelands, southern Ethiopia, Gemedo et al. (2006) found encroachment of woody
plants has decreased rangeland and grass availability, which resulted decrease in herbaceous
biomass production and the livestock production was affected. As described by Ward (2005),
bush encroachment is one of the major structural problems limiting optimum animal production
particularly from the grazer point of view. Bush encroachment reduces the carrying capacity for
livestock. The reduction in carrying capacity is of great significance because these lands contain
many pastoralists whose livelihood is threatened by this process.
3.1.3.4 Effect on Household Income
Response of sampled household (72.5% and 47.5% in site I and site II, respectively) indicated
their income had decreased (Pearson Chi-Square = 20.333; P = 0.000) (Appendix 2). This was
due to the direct or indirect effect of vegetation cover change (due to encroachment in site I; and
deteriorating grazing land condition in site II) on livestock productivity and survival. Amaha
(2006) also indicated the presence of economical stress (decline in pastoralists‟ income) on
pastoralists because of woody plant encroachment in Somali, eastern Ethiopia pastoralists.
As internal response to the conditions of growing food insecurity due to the effect of vegetation
cover change, pastoralists (35% in site I and 20% in site II) begun to diversify their income and
dietary needs by cultivating crop, working as civil servants and trading. There was no enough
44
evidence of association (Pearson Chi-Square = 2.257; P = 0.133) between income diversifying
activities and sites (Appendix 2). The result indicates income diversification activity was not
different in site I and site II. In both sites, respondents described the need to diversify livelihood
sources from crop cultivation and other activities due to diminished rangeland productivity and
increased degradation. The livestock sector alone could not meet all the dietary and economic
needs of pastoralists. The result was in line with Adisu (2009), many Borana households depend
on additional sources of income and can no longer survive on cattle based pastoralism in response
to bush encroachment either to reduce adverse effect or to take opportunity of it.
4.1.3.5 Effect on Composition of Herd
The association between the sites and the observed household herd composition was strong
(Pearson Chi-Square = 825.319; P = 0.000) (Appendix 2). The household herd composition of
respondents in the two sites was different. The main component of the herd of pastoralists in site
I was goat (83.3%), camel (10.2%), and 1.4% (cattle), 4.7% (sheep) and 0.5% (equines). In site
II relatively better diversification of herd components was seen with 59%, 29.2%, 5.5%, 6.2%
and 0.15% goat, sheep, cattle, camel and equines, respectively. However, cattle proportion was
low in both sites, which were the main source of milk, and small ruminants mainly goat shows
higher proportion in herds on both sites. Most of the pastoralists of site I shifted their stock to
goat and camel (browsers) because of the decreased grass cover as a result of bush encroachment.
Change in herd size and composition to satisfy the maintenance requirements of a pastoral
household were also reported in north Afar Pastoralists because of change in vegetation cover
(Yayneshet and Kelemework, 2004).
45
It was explained by the elders of study woreda, during the group discussions, the relatively higher
proportion of goats is because they are adaptable in their feeding habits and their ability to utilize
a wide range of plants and plant parts. Following the occurrence of bush encroachment the
practice of herd diversification through the introduction of camel husbandry, as well as, rearing
more shots than before in Borana pastoralists, in southern Ethiopia was also reported by Adisu
(2009). Amaha (2006) also reported, in Somali rangelands in eastern Ethiopia, as encroachment
by woody plants increased and grasslands have shrunk resulting in changes in the original species
composition of livestock in favor of camels and small ruminants. The species composition of
livestock holding per household changed with camels increasing in number, whereas the numbers
of cattle and donkeys declined.
4.1.3.6 Effect on Food Security and Attitude towards Agro-pastoralism
This study also assessed food insecurity and dependency of the society on food-aid from the
perception of the sampled households. Majority of respondents (75%) in site I replied food
insecurity and dependency on food-aid status in their site was high; and 45% of the respondents
in site II replied condition of food insecurity and dependency was moderate (Pearson Chi-Square
= 11.818; P = 0.003) (Appendix 2). Site I was mere dependent and food unsecured than site II.
The respondents also indicated the food insecurity and dependency on food-aid was much related
to bush encroachment in site I, and deterioration of rangeland condition in site II. With the
decline of grazing due to encroachment, coupled with recurrent droughts, people in the study area
became highly food insecure and dependent on government food aid for their survival. In highly
invaded areas people are now reliant on food aid on average for 5-6 months in good years and for
up to 10 months in drought times (PCDP, 2005). The ultimate effect of bush encroachment in
46
Borana rangelands in southern Ethiopia, as reported by Adisu (2009), was food insecurity and
dependence on external food aid of the Borana pastoralists.
In both sites, pastoralists who did not yet practiced cultivation showed deep interest (70% and
64.5% in site I and II, respectively), in cultivation. There was no enough evidence of association
(Pearson Chi-Square = 0.203; P = 0.653) between attitude towards cultivation practice and sites
(Appendix 2). There positive attitude towards agro-pastoralism was almost equal in both sites.
This was in agreement with research result by Yayneshet and Kelemework (2004) which
indicated, following the increased deterioration of food security situation of the Afar due to
recurrent droughts and vegetation cover change the need to cultivate rangelands had been
increased. This growing interest in cultivation among the pastoral and agro-pastoral people,
following woody plants encroachment and the subsequent grazing land deterioration, was also
reported in studies (Solomon, 2000; Admasu, 2006) conducted in Borana rangelands, southern
Ethiopia. However, supporting cultivation need to be based on mutual consultation and land use
principles and should consider longer-term ecological and social costs.
4.2 Woody Vegetation Attributes
4.2.1 Woody Species Composition and Similarity
Species composition of most of woody plants was significantly different between site I and site II
(Table 5). Acacia mellifera and Acacia senegal attained relatively high values of abundance in site
I. Acacia mellifera, Acacia tortilis, Salvadora persica, Acacia nilotica and Acacia senegal
attained relatively high values of abundance in site II (Table 4). The higher species composition that
was shared by only two species in site I could be due to the heavy grazing that removed the grasses
layer, freeing up water and soil resources for the shrubs to exploit; in addition, the soil property
47
of the sites could attributed for the difference. However, the composition of species in site II was
diverse and the site was relatively composed of other woody species in better proportion. The
idea was also in agreement with Coppock (1993) and Tefera et al. (2006), which indicated sites
that endured heavy grazing pressure found with lower species composition of woody plants in
Borana Rangelands in southern Ethiopia.
Table 4. Woody vegetation species composition in encroached and unencroached sites in Telalak woreda
in Afar region.
Species Species composition (%)
P Site I Site II
Acacia mellifera 50.96 12.36 0.000*
Acacia senegal 37.34 7.02 0.000*
Salvadora persica 1.56 10.67 0.000*
Grewia ferruginea 2.49 3.93 0.000*
Acacia tortilis 0.83 11.24 0.000*
Acacia nubica 1.44 3.37 0.000*
Acacia nilotica 0.94 10.67 0.000*
Boscia coriaceae 1.37 1.69 0.000*
Cadaba rotundifolia 1.58 6.18 0.000*
Balanites aegyptiaca 0.21 5.06 0.000*
Acacia horridae 0.32 3.65 0.008*
Dodonea angustifolia 0.32 2.53 > 0.05n
Ficus sycomorus 0.32 6.74 0.000*
Grewia villosa 0.21 2.53 0.000*
Zizyphus mauritiana 0.11 1.69 0.000*
N.B: * The respective species in the two sites are significantly different (P<0.05).
The other possible reason for lower species composition in both sites could be reduced fire fuel
that was necessary to sustain wild fire or use of fire by pastoralists for the management of woody
vegetation. This was in agreement with Gemedo et al. (2006) and Solomon et al. (2007), reported
absence of fire was the major factor that for woody plants invasion on rangelands of Borana.
Another possible reason could be the higher competitive ability of these two species contributes for
their dominance. These all factors could be the possible reasons for the formation of distinct cohorts
48
of shrubs of similar size and presumably age in site I. Acacia shrub seeds were able to germinate
en masse, creating an impenetrable thicket as described by Britz and Ward (2007) and de Leeuw
et al. (2001). However, the shared abundance by other species (A. tortilis, S. persica and A.
nilotica) in site II, may be due to lower grazing pressure during the time when the invasion
started (as explained by elders during group discussion), better herbaceous layer (better
competition ability with shrubs), and the soil nature may prevent the domination of the site by
single species of shrub.
Each species showed remarkable differences between the different rangeland sites and species
composition in site I was very low as compared to site II (Appendix 7). The reasons that might be
suggested as causes for the result are the dominance of A. mellifera and A. senegal in site I may
create loss of ecosystem heterogeneity and negatively affect the other native species of the vegetation
community. The observed situation was also in agreement with the idea of Dougill and Cox (1997)
and Riginos and Young (2007), which indicate „„Woody‟‟ or „„bush‟‟ encroachment can have
profound negative consequences for native fauna and rangeland productivity. Britz and Ward
(2007) also indicated when bush encroachment occurred; virtually impenetrable thickets of a
single species replaced multi-species open savannas. The negative effect of the invasion of
Acacia species on botanical composition and biodiversity loss of rangelands was also reported by
Melesse (2003) in Borana, southern Ethiopia.
Morisita‟s index of similarity or index of overlap (IM) of the fifteen woody species (that were
found on both sites) between site I and site II was 0.397. This indicates there was less woody
plant species similarity between site I and site II, and the two sites had only 39.7% of species in
common. According to Kent and Coker (1996), similarity indices measure the degree to which
49
the species composition of sites or sample matches is alike. Moreover, it can be used to look the
degree of association between species and the level of similarity between sites or samples.
4.2.2 Woody species density
The average matured woody species density values were 2636.11 ± 66.16 in Site I and 1112.5 ±
32.39 plants/ha in Site II. The results shows total density of woody plants was significantly
different (W = 117.0; P = 0.0003) between the two sites and the mean density value of matured
woody plants in site I were 2.4 times that of Site II (Table 5).
Following the view of Roquest et al. (2001), Richter et al (2001) and Gemedo et al. (2006), site I
woody plants density has crossed the critical threshold and appears to be encroached, but site II
had significantly lower density of overall woody plants and seems not encroached. Admasu
(2006) reported that in the communal grazing areas of Benna-Tsemay district, south Omo zone,
woody vegetation density per hectare greater than 2,500 was encroached. Similar result was also
found in the rangelands of Borena, southern Ethiopia, with woody plant density of 3014 plants
per ha were considered as crossed the critical threshold level and entered into the encroached
condition (Gemedo et al., 2006). Teshome et al. (2009) reported woody species density of 2454.9
plants/ha, was on the border between encroached and non- encroached condition in Bale zone,
southern Ethiopia. In addition, in southern Ethiopia, Ayana and Oba (2007) reported that woody
species density 3995 stems per ha was estimated in encroached rangeland.
The effect of woody plants with density beyond critical limit is that they decrease herbaceous
production and grazing capacity of rangelands mainly due to severe competition for available soil
water. This is particularly pertinent in Acacia mellifera encroached system, as the lateral roots of
this species are known to extend with the grass rooting zone and it is noted for its high water use
50
(Niguse ,2008). Beside their valuable contribution as browse feed resource, woody plant with
high density had negatively affect the pastoral production from grazing point of view. The better
herbaceous cover in site II could be due to the lower density of woody plants density.
Table 5. Average total density (N/ha), saplings density (N/ha) and canopy cover (%) of woody plant
species in encroached and unencroached sites in Telalak Woreda in Afar region (Mean ± SE).
Vegetation attributes Sites
P Site I Site II
Total woody species density 2636.11 ± 66.16 1112.5 ± 32.39 0.0003*
Woody plant saplings density 744.4 ± 89.4 443.8 ± 65.1 0.0193*
Woody species canopy Cover 68.1 ± 11.4 42.06 ± 5.25 0.0149*
N.B. *: Attributes of woody plants in the two sites are significantly different (P<0.05).
The mean value was calculated from the 9 and 8 transects for Site I and Site II, respectively.
The mean density of woody plant saplings was 744.4 ± 89.4 plants/ha in Site I, and 443.3 ± 65.1
plants/ha in site II (Table 5). The results shows density of woody plants saplings was
significantly different (W = 103.0; P = 0.0193) between the two sites. The result of this study
showed, even though sapling density differ significantly between sites it was much lower than
other sapling density results from encroached rangelands of Borana. In Borana rangelands,
Niguse (2008) reported the density of saplings in open grazed rangelands was 4065 per hectare,
and Ayana and Oba (2007) reported density of saplings in open grazed rangelands was 1858 per
hectare. The observed lower sapling density could probably link to factors that influence woody
plant seed germination in the open grazed areas. Heavy grazing could also reduce the
regeneration of woody plant density on both sites (Ayana and Oba, 2007).
By considering the density of saplings of woody species in both encroached and unencroached
sites the regeneration status of the woody plants in each site were examined. The number and
type of saplings in any vegetation shows the regeneration status of that vegetation (Dereje, 2006).
51
Three species contributed to 87.32% and 71.13% of the total sapling count in site I and site II,
respectively. These were G. ferruginea, A. mellifera and A. senegal in site I; and A. senegal, A.
tortilis and A. mellifera were species with highest density of the total regeneration in site II
(Table 6). The composition, distribution and density of saplings indicate the future status of the
vegetation (Niguse, 2008). Higher proportion of young plant (saplings) of these encroaching
Acacia species was observed in both encroached and non-encroached areas and this indicates the
encroachment continue as a threat to the productivity and sustainability of the rangelands in the
study area.
Table 6. Mean density of woody species saplings and their relative contribution to the total woody
species sapling density, in encroached and unencroached sites in Telalak woreda in Afar region.
Species Site I Site II
Density (N/ha) % contribution Density (N/ha) % contribution
Grewia ferruginea 1975 29.48% - -
Acacia tortilis 50 0.75% 950 26.76%
Acacia mellifera 1975 29.48% 400 11.27%
Acacia senegal 1900 28.36% 1175 33.1%
Balanites aegyptica 275 4.1% 275 -
Boscia coriaceae 100 1.49% - 7.75%
Grewia villosa 50 0.75% 75 2.11%
Cordia sinensis 100 1.49% - -
Acacia etbaica 75 1.12% 175 4.93%
Cadaba rotundifolia 125 1.87% - -
Acacia nilotica 75 1.12% 225 6.34%
Rhus natalensis - - 175 4.93%
Acacia nubica - - 100 2.82%
Total 6700 100% 3550 100%
The regeneration status shows that most the woody species that were dominant in encroached site
possessed high number of saplings in non-encroached. This high number of saplings may indicate
52
that woody plant species that dominated the encroached site were continued to expand and
dominate the unencroached sites through seed germination. High number of saplings in the
already encroached sites also shows that density of the woody plant will increase in the future
and shrub/ bush thickening will continue as a major problem unless an appropriate solution is
taken.
4.2.3 Woody species canopy cover
Woody plant canopy cover was 68.1% ± 11.4 in site I and 42% ± 5.25 in site II. The result
showed that there was significant difference in canopy cover (W = 70; P = 0.0149) between site I
and site II (Table 5). Canopy cover > 40% is taken as an indication of encroachment (Roquest et
al, 2001; Richter et al, 2001; and Gemedo et al, 2006). Ayana (2005) also indicate rangelands
with shrub/ bush canopy cover more than 40% were considered as encroached. It was suggested
that, site I had considered was crossed the critical threshold level and entered into the encroached
condition.
However, in site II, only some woody plant species were noted to have higher mean percent
canopy cover and the canopy cover was contributed by many other species (Appendix 3.1). The
species with highest canopy cover in site I were Acacia senegal (31.61%) and Acacia mellifera
(23.14%). However, in site II, the total canopy cover was shared by mainly Acacia nubica
(8.0%), Acacia senegal (7.97%), Acacia tortilis (7.07%) and Acacia nilotica (5.14%). From this
it was possible to see the higher canopy cover (48.05% of the total canopy cover of woody
plants) in site II was contributed by non encroaching species (Acacia nubica, Acacia tortilis and
Acacia nilotica) and was not by the encroaching Acacia species (A. mellifera and A. senegal).
This could indicate encroachment by A. mellifera and A. senegal was not a threat in site II.
53
4.2.4 Woody species Diversity and Evenness
The study area was composed of mixed woody species dominated by Acacia, Grewia, Salvadora
and allied genera. A total of 20 woody species were encountered and recorded during sampling
period (Appendix 3.1). Fifteen species in site I and twenty species in site II were recorded;
among the 20 species, 15 species were recorded in both sites.
Shannon-Weaver index (H‟) of woody species in site I and II were 1.225 and 2.704 respectively
(Table 7). There was significant difference in diversity of species (W = 46.0; P= 0.0005) between
site I and site II. The diversity index of both sites were lower than woody species diversity
indexes that were reported for encroached (2.67) and unencroached sites (3.16) by Niguse (2008)
in Borana rangelands, in southern Ethiopia.
Table 7. Species diversity (H’) and evenness index (J) of woody plant species in encroached and
unencroached sites in Telalak Woreda in Afar region.
Index values Sites
P Site I Site II
Diversity index (H‟) 1.225 2.704 0.0005*
Evenness or equitability (J) 0.45 0.92 0.0006*
No of species 15 20
N.B. * The respective vegetation attributes in the two sites are significantly different (P<0.05).
The mean value was calculated from 9 & 8 transects for Site I and II, respectively.
It might be suggested that over grazing contributes for the lower diversity index on both sites.
The reduced woody species diversity value in site I implies the lower stability and function of the
rangeland ecosystem and lower specie interaction in the site. Which finally resulted lower
productivity of the rangelands were declined. The increased bush or shrub density adversely
influenced diversity, relative abundance and occurrence of other woody species and grass
species. Higher coverage of a particular species (A. mellifera and A. senegal) resulted in
54
decreased diversity index of site I. The same idea by Moleele et al. (2002) was also suggested
that the encroachers might monopolize soil moisture and nutrients preventing the original
vegetation from re-establishing. Consequently, the encroachment might result in the reduction in
carrying capacity for livestock production and lowering food security and nutrition as reported by
Kirwan et al. (2007). Therefore, encroachment is of great significance because this process
threatens the livelihood of southwestern Afar pastoralists.
Site I attained a species evenness index (J) of 0.45 and site II attained a species evenness index
(J) of 0.92. There was significant difference in species evenness (W = 46.0; P= 0.0005) between
site I and site II. This shows, site II had higher even distribution of woody species as compared to
site I (Table 7). The most probable reason for this difference between the two sites might be the
effect of encroaching acacia species and soil property, which influence the even distribution of
other woody species (Niguse, 2008). Lower species evenness or relative abundance of species in
could be the resulted because of encroachment (Adisu, 2009; Teshome et al., 2009). Lower
equitability or evenness is an indication of lower relative abundance or biomass among species
(Brian and Wayne, 2004). The lower evenness index of site I also indicate, the woody vegetation
community of the site contains a few dominant species and many species are relatively
uncommon (Teshome et al., 2009).
4.2.5 Encroaching woody plant species
The relative dominance and importance value index of most species showed remarkable
differences between the different rangeland sites (Appendix 7; Table 8). As can be shown in
Table 9, only two species had mean IVI > 15 and the rest 13 species had mean IVI < 15 in site I. In
site II, nine species had a mean IVI > 15 and the rest 11 species had a mean IVI <15. Kent and Coker
55
(1996) reported that species with the highest importance value index are referred to as dominants. In
site I, Acacia mellifera and Acacia senegal with mean IVI of 115.91 and 99.67, respectively were the
most important species with highest IVI and they were also the dominant species. In site II, the
most important species were Acacia tortilis, Salvadora persica, and Acacia nilotica with relatively
close mean IVI of 37.6, 35.5 and 33.1, respectively and were also the dominant species.
Table 8. Woody vegetation relative dominance and importance value index in encroached and
unencroached sites in Telalak woreda.
Species R. Dom. (%) IVI (%)
Site I Site II P Site I Site II P
Acacia mellifera 42.45 6.58 0.000* 115.91 27.64 0.000
*
Acacia senegal 39.82 8.18 0.000* 99.67 22.45 0.000
*
Salvadora persica 3.68 13.23 0.000* 12.74 35.50 0.000
*
Grewia ferruginea 1.95 2.87 < 0.05* 11.94 9.70 0.000
*
Acacia tortilis 2.27 17.68 0.000* 10.60 37.61 0.000
*
Acacia nubica 2.92 5.44 0.000* 9.36 13.16 0.000
*
Acacia nilotica 2.31 13.72 0.000* 8.25 33.09 0.000
*
Boscia coriaceae 1.15 0.65 0.000* 7.52 3.78 0.000
*
Cadaba rotundifolia 1.70 3.95 0.000* 5.78 15.92 0.000
*
Balanites aegyptiaca 0.60 3.35 0.000* 3.30 15.65 0.000
*
Acacia horridae 0.33 8.41 0.000* 3.15 16.41 0.000
*
Dodonea angustifolia 0.32 1.33 > 0.05n 3.13 6.75 0.003
*
Ficus sycomorus 0.30 3.72 0.000* 3.12 16.26 0.000
*
Grewia villosa 0.13 1.84 0.000* 2.84 8.72 0.000
*
Zizyphus mauritiana 0.08 1.08 0.002* 2.68 4.22 0.000
*
Acacia etbaica - 3.56 - - 10.72 -
Dobera glabra - 1.82 - - 9.26 -
Nicotiana glauca - 0.81 - - 6.23 -
Cadia purpurea - 1.06 - - 3.64 -
Calotropis procera - 0.72 - - 3.30 -
Total 100 100 300 300
N.B.: R. Dom. = Relative dominance; and IVI = importance value index of woody species.
* The respective species in the two sites are significantly different (P<0.05).
Importance value index often reflects the extent of the dominance, occurrence and abundance of a
given species in relation to other associated species in an area (Kent and Coker, 1996). The index
56
allows us to summarize vegetation characteristics and rank species for management and
conservation practices. Acacia mellifera and Acacia senegal were highly encroachers in site I.
However, in site II the most important species were Acacia tortilis, Salvadora persica, and Acacia
nilotica that were not encroachers.
The pastoralists also reported A. mellifera and A. senegal were the encroachers on their
rangelands. Acacia mellifera and Acacia senegal are well known to encroaching species and also
reported on other studies (Christiana, 2010; Moleele et al., 2002; Adissu, 2009), respectively. The
spreading of these species not only threatens biodiversity but also alter the soil-water structure
through hydraulic lift (Moleele et al., 2002).
57
Chapter V: Conclusions and Recommendations
The socio-economic survey result indicates rangeland degradation in the form of woody plant
encroachment in site I, and loss of herbaceous cover due to over grazing in site II, and invasion of
P. hysterophorus in both sites were the main problems in the rangeland of the study area.
Bush encroachment was recognized by pastoralists as one of the major threats to their livestock
production in site I. The expansion of A. senegal and A. mellifera became the pastoralists‟
concern in both sites. Absence of use of fire, weakening of traditional rangeland management
system and frequent drought were identified as the major causes of vegetation cover change in
study area. The current traditional rangeland management systems generally found to be
ineffective to overcome and reverse deteriorating pastoral natural resources. Therefore,
strengthening and empowering local institutions of natural resources management, approaches
that integrate indigenous and external knowledge in development planning and decision making
in the area should be implemented.
Encroachment resulted reduction of herbaceous forage production for livestock, progressive
degradation of range resource and poverty among the pastoral community. Pastoralists mainly in
site I made adjustment in their livelihoods in response to range destabilization due to bush
encroachment to reduce adverse effect or to take opportunity of it. Other strategies employed by
pastoralists were herd diversification, private ownership of grazing land, crop production and
migration for long period.
The socio-economic consequences of the expansion of woody plants on the livelihood of
pastoralists in site I and site II differed markedly. In site I, the pattern, duration and frequency of
migration had been changed. Frequency of conflict had been increased, livestock productivity
58
and income of households had been declined, many households become dependent on additional
sources of income and can no longer survive on cattle based pastoralism, dependency on relief
food aid and food insecurity had been increased. The progressive expansion of Acacia senegal
and Acacia mellifera resulted changes in the original species composition of livestock in favor of
camels and goats, and significant reduction of cattle and sheep (grazers). Intensified intervention
from external agents (governmental and non–governmental organizations) to improve the
livelihoods pastoralists is needed before conditions become worse. Both local authorities and
external agents should focus on interventions and programs that facilitate crop cultivation in these
areas. However, supporting crop cultivation should be based on mutual consultation and land use
principles and should consider longer-term ecological and social costs. Assistance including
development of irrigation infrastructure, provision of farm tools, covering initial costs of farm
operations (such as costs of labor for tillage), provision of improved seeds and other related farm
inputs, logistic and advisory support are needed.
Woody plant measurements for the two sites differed markedly, and most of the measured woody
species attributes such as species composition, density of matured woody plants, and canopy
cover were higher in site I than in site II. Species composition in site I was dominated by A.
mellifera and A. senegal species. However, in site II the species composition was dominated by
A. tortilis, S. persica, A. nilotica, A. mellifera and A. senegal species. The density of matured
woody plants in site I was 2.4 times that of in site II. Density and canopy cover measurements
indicate site I, has crossed the critical threshold level for encroachment and had been encroached
by acacia species. However, the lower density of woody plants in site II indicates the site is not
encroached. Acacia mellifera and Acacia senegal were the most important, dominant and
encroaching woody plants in site I.
59
Encroachment of the rangeland by acacia species confirms the need to introduce effective and
feasible woody species reduction measures such as careful community based and participatory
interventions to improve the condition of the rangeland. The sustain pastoralism in the study area;
and to restore the productivity and stability the rangelands should be the first priority to be done.
Besides, the formulation of a policy to manage woodlands and savannas needs to be seen as an
urgent priority. Thus, the use of indigenous technical knowledge of the communities augmented
by scientific methods is crucial in the protection and rational use of woody and other plants in
general. Proper range management should be a prerequisite before other measures of
improvement. Employing rangeland monitoring and evaluation system helps in prediction or
early detection of an impending threshold and it will allow management action to be taken, to
maintain or achieve desirable botanical structure and productivity levels.
The proportion of young plant (saplings) of woody plants was different in both sites. The
proportion of A. mellifera and A. senegal species in both sites was higher than saplings of other
species. This indicates encroachment by A. mellifera and A. senegal species would continue as a
threat to the productivity and sustainability of the rangeland of the study area. A. mellifera and A.
senegal species possessed high number of saplings in site II. This high number of saplings may
indicate A. mellifera and A. senegal species were continued to expand and will dominate in site
II. High number of saplings in site I also indicate density of the woody plant will increase in the
future and shrub/ bush thickening will continue as a major problem unless an appropriate solution
is taken. The primary focus should be protecting the unencroached site not to be encroached with
shrubs/ bush. Control should start with key areas where young shrub populations have invaded
and should not be indiscriminate but selective. Further studies to understand the extent of
invasion and other associated parameters of soil and herbaceous plants need to be done. Research
60
should also be made on range ecology that focuses on physiological relations between targeted
encroacher species and on possible control methods by considering their environmental impact
and social acceptability.
Site II was more diverse and even than site I attaining a higher species diversity and evenness
index. Woody plants density and heavy grazing adversely affected diversity, relative abundance
and occurrence of other woody species. Consequently, the encroachment might result in
reduction of the carrying capacity of the site. The encroached rangeland may not easily be
restored by implementing a single controlling method. Projects that introduce a number of socio-
economic incentives that would encourage pastoralists to participate in bush clearing (thinning)
programs to restore encroached rangelands and to control further encroachment by destroying
seedlings and saplings of these acacia species should be designed. Even though there is no
enough herbaceous fuel loads to implement use of fire, approaches that integrate both traditional
and modern bush burning systems should be employed to gain the anticipated results. Part of
rangelands can be kept free of grazing and disturbance for few rainy seasons to use grass as a fuel
to burn the rangelands. On the other hand, reducing livestock number by providing market
facilities and improving productivity per head, decrease the contribution of overgrazing to
expansion of bush encroachment.
61
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APPENDIX
Appendix 1. Household Survey Questionnaire
General Information about Respondent
Date Enumerator/Recorder
Location/ Kebele Village
Name of Respondent Age Sex
Tribe Clan/group Rangeland site Name
1. Household information
1.1 What is your current job?
1. Pastoralist 2. Agro-Pastoralists 3. Daily Laborer 4. Government employee 5. Others
1.2 For how long did you live in this area (locality)? (Year) _________________
1.3 How many members do you have in your household /Family size/?
(1) Male ____________ (2) Female ____________ Total ____________
2. Resource Utilization, Vegetation Cover Changes & Perception on Encroachment
2.1 What is the condition of your rangeland looks like? (1) Good (2) Fair (3) Bad
2.2 Do you observe some changes from previous times? (1) Yes (2) No
2.3 What are the major changes you observe on the rangeland? (Rank)
3.4 What are the most important causes contributing to rangeland vegetation change? (Rank)
1) Drought 2) Overgrazing 4) Tree looping & clearing 5) Woody vegetation encroachment
6) Soil erosion 7) Poor rangeland management practice 8) I don‟t know 9) Other (specify)
2.4 What measure has been taken to rehabilitate rangeland degradation? (Rank)
2.5 What are the major feed resources available for your animals in your area?
1. Grasses and herbs 2. Browses 3. Agricultural by-products 4. Other (Specify)
2.6 How long does the annual grasses and herbs serve as a feed for livestock?
2.7 What is the common grazing system in your area?
1. Continuous grazing 2. Rotational grazing 3. Deferred grazing 4. Others (specify)
2.8 Do you conserve feed to your animals? 1) Yes 2) No
2.9 If No, Why?
2.10 If Yes, When and Why?
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2.11 What is the type of feed that you conserve for your animal?
1) Hay 2) Crop residue 3) Others (specify)
2.12 Is there a critical feed shortage in your area? 1) Yes 2) No
2.13 If yes, mention the months it often occurs?
2.14 What are the strategies used during these periods? (Rank in their priority)
(1) Sale of animals (Which age category) (2) Migration to other places (3) Looping of
browse trees (4) Use of conserved feeds & enclosures (5) Others (specify)
2.15 Do you think land cover change determine feed availability for livestock? (1) Yes (2) No
2.16 Do used to practice prescribed fire to management your grazing land? 1) Yes 2) No
2.17 Do you practice burning these days? 1) Yes 2) No
2.18 Do you believe that absence of fire on bush/ shrub contributed to the change of rangeland
vegetation composition in this area? 1) Yes 2) No
2.19 Do the absence of fire contributed to the spread of woody vegetations? 1) Yes 2) No
2.20 Are there any encroaching woody species in the rangelands? (1) Yes (2) No (If yes list &
rank)
2.21 Are there woody and herbaceous species which extinct or declining from time to time in
your community? (1) Yes (2) No
2.22 (If yes) list them & rank
2.23 Which activities do you think the most detrimental to the most important woody species?
1. Human activities 2. Livestock 3. Natural hazards 4. Encroachment 5. Others (specify)
2.24 Which do you think the most detrimental to the most important herbaceous species?
1. Human activities 2. Livestock 3. Drought 4. Encroachment 5. Others (specify)
2.25 Are there woody species that are introduced recently in your community?
3. Drought and mobility pattern
3.1 Do you encounter drought in this area during the past times? 1) Yes 2) No
3.2 How frequent did you encounter drought in this area (years)?
3.3 What are the consequences of drought in the previous years? (Rank)
1. Death of livestock 2. Migration 3. Death of human beings 4. Poor herbaceous cover
5. Woody plan encroachment 6. Others (specify)
3.4 Do you practice migration? (1) Yes (2) No
3.5 How is the frequency of migration in the past few years? (1) Increasing (2) Decreasing
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3.6 How long do you stay? Months
3.7 What is your attitude towards migration?
3.8 Mobility pattern and seasons
Pattern Location
Nomadic
Transhumance
Sedentary
3.9 Do you think woody vegetation encroachment contribute for the increment of migration?
3.10 What measure do you take to reduce mobility? (List & rank)
4. Socio-economic aspects
4.1 What is the income source of your household?
(1) Primary: A) Livestock rearing B) Cultivation C) Trade D) Others (specify)
(2) Secondary: A) Livestock rearing B) Cultivation C) Trade D) Others (specify)
4.2 Are there any socio-economic changes observed due to vegetation cover change (Rank)?
4.3 Do change in rangeland cover contributed for the occurrence of some human diseases?
1) Yes 2) No
4.4 If yes, mention of the diseases?
4.5 List problems encountered by encroaching woody plants on animals?
4.6 How is feed availability for livestock due to land cover change in the past few decades?
1) Increasing 2) Decreasing 3) No change occurred
4.7 Is there conflict that arises due to grazing land and water in the past few decades?
1) Yes 2) No
4.8 Between whom it commonly occurs and its frequency?
4.9 Did the herd composition changed due to the land cover change? 1) Yes 2) No
4.10 Which type of livestock is most affected by the change (Positively & Negatively)?
4.11 What is the effect land cover change on food insecurity and vulnerability to food-aid?
4.12 Is there any change on your family feed consumption behavior due to the land cover change
and how?
4.13 How is your family dependency on purchased cereals for consumption in the past few years?
1) Increased 2) Decreased 3) No major change
4.14 Because of woody plant encroachment is there any change on work load and how?
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4.15 Which type of gender is more affected related to land cover change and how?
4.16 What is the effect of land cover change on educational access on your family?
4.17 How do you compare your household income and expense balance for purchased food
items? 1) Negative 2) positive 3) Not changed
5. Production system
5.1 What is the current livestock population in number in your stock?
Cattle Camels Sheep
Goats Equines Others
5.2 What are the major livestock production constraints in the area?
No. Constraints Degree of influence (rank)
1 Feed shortage
2 Livestock disease
3 Re-current drought
4 Shortage of water
5 Market problem
6 Conflict
7 Replacement of natural grasses with bush
8 Others (specify)
5.3 What is the nature of land holding pattern? (1) Communal (2) Privately owned (3) Both
5.4 How do you use the land you have? (If not pastoralist)
1. Cultivation ha 2. Grazing reserve ha 3. Others (specify)
5.5 Have you been practicing agriculture before? (1) Yes (2) No
5.6 What is your opinion on cultivation practice?
For Agro-pastoralists
5.7 How long have you been practicing agriculture? years, and what was your
major occupation before?
5.8 What are the main reasons to start agriculture (if you were a pastoralist before)?
5.9 What are the main crops you grow? (Rank)
5.18 How do you get the consequences of cultivation? (1) Encouraging (2) Discouraging
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Appendix 2. Cross tabulation and chi-square test results for socio-economic survey
1. Perception on rangeland condition
Pearson Chi-Square = 25.364, DF = 2, P-Value = 0.000
Likelihood Ratio Chi-Square = 32.537, DF = 2, P-Value = 0.000
2. Perception on effect of Parthenium hysterophorus
Pearson Chi-Square = 12.754, DF = 1, P-Value = 0.000
Likelihood Ratio Chi-Square = 17.010, DF = 1, P-Value = 0.000
3. The contribution of absence of fire for encroachment
Pearson Chi-Square = 9.600, DF = 1, P-Value = 0.002
Likelihood Ratio Chi-Square = 10.126, DF = 1, P-Value = 0.001
4. Effect of vegetation cover change on feed availability
Pearson Chi-Square = 7.813, DF = 1, P-Value = 0.005
Likelihood Ratio Chi-Square = 8.122, DF = 1, P-Value = 0.004
5. Mobility pattern of pastoralists
Pearson Chi-Square = 9.108, DF = 2, P-Value = 0.011
Likelihood Ratio Chi-Square = 12.204, DF = 2, P-Value = 0.002
6. Perception on frequency of migration
Pearson Chi-Square = 19.200, DF = 2, P-Value = 0.000
Likelihood Ratio Chi-Square = 24.345, DF = 2, P-Value = 0.000
7. Perception on contribution of encroachment for migration
Pearson Chi-Square = 30.000, DF = 1, P-Value = 0.000
Likelihood Ratio Chi-Square = 32.806, DF = 1, P-Value = 0.000
8. Income diversifying activities
Pearson Chi-Square = 2.257, DF = 1, P-Value = 0.133
Likelihood Ratio Chi-Square = 2.279, DF = 1, P-Value = 0.131
9. Perception on effect of encroachment on household income
Pearson Chi-Square = 20.333, DF = 2, P-Value = 0.000
Likelihood Ratio Chi-Square = 26.585, DF = 2, P-Value = 0.000
10. Perception on effect of encroachment on herd composition of households
Pearson Chi-Square = 825.319, DF = 4, P-Value = 0.000
Likelihood Ratio Chi-Square = 905.181, DF = 4, P-Value = 0.000
11. Perception on contribution of encroachment for food insecurity and dependency on food-aid
Pearson Chi-Square = 11.818, DF = 2, P-Value = 0.003
Likelihood Ratio Chi-Square = 12.205, DF = 2, P-Value = 0.002
12. Attitude towards agro-pastoralism
Pearson Chi-Square = 0.203, DF = 1, P-Value = 0.653
Likelihood Ratio Chi-Square = 0.203, DF = 1, P-Value = 0.652
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Appendix 3. Woody Species Attributes
Appendix 3.1 Botanical composition (BC), Canopy cover (CC), Density (D) and Basal area (BA) of
woody plant species in site I and II.
Species BC (%) CC (%) D (N/ha) BA (m
2/ha)
Site I Site II Site I Site II Site I Site II Site I Site II
A. mellifera 50.96 12.36 23.14 1.86 12091 1100 39.9079 3.82
S. persica 1.56 10.67 0.00 0.76 371 950 3.4561 7.675
A. senegal 37.34 7.02 31.61 7.97 8860 625 37.4396 4.7475
C. rotundifolia 1.58 6.18 0.00 0.93 375 550 1.5975 2.29
A. nilotica 0.94 10.67 0.55 5.14 224 950 2.17 7.96
F. sycomorus 0.32 6.74 0.16 0.44 75 600 0.285 2.1575
G. villosa 0.21 2.53 1.54 2.26 50 225 0.1225 1.0675
D. glabra * 3.09 * 0.00 * 275 * 1.0575
B. aegyptiaca 0.21 5.06 0.31 3.22 49 450 0.5625 1.9425
A. tortilis 0.83 11.24 1.92 7.07 197 1000 2.135 10.26
D. angustifolia 0.32 2.53 0.52 0.47 75 225 0.2975 0.77
Z. mauritiana 0.11 1.69 0.32 1.24 25 150 0.0725 0.6275
A. etbaica * 2.81 * 0.00 * 250 * 2.0675
A. nubica 1.44 3.37 0.14 8.00 342 300 2.7461 3.1575
C. purpurea * 1.12 0.41 100 0.6175
A. horridae 0.32 3.65 0.00 1.15 75 325 0.31 4.8775
C. procera * 1.12 * 0.00 * 100 * 0.42
N. glauca * 2.53 * 0.09 * 225 * 0.4675
B. coriaceae 1.37 1.69 2.46 0.92 325 150 1.0825 0.375
G. ferruginea 2.49 3.93 5.39 0.15 591 350 1.835 1.6675
TOTAL 100 12.36 68.06 42.08 23725 8900 94.0197 58.025
* Values not recorded in the site for the mentioned species
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Appendix 4. Woody Species Data
Appendix 4.1 Woody species total mean density (N/ha )for site I and site II along transects
Sites Transects
TR 1 TR 2 TR 3 TR 4 TR 5 TR 6 TR 7 TR 8 TR 9
Site I 2475 2950 2375 2700 2550 2550 2950 2575 2600
Site II 1150 1075 1225 1250 1050 1000 1125 1025 -
Appendix 4.2 Woody species total mean canopy cover (%) for site I and site II along transects
Sites Transects
TR 1 TR 2 TR 3 TR 4 TR 5 TR 6 TR 7
Site I 66.53 89.71 74.85 92.75 84.85 4.95 62.8
Site II 46. 17 58.99 36.02 45.04 50.44 43.08 14.85
Appendix 4. 3 Woody species SAPLINGS mean Density (N/ha) for site I and site II along transects
Sites Transects
TR 1 TR 2 TR 3 TR 4 TR 5 TR 6 TR 7 TR 8 TR 9
Site I 875 1025 450 1025 475 675 1025 350 800
Site II 500 300 375 250 475 675 725 250 -
Appendix 5. Species Diversity along Transects
Sites Transects
Over all site
Index TR 1 TR 2 TR 3 TR 4 TR 5 TR 6 TR 7 TR 8 TR 9
Site I 1.37 0.58 1.29 0.95 1.23 1.21 0.63 0.8 1.12 1.225
Site II 1.31 2.21 2.14 2.1 2.03 2.03 2.04 1.77 - 2.704
Appendix 6. Evenness of Species along Transects
Sites Transects Over all site
Index TR 1 TR 2 TR 3 TR 4 TR 5 TR 6 TR 7 TR 8 TR 9
Site I 0.71 0.84 0.66 0.69 0.76 0.75 0.91 0.58 0.81 0.45
Site II 0.81 0.92 0.98 0.95 0.98 0.92 0.93 0.91 - 0.92
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Appendix 7. Cross tabulation and chi-square test of species attributes between the two sites
1. Cross tabulation and chi-square test results for species composition of woody plants
Species DF Pearson Chi-Square P-Value
Likelihood Ratio
Chi-Square P-Value
A. mellifera 8 73.826 0.000 88.535 0.000
A. senegal 8 131.221 0.000 116.149 0.000
S. persica 8 53.751 0.000 49.070 0.000
G. ferruginea 3 26.088 0.000 35.431 0.000
A. tortilis 7 73.558 0.000 43.589 0.000
A. nubica 4 40.000 0.000 51.796 0.000
A. nilotica 6 81.160 0.000 52.294 0.000
B. coriaceae 2 25.000 0.000 34.617 0.000
C. rotundifolia 3 22.750 0.000 28.638 0.000
B. aegyptiaca 5 41.000 0.000 15.983 0.000
A. horridae 2 9.931 0.008 9.327 0.008
D. angustifolia 1 1.326 > 0.05 2.126 >0.05
F. sycomorus 4 56.000 0.000 23.397 0.000
G. villosa 3 23.000 0.000 13.590 0.000
Z. mauritiana 1 15.000 0.000 7.348 0.000
2. Cross tabulation and chi-square test results for relative dominance of woody plants
Species DF Pearson Chi-Square P-Value Likelihood Ratio
Chi-Square P-Value
A. mellifera 8 68.316 0.000 74.411 0.000
A. senegal 8 150.762 0.000 144.771 0.000
S. persica 8 84.862 0.000 91.137 0.000
G. ferruginea 3 9.145 < 0.05 9.537 < 0.05
A. tortilis 7 135.859 0.000 100.042 0.000
A. nubica 4 62.000 0.000 83.613 0.000
A. nilotica 6 88.286 0.000 84.477 0.000
B. coriaceae 2 16.000 0.000 21.170 0.000
C. rotundifolia 3 23.906 0.000 30.692 0.000
B. aegyptiaca 5 32.000 0.000 30.885 0.000
A. horridae 2 12.692 0.000 10.395 0.000
D. angustifolia 1 1.587 > 0.05 2.307 > 0.05
F. sycomorus 4 37.000 0.000 20.824 0.000
G. villosa 3 14.000 0.000 7.205 0.000
Z. mauritiana 1 16.000 0.002 7.481 0.002
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3. Cross tabulation and chi-square test results for importance value index of woody plants
Species DF Pearson Chi-Square P-Value Likelihood Ratio
Chi-Square P-Value
A. mellifera 8 189.193 0.000 228.977 0.000
A. senegal 8 360.494 0.000 338.988 0.000
S. persica 8 217.538 0.000 241.642 0.000
G. ferruginea 3 68.720 0.000 92.211 0.000
A. tortilis 7 298.164 0.000 246.146 0.000
A. nubica 4 157.000 0.000 212.982 0.000
A. nilotica 6 260.251 0.000 242.316 0.000
B. coriaceae 2 81.000 0.000 101.673 0.000
C. rotundifolia 3 75.499 0.000 97.040 0.000
B. aegyptiaca 5 119.000 0.000 93.954 0.000
A. horridae 2 51.551 0.000 51.324 0.000
D. angustifolia 1 8.599 0.003 12.895 0.003
F. sycomorus 4 147.000 0.000 105.299 0.000
G. villosa 3 70.000 0.000 67.193 0.000
Z. mauritiana 1 47.000 0.000 53.402 0.000
