Man environment relationships in TRF
F.6 geography
The impact of the environment on man
The Amazon Basin
Slash and burn or shifting cultivation is most common
The soil will rapidly depleted after one to two crops, the cultivators are forced to leave the clearing site and move to a new one
The process
Selecting the site
Clearing the forest
Burning off the dead vegetation
Planting crops
Weeding and harvesting the crop
migration
Selecting the site
Clearing is easy in primary forest cause little undergrowth
The secondary forest also dries out more easily
A steep hillside is usually choose because there is updraught to spread the fire
Clearing the forest
Take place at dry seasons
It is done by simple hand tools
Such method may protect the virgin forest
The tallest trees cut down first , it will drag down shorter tree on the path
Burning off the dead vegetation
The ashes will enrich the soil
Heavy clay soil dried out ,developing large cracks in which ash accumulates
People use only small digging sticks and hands hoe ( 鋤頭) for ploughing
The debris after burning off helps to reduce runoff and reduce erosion
Planting crops
Multi-storey agriculture are easily found
Yams are the ground crops
Millet are lower storey
Manioc beans or maize the third storey
Bananas, breadfruit ,other tree crops ,the upper storey
Advantages of mixed cropping
Reduce the amount of space to cleared
Lengthen the seasons of growth
Enables maximum return for the minimum effort
Provides more complete cover,shading the ground and prevent the growth of weeds
Different crops allow the best use to be made of soil, sunshine and rainfall
Provides insurance against the failure of any one type of crops
Ensure a more constant supply
Seeds are sown by mouth (spitting) or by using a primitive seed drill ( 種子鑽
子 ) (a hollow stick which enables seed to be dropped into the holes without having bend over )
The main crops are maize, pulses, green vegetables, yams and manioc (cassava)
Crop rotation helps to prevent soil exhaustion and erosion
Weeding and harvesting The swidden receives little attention during the growing period
Root crops can be left in the ground and dug up as required – one root crop providing enough food for a family for several days
Vegetables are hand-picked. When ready, cereals are dried, threshed ( 打穀)and husked (去穀類外皮 )
Migration
Tropical soil depleted easily (1 to 3 yrs)
Weed and undergrowth will invade easily at that time when the nutrient loss
Farming will leave the clearing and look for a fresh site
This allows the forest to reclaim the clearing and rebuild soil fertility. This is called bush fallowing
Natural hazard also cause migration : disease like malaria and sleeping sickness, disasters such as insect plagues and droughts and animal invasion
The land can be reused after a 8-20 year of bush fallowing when soil fertility has been restored
The village and way of life
Location : usually near the stream ,for food, transport, domestic use
Plan : 20 to 300 people ,in a single street or circular group
Typically village house : village house (long house)are elevated because avoid wet climate, termites, tigers and panthers ( 黑豹) cannot invade the house
Way of life
Use primitive tools
Fishing , hunting ,farming , weeding , harvesting, gathering
Plantation : cacao, cotton and rubber
Difficulties in timber production The wet and hot climate prevent people development of the TRFSpecies are mixed, no pure stand ,making cutting difficult Hardwoods have thick trunks and buttress root and are difficult to fellTransport difficultSwampy ground Insects ,disease Lianas ,climbers make movement in forest diffcult
The impact of man on environment The ecological impact of shifting cultivation :
- the direct burning of the organic matter can speed up the oxidation of the organic matter and humus in the top soil
- the primitive method can reduce structural damage to the soil. No chemical are used and thus no environmental hazards result
In some area, weeding is done manually and selectively to preserve trees seeding and spalings , adding forest regeneration
No draught animals are used ,so the return in relation to input is very efficient
Shifting Cultivation add variety to their food by hunting, fishing,gathering
The full vegetative cover can reduced erosion ,while multiple cropping reduce pest and disease hazard
Abandoning the clearingsAbandoning can cause soil erosion , structural damage and fertility decline together with weed invasion and disease
Long fallow period is need if want to resume fertility
Managed rotation of fields is better using the corridor system ( 走廊式輪植法 )
If shifting cultivation is subsistence purpose ,it pose lesser harm to the environment
Deforestation It generate many problems :Displacement of the rainforest Changes in the hydrology of the Amazon Basin accelerate surface runoff ,reducing infiltration , modify the fluvial regime Variation in run-off ,sediment load . Sedimentation are prevailed It will affect aquatic plans and animal
Deforestation may produce climate changes such as change in soil temperature, humidity, wind speed and insolation
Biomass reduction – it leads to soil erosion ,nutrient loss
Cattle ranching The removal of TRF for cattle ranching free nutrients from the biomass producing a reduction in nutrients
The pasture deterioration can lower the carrying capacity of land from 200 cattle /km² to 50-80 cattle /km²
Overgrazing, trampling and soil compaction also lead to accelerated erosion or poor drainage
Effects on aquatic resources
Reduce the supply of organic debris which is an important food supply for fish
It can alter run-off and erosion ,affecting the productivity of the streams by altering the water quality
Increasing population Increase pressure upon food producing land and reduce the period of essential bush fallow
Old clearing are reused sometimes, forest replaced by woodland or open grassland
Introduction of European agricultural
technique Geometrically arranged fields have reduced the protective ground cover, accelerating soil depletion through leaching
The introduction of deep ploughing and steel ploughs also increased erosion because they allow plots to be completely cleared ,exposing soil for erosion
Cash cropping brought changes in the life of the tribes (it brings personal gain and the possession of the land )
Other effect :
- Mining leaves behind mining pits full of water , it favour the development of malaria
Land development solution
An economically productive and ecologically stable system is need
One of the method is compartmentalizing ( 分隔 ) the landscape ,then apply separate management strategies to each unit
Use of the varzea Varzea is a place which have higher potential land
Intensive agricultural and use of aquatic resources can be practised here
But it should be controlled with a fixed fishing season and limited on the fish caught
The terra firma To protect the terra firma(upland savanna and forest ), there would be low intensity,shifting cultivation and plantations of selected tree and shrub crops
Large scale forest clearance for farming and ranching in these area would be stopped
Agricultural alternatives Agricultural/ silviculture ( 農耕做林學)is a possible alternative
The inter-planting of annual food crop, perennial food crops and slow-growing timber species
This system is a compromise between crop production and land protection
Population control
This can be used to prevent too much pressure on the land
Educational programmes to encourage some form of family planning are necessary
Native participation Cash cropping can allow specialization and capital formation in these underdeveloped areas
The tribes can use these profit to buy fertilizers ,tools and transport. Thus, improving the living standard