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