Where is Amazon ?Where is Amazon ?

Where is Amazon ? one of the world's great rainforests Amazon river runs 3,000 miles from the A

ndes to the sea The vast Amazon basin covers more than t

wo and a half million square miles

Climate

High and constant temperature—27*c Small annual and diurnal temperature

range Very little seasonal difference Heavy annual rainfall—2ooomm Reliable and evenly distributed High humidity—over 80%

Deforestation

砍伐森林

CharacteristicsCharacteristics It involves the permanent destruction

of indigenous 天生的 forests and woodland for farming or commercialpurpose.

For subsistence purpose, trees are cut down by primitive tools & burnt. The remaining ash is used as fertilizer for farming.

For commercial purpose Trees are cleared extensively with the he

lp of modern technology ( e.g. Electric saw, road ) to make furniture and paper.

Trees are removed for rearing , mining .This will give greater impact on the environment because there is no plant to protect the soil . The land was abandoned after used.

Data about Data about deforestationdeforestation

In AmazonIn Amazon

Deforestation of Brazil

Dead forestDead forest

DeforestationDeforestation

Original forestOriginal forest

Deforestation in AmazonDeforestation in Amazon

Shifting Cultivation

刀耕火種

Characteristics It is a type of subsistence [ 維持生活 ] farming due

to crops are grown for household use only It is practiced by native tribes [ 部族 ] in hilly areas Climate is equatorial climate with high temperatur

e and abundant rainfall Population density is low Farms are scatterly distributed , separated by fore

sts or savanna Fields are small

Clearing of trees provides farmland The method of “ slash and burn “ [ 猛砍 + 燒毀 ] is a

dopted to clear and fertilize the farmland Some simple and primitive [ 原始的 ] tools , like woo

den plough , are used to cultivate the farmlands and labour input is low

The crop yield is low Farmland is temporary [ 臨時的 ] as soil becomes inf

ertile after heavy leaching , and two to three years of cultivation

“ Bush fallowing “ will be practiced as the soil becomes infertile

The application of chemical fertilizers and the construction of irrigation network are unnecessary

Shifting cultivators abandon [ 放棄 ] the old farmland and move to a new site to start cultivation again

As harvest [ 收穫物 ] is low and unreliable , shifting cultivators also practice hunting [ 打獵 ] , fishing , fruit-gathering [ 水果採集 ] and livestock rearing to increase food supply

Shifting cultivationShifting cultivation

Map

Rainfall in Amazon

Data about shifting cultivation

With the help of stone axes [ 斧 ] and machetes , the Amerindians clear a small area of about 1 hectare [ 公頃 ] in the forest .

Sometimes the largest trees are left standing to protect young crops from the sun’s heat and the heavy rain ;There are also trees which provide food , such as the banana and kola nut [ 可樂果 ]left behind or planted purposefully to protect crops. The buttress roots of the giant [ 巨大的 ] trees are left also.

The main crop , manioc [ 木薯 ] , is planted along with yams ( which need a richer soil ) , pumpkins , beans , tobacco [ 煙草 ] and coca [ 古柯 ] .

The Amerindian diet is supplemented by hunting , mainly for tapirs and moneys , fishing and collecting fruit .

Impact of

deforestation and shifting

cultivation in Amazon

Why changed? Where the population density is low enough to permit sufficiently l

ong period of fallow, the soil fertility may be maintained by means of grassland (in the savanna regions), and by secondary growth of forest (in forest areas), then this method of farming may be considered suitable to primitive tribes with a low level of technology

Recent government policy of encouraging the in-migration of landless farmers from other parts of the country , together with the development of extensive commercial cattle ranching , has meant that sedentary [ 固定 ] farming is rapidly replacing shifting cultivation . After just a few years, as should have been foreseen, large tracts of some cattle ranches and many individual farms have already been abandoned as their soils have become infertile and eroded

Atmosphere The local energy budget is changes

reduces the surface vegetation cover and raises the surface radiation from about 13% - 20%more solar radiation is reflected , the less the surface will be warmed

however, this cooling effect is rejected by a great reduction of evapo-transpiration that transformed into heat and making the surface hotter

Atmosphere-global impact Burning, urban development (e.g. industry

and mining) may increase the production of carbon dioxide.

Carbon dioxide cannot go out to the space as there is less vegetation to absorb carbon dioxide.

This leads to increase the air temperature and the planet becomes warmer and warmer. (Greenhouse effects)

Global warming may lead to the melting of polar ice and rising the sea level

Lithosphere

Biochemical cycle will break up It is because the less the vegetation, the less t

he litter. The fungi still decompose very fast while there are only a little amount of litter.

An insignificant part of soil is actually washed away by rain, the quick recycling mechanism is broken

Lithosphere - local effect Large areas are wasted. This leaves the land exposed to heavy rain and leaching resulted. The productivity of the rainforest depends upon the rapid and

unbroken recycling of nutrient. Once the forest has been cleared, the nutrient cycle is broken.

Widespread soil exhaustion makes it difficult and slow to recover the land.

Soil erosion often results after the removal of vegetation cover. Heavy, afternoon, convectional rainstorms hit the unprotected

earth. The humus in the upper layers of the soil is rapidly destroyed or washed down (causing erosion and leaching)

Lithosphere-local effect With the source of humus removed (litter), and in the absence

[ 缺乏 ] of fertilizer and animal manure [ 糞肥 ] , the ferralitic soil rapidly lose their fertility and the soil is rapidly leached by the frequent and heavy tropical rain.

Raindrop 雨滴 impact and rain washes erode the soil and carry it into streams, lakes and reservoirs that cause silting and flooding in the lowlands.

Within 4 or 5 years , the decline in crop yields and the re-infestation [ 繁殖 ] of the area by weeds force the tribe [ 部族 ] to shift to another part of the forest . Although shifting cultivation appears to be a wasteful use of land , it has no long-term adverse [ 有害的 ] effect upon the environment as , in most places , humus can built up sufficiently to allow the land to be re-used within 25 years if necessary

Hydrosphere It also changes local water cycle

Before deforestation, there are evapo-transpiration and so that there are only 30% runoff.

After deforestation, there are 90% runoff because no evapo-transpiration ...> leading to flood easily

It increases the rate of the process of laterization, which causes poor drainage. Moreover, it reduces infiltration and hence soil moisture content also reduces.

Hydrosphere -Influences on the area adjacent to the forest

Increases overland flow in the water records of River Maranon [ a tributary of the Amazon ] so that cause flood haz

ards

Biosphere People who live there will extinct because of

losing their home in rainforest. They will die easily as they are not suitable for the outside environment.

An increase in population often makes it necessary to shorten the period of fallow . This means insufficient time for the soil to recover and for the forest to regenerate

Biosphere Those wildlife habitats and species which may be

useful for human beings are threaten and extinct. The insects become extinct 滅絕的 before they have

been discovered. For example, the Brazil nut flowers will not produce

the nuts without large carpenter bees to visit their flowers.

The rainforest is also a home to numerous 眾多的 migratory birds 候鳥 .

Biosphere Of the estimated 6 million Amerindians living in

the Amazon rainforest when the European colonists arrived , only about 4 per cent remain today as a result of illnesses caught from and death inflicted by the invaders

Burning destroyed weeds and controls the growth of weed seeds for some time

Biosphere Adverse change in composition and structure of vegetation for example, the height, species, and density decrease. The structure of vegetation becomes from complicated to simple

Climatic climax community may be totally destroyed and turned into bare earth. The loss of vegetation leads to loss of animal life or extinction of some animal species.

The End

By By Lois Li Man Wai Lois Li Man Wai

Chan Yuen HungChan Yuen Hung Lo Wing SuetLo Wing Suet