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Rainforest Information Centre Educational
Supplement
RAINFORESTS OF THE WORLD
What Are Rainforests?
There are many definitions. In ecological terms, rainforests have been defined as "multi-storied closed, broad leaved forest vegetation with a continuous tree canopy of variable height and with characteristic diversity of species and life forms" . Tropical rainforests in particular possess an astonishing array of flora and fauna. In fact, at least half of the Earth's species are found in rainforests.
Contents
1. The Importance of Rainforests
1.1 Biodiversity
1.2 Medicines
1.3 Food Diversity
1.4 Climate
1.4.1 Water and Temperature
1.4.2 The Greenhouse Effect
1.5 Watersheds
1.6 Homeland for Forest Peoples
1.7 Non-material Values
1.8 Decay and Renewal in the Rainforest
2. Rainforest Facts
3. Deforestation in the Temperate North
1. The Importance of Rainforests
Rainforests have been called the womb of life because
they are home to 50-90% of the species on Earth. Worldwide, several hundred million
forest-dwelling people live in or depend on rainforests. Many of the world’s
important food crops and domestic animals have been developed from rainforest species.
Human beings depend on rainforests in numerous ways, but it would be wrong to suggest that
they should be preserved purely so that they can be exploited by humans.
1.1 Biodiversity
Because of tropical deforestation, it has been estimated that at least 40 species are perishing every day. This is a rate hundreds of times faster than at any period in recent geological time.
Tropical
forests cover only 12 per cent of the land area of the Earth, yet they are home to between
50 and 90 per cent of the world's species. They contain 90% of non-human primates, 40% of
all birds of prey and 80% of the world's insects and over 60% of all known plants. Because
one species in a tropical forest may be found in a small area and nowhere else, the
destruction of relatively small areas of forest can cause extinctions.
No one knows just how the rest of the global ecosystem depends on rainforests, but we may find out in the next 30 to 50 years. That is how long it is estimated that it will take for tropical forests to disappear altogether if current trends continue.
This situation has been likened by biologists Anne and Paul Ehrlich to an aeroplane losing the rivets which keep it together. No one knows how many rivets the plane can lose before it falls apart.
1.2 Medicines
Rainforests are a vital source of medicines. Today, less than 1% of the world's tropical forest plants have been tested for pharmaceutical properties, yet at least 25% of all modern drugs came originally from rainforests. Most were first discovered and used by indigenous peoples.
Annual worldwide sales of plant-derived pharmaceuticals currently total $20 billion. These include such drugs as Digitoxin, Vincristine, Emetine, Physostigmine, Atropine, Morphine, Reserpine, D-Tubocurarine, and Quinine. All were first used by rainforest shamans and healers.
An impressive 70% of all plants known to have anti-tumour properties come from tropical rainforests. Any one of these could lead to breakthroughs in the treatment of cancer. The potential of this living pharmaceutical factory remains almost completely untapped.
The potential and fragility of the rainforests as an invaluable source of medicine is clearly illustrated in the following account from the World Rainforest Report no.26:
"Starting with twigs from a Malaysian gum tree, researchers in 1991 isolated a compound that blocked the spread of the AIDS virus in human cells. The team sent biologists racing back to Malaysia for more samples from the tree. But when they got to the swamp, the tree was gone, it had been cut down. And no tree found since has produced the same compound. " No identical trees have been found in the immediate area and samples from the same species found elsewhere did not yield the same compound.
In Sarawak, the Penan people use over 50 medicinal plants which they harvest from the primary forest - plants that are used as poison antidotes, contraceptives, clot ting agents, general tonics, stimulants, disinfectants, remedies for headaches, fever, cuts and bruises, boils, snake bite, toothache, diarrhea, skin infections and rashes, and for setting bones.
1.3 Food Diversity
Apart from being an invaluable source of medicines, rainforests offer a veritable bounty of foods. Of an estimated 75,000 edible plants found in nature, only 150 enter world commerce and only 20, (mostly domesticated cereals), stand between human society and starvation. This means that modern agriculture is vulnerable to pests, disease and changes in climate.
Genes from wild plants are used to fortify modern varieties, and are likely to become increasingly important for this purpose. In the 1920's, when disease decimated the sugar cane crop in South America, genes from a wild species in Java saved the industry from ruin. In 1970, wild coffee from Ethiopia's vanishing forests saved Latin America's plantations from devastation. Every modern rice plant contains a gene resistant to grassy stunt virus, a major rice disease. The gene was discovered 25 years ago in just two seeds from Indian forests. No other seeds containing the resistant gene were ever found again.
Tomato varieties have been improved by crossbreeding with wild tomatoes from Ecuador, Chile and Peru. Similar crossbreeding has improved other varieties of fruits and vegetables.
In the tropics, there are wild trees that yield 650 pounds of oil-rich seeds a year, a fruit with more vitamin C than oranges, a palm with more vitamin A than spinach and another palm whose seeds contain 27% protein. There is a palm whose seed oil is indistinguishable from olive oil and a tree producing resin which can be used unprocessed to run a diesel engine.
There are shrubs with fruit containing compounds 300 times sweeter than sucrose, some with leaves coated in industrial grade waxes, seeds used for dyes and plants producing insecticides. There are also plants that yield twine for weaving baskets, furniture and often even beautiful and elaborate cladding for the homes of forest dwelling people.
Crops originating in the rainforests include rice, quinine, rubber, coffee, bananas, eggplants, lemons, oranges, tea, cacao, cashews, cassava, tapioca, peanuts, pineapples, guavas, brazil nuts, paw paws, avocadoes and many more.
1.4 Climate
1.4.1 Water and Temperature
Rainforests have been described as the global heat and water pumps because of their influence on climate. Rainforests are dark, and like a dark car parked in the hot sun they absorb heat. Above a rainforest the air is cooler so it is more likely to rain. Inside the rainforest, beneath the dense canopy, humidity stays high and steady compared with the outside world. The forests stay wet and evaporate vast quantities of water through their foliage and into the air above, forming clouds. Some falls again as rain in the tropics but often clouds are carried great distances to fall as rain in the mid latitudes, often as far away as Europe and Australia.
The hotter air that exists over deserts and grasslands that replace the rainforests after logging or clearing, discourages the clouds and the deserts remain dry. As rainforests disappear this will dramatically affect the water circulation of the atmosphere and is likely to alter weather patterns thousands of miles away.
1.4.2 The Greenhouse Effect
As a stable system, all forests hold vast amounts of carbon in their biomass. When forests are destroyed, vast amounts of carbon are released into the atmosphere as C02. Because CO2 is the major greenhouse gas, this adds to global warming. Up until now the increase of C02 in the atmosphere has been largely due to the burning of fossil fuels such gas, oil and coal, but this could change as more forests are destroyed. In one year, fires from the Amazon alone produced 500 million tons of C02, estimated to be 10% of the world's total annual atmospheric emissions. Contributing to these C02 emissions is the burning and decomposition of pulp and paper made from these forests.
Atmospheric C02 traps the sun's heat in much the same way as the glass of a greenhouse, and by warming the atmosphere, it also, has the potential to dramatically change global weather patterns.
1.5 Watersheds
One of the most vital functions fulfilled by forests is the control of rainfall run-off to waterways.
Imagine rainforests as huge sponges or watersheds soaking up the rain and storing it, releasing a little at a time. In a well forested watershed, 95% of annual rainfall is trapped and then released slowly but surely over time, replenishing ground water and keeping streams and rivers flowing through the dry seasons. This constant supply of clean water running into streams, rivers, lakes, reefs and lagoons is vital for replenishing the homes of their myriad creatures.
When the forest is removed, there is no longer any sponge to absorb the water and the result is massive flooding, soil erosion and siltation of the waterways. Siltation causes the water to become choked with mud and all life that depends on that clean water eventually suffocates.
1.6 Homeland for Forest Peoples
Worldwide there are 300million indigenous people, and approximately 50 million of them live in tropical forests. They rely almost exclusively on the forests for their survival needs.
Rubber tappers are not indigenous to the forests of the Amazon but have learnt to live sustainably in the forest. Like the indigenous tribes who depend on the forests, they are under threat from the destruction of their forest homes.
1.7 Non-material Values
The wonder and spiritual importance of the rainforests to all that live in and around is profound. They are important even for those of us who may just enjoy a stroll through them on weekends and holidays. It is impossible to try to put a value on rainforests for all the riches they can and do offer.
1.8 Decay and Renewal in the Rainforest
In a "forest system" nothing is wasted. Plants are constantly shedding leaves and bark which then mix with the excreta of living forest animals and the carcasses of dead ones to form a rich layer of humus on the forest floor. Micro-organisms, insects and fungi break down this humus and convert it into nutrients for the soil. Through the soil, with the help of water, these nutrients are taken up, absorbed through the roots of the trees and plants, nourishing them, which in turn, provides food and shelter for birds and animals. So the process of decay, recycling and renewal goes on.
All things have value in a natural forest no matter what their age or condition. The youngest groundcover provides a quick snack for a passing wallaby, while an old dead tree offers many nooks and crannies in which anything from birds and possums to fungi and termites can make a home. Although rainforests may appear chaotic, in fact everything has its niche.
The soils of many rainforests are relatively infertile, despite the wealth of species they support. In fact, rainforests on Fraser Island off the coast of southern Queensland, Australia, grow in pure sand. When tropical rainforests are cleared for agriculture or grazing, they often are productive for only one or two seasons and then have to be abandoned. The lack of nutrients in these soils shows that in rainforests, nutrients are recycled very efficiently before they become part of the soil.
Traditional slash and burn farmers have adapted to tropical forest soils with efficient systems of rotation and fallow. No other form of agriculture has proved to be sustainable in tropical forest areas.
2. Rainforest Facts
Rainforests cover about 12% of the total land surface of the globe. They contain between 50 and 90 per cent of all species (World Rainforest Movement, 1990).
Tropical Forests are the Earth's oldest ecosystems. Fossil records show that the forests of South-East Asia have survived in their present form for at least 70 million years (Myers, 1992).
Rainforests have been called the "Lungs of the Earth", but the term is misleading. Although rainforests do release vast amounts of oxygen into the atmosphere, they absorb just as much through the decay of organic matter. However, they do play an important role in regulating the Earth's atmosphere by storing carbon in their biomass. When forests are destroyed, the carbon they contain is released into the atmosphere in the form of carbon dioxide.
In 1989, the Government of Colombia recognised the claim of tribal people to half of the Colombian Amazon. The government acknowledged that the Indians are the best guardians of the rainforest (New Scientist Dec 1989).
One river in Brazil was found to contain more species of fish than all the rivers in the USA (World Rainforest Movement, 1990).
The largest forest fire in recorded history occurred in Kalimantan, the Indonesian section of the island of Borneo in 1982-3. The fire began after a prolonged drought in the fields of farmers who moved into the area after it had been opened up by logging (Collins, Sayer and Whitmore, 1992).
Between 1981 and 1990, seventeen million hectares were destroyed each year. The same period saw the rate of tropical forest loss double. If this rate of increase in defore- station were to continue, all remaining tropical forests would be destroyed in less than thirty years. (Rainforest Information Centre, 1991).
Further facts in figures:
Rates of Destruction:
17 million hectares a year
-- an area larger than Switzerland
About 1 hectare a second
-- about a football field a second
Species Extinction
about 50 species per day
Tropical timber Exports:
Number of exporting countries, 1991: 33
Number still exporting in the year 2000: 10
(World Bank estimate)
Indigenous Tribes:
Number of native rainforest societies
destroyed in Brazil in 1st half of 20th century: 87
Number of rainforest cultures still in
existence worldwide: 1,000 (approx)
Number threatened by development
plans: 1,000 (approx.)
Worldwide tropical forest
1980: 18.8 million ha.
1990: 17.1 million ha.
2000: 1.54 million ha. (est.)
Expiry Date for all
Rainforests
estimates range from 30 to 50 years
if present trends continue
Asia's tropical forest:
1980: 310.8 million ha.
1990: 274.9 million ha.
2000: 239 million ha. (est.)
The Americas tropical forest:
1980: 923 million ha.
1990: 839 million ha.
2000:756 million ha. (est.)
Africa's tropical forest
1980: 650.3 million ha.
1990: 600.1 million ha.
2000: 549 million ha. (est.)
3. Deforestation in the Temperate North
The loss of the world's tropical forests is one of the greatest calamities ever to face humankind. However this should not divert attention from the destruction of temperate forests. In Europe, forest cover as a proportion of the total land area now stands at 30% or less in most countries. In North America, about 12% of the original forest area remains (World Rainforest Movement, 1990).
Since the opening of Russia to investment from the West, the Siberian boreal forests, the largest forested area in the world, have become under increasing threat (Wood Rainforest Report no.24).
Throughout the temperate regions pollution and pollution-related diseases are damaging large proportion of trees. A 1988 study found that in Germany, 52% of all trees were damaged. In Britain, the figure is 64% and in Czechoslovakia, 70%.
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