Peace and Environment News
* December 1994-January 1995

Rainforests: Their Nature and Importance

Where are the tropical forests?

Running like a girdle around the equator, tropical forests cover some 900 million hectares. They are divided between South America (58 percent), Africa (19 percent), Asia (10 percent) and Oceania (10 percent). Brazil contains almost 33 percent of the total, and Zaire and Indonesia each have 10 percent. Papua New Guinea, Bolivia, Colombia, Venezuela, Peru, Gabon and Burma each have over 200,000 square kilometres of tropical forest. Thus Brazil, Zaire and Indonesia jointly own more than half the world's tropical forests. Those of the Ivory Coast and of Nigeria are now virtually gone, cut down over the past forty years. Undisturbed by humans, rainforests are very stable ecosystems and contain ancient and diverse forms of life. In the Amazon jungle, for instance, over 2500 species of trees are known, with up to 400 in a single hectare.

Why are they so important?

Tropical forests are habitat for at least fifty percent of all the plant and animal species on Earth. As many as five million species provide a gene pool for plants and animals. Many plants are vital for medicines: 25 percent of conventional drugs used in the north originate from tropical forests. Quinine, the anti-malaria drug, curare, essential to modern anaesthetics, and the birth control pill all originated in South American tropical forests. Fifteen percent of Costa Rica's plants have potential anti-cancer properties. Extracts from an Amazonian tree called Castanospermine are being tested now as a drug against AIDS.

At present only eight plant species provide 85 percent of the world's food. If any of these is devastated by disease we must be able to turn back to tropical forests for new strains. Experts guess that the Amazon Basin alone contains about one million animal and plant species, including 2,500 species of trees, 1,800 species of birds and 2,000 species of fish, plus millions of insect species. Yet because most life exists in the forest canopy, which is still unexplored, no one in fact knows the true abundance of species; nor how many species deforestation is wiping out.

Who lives in the forests?

Tropical Forests are not unpopulated zoos or botanical gardens. They are the homes and territory of an estimated fifty million tribespeople—or were. There are about a thousand known forest tribes in the world and probably some undiscovered ones. Colombia alone has sixty tribal groups. The Philippines have seven million tribal people, Indonesia has 360 distinct ethnic groups, and 200 tribes live in the Congo basin. Papua New Guinea has over 700 tribes, mostly forest dwellers. Anthropologists estimate that 6-9 million people once lived in the Amazon basin. In 1900 Brazil had one million Indians. Now there are only 250,000. Since then at least one tribe has become extinct every year.

How does deforestation affect the climate?

The earth is wrapped in a blanket of protective gases, the most climatically significant being carbon dioxide. It lets the sun's shortwave radiation through but traps longer waved infra-red radiation (heat) keeping the earth warm enough for life to exist. A huge quantity of carbon is held in forest vegetation, and when forests are cut down or burned for land clearance, as millions of hectares are, the carbon is released into the atmosphere as carbon dioxide (CO2). Even rotting vegetation produces CO2. As the volume of atmospheric CO2 increases, so does the insulating effect on the earth, causing a rise in world temperatures: the "greenhouse effect." Forest burning in Brazil was responsible for about 20 percent of greenhouse gases released in 1988.

Locally, trees play an integral part in local climate through evapo-transpiration via their roots, trunks,and leaves. Half the Amazon's rainfall is recycled this way. Trees also stabilize the soil and diffuse falling rain with their leaf canopy, reducing soil erosion and increasing local humidity; and of course cloud formation over forests is itself a cooling mechanism.

The greenhouse effect has probably started already. Even a modest increase in temperature will cause a dramatic rise in sea levels: a rise of between only 0.6 to 1.0 degree Centigrade would drown London and Bangkok. Scientists have found that the amount of solar radiation being retained within the Earth's atmosphere is 0.1 percent more than twelve years ago.

How does deforestation cause flooding and droughts?

In recent years countries in the dry tropics have had worsening droughts, alternating with devastating floods. Forests control the run-off of rivers; typically 95 percent of rain reaching the ground is trapped in the soil by virtue of the elaborate spongelike network of roots in the forest floor, and then released slowly through the dry months When the trees are destroyed and the roots die, the soil dries and cracks in the hot sun, and water rushes off the land.Massive flooding results and precious top soil is washed into rivers. Tropical forests can receive in an hour as much rain as London expects in a wet month, and a single storm on deforested land has been found to remove 185 tonnes of topsoil per hectare. In February 1988, 300 people died in mudslides in Rio de Janeiro, Brazil, as a direct result of deforestation. In Thailand in 1988, 450 people died and property valued at $400 million was damaged following indiscriminate commercial logging. In 1978 in India a flash flood inundated 66,000 villages, killing 2000 people and 40,000 cattle. In Bangladesh in 1988 calamitous flooding was caused by deforestation in Nepal. In Sarawak, Malaysia, whole towns have been flooded. Deforestation also causes droughts because many tropical forest soils bake hard when exposed to the atmosphere and rain cannot permeate through to local aquifers (underground reservoirs). The world's rural population affected by serious desertification rose from 57 million people in 1977 to 135 million in 1984. 350 million more could be suffering by the end of the century.

What is the scale of the destruction?

In 1950, 30 percent of the earth's landmass was covered with tropical forest. By 1975 this figure was only 12 percent. In 1988 only 6 percent was left. Satellite photographs reveal that Brazilian forest is being lost at four times the rate previously estimated. By the end of 1988, 214,375 square miles had been deforested compared with 30,000 square miles a decade earlier. In 1988, 48,000 square kilometres of Brazil's tropical forest was burned—there were 8,000 separate fires in a single day, mostly illegal. Nigeria and the Ivory Coast will be completely logged out by the year 2000 and Costa Rica will have lost 80 percent of its forests. 80 percent of rainforest in Ghana has already disappeared as has one third of Malaysia's unique Sarawak rainforest. Every second about an acre of Brazilian tropical forest is burned: by 2000 Brazil will have lost an area the size of Portugal. Worldwide, an area the size of Britain is being logged out every year. That is 1 million acres a week, or 100 acres a minute. In fifty years the world's rainforests will be gone.

"There was once a rainforest in North Africa. Today we know the area as the Sahara."
(Jungle Stories, The Fight for the Amazon by Sting and J.P. Dutilleux, pub. Barrie & Jenkins, 1989)

What are the causes?

Destruction is caused primarily by the gigantic projects of multinational corporations: cattle ranches, paper mills, immense rice plantations, and by large-scale production of sugar cane, plantations for "gasohol" (fuel from vegetation), mining operations and pulping, and by dams and roads. At the other end of the scale is destruction by individual settlers: these often destroy the forest as efficiently as the large companies, because they operate illegally. In Brazil the law allows only half the trees on a parcel of land to be felled: illegal settlers strip the lot. Their position is pathetic. Many acknowledge that they are ruining the land and changing the local climate, but they have no choice. They may come from areas where landlords have prevented them using land or where soyabean monoculture (50 percent of which is exported to feed Europe's cattle) drives thousands of people from the land. Some come from slums in the large cities. They follow the new roads splitting the forests, and "improve" land so they can claim title to it. Many go from one clearing to another and then sell out to bigger estates, making a living out of land speculation.

Cattle ranching and plantations have laid waste millions of hectares of forest. In Central America cattle ranching is responsible for the clearance of about two thirds of the forests. Brazil's official government statistics reveal that 60 percent of forest destruction between 1966 and 1975 was caused by large-scale ranching schemes (3,865,271 hectares) and road building (3,075,000 hectares).

Dams too are a major cause of irreversible destruction.

"The crew of the spacecraft Discovery photographed a smoke cloud over the Amazon rainforest of a million square miles. Over Europe, it would stretch from London to Moscow." (Sun Telegraph 7 Days : 30.4.89)

[Extracted from "Tropical Forests: The facts you should know to save them," Ecoropa Information Sheet 17, available free at the PERC office.]

Converted June 9, 2000 - Lg

To follow up on this article, contact the author or the organizations/individuals mentioned; do not contact the Peace and Environment Resource Centre - we cannot provide follow up or contact information. This article is an archival copy of the printed one in the Peace and Environment News (PEN). Viewpoints expressed should not be taken to represent the opinions of the Peace and Environment Resource Centre, the PEN, or our supporters.

PEN Table of Contents
[ Search Home Contact ]