Amazon forest facing the axe

Posted: 19 February 2002

Within a decade, there could be no more tropical rainforests to save, warns an American environmental researcher. The problem lies in the interactions between direct threats such as logging and mining, climate feedback that could bring far less rain to the remaining fragmented forests, and loss of essential species that help sustain the rainforest ecosystem.

Using the two million square mile Amazon River Basin as an example, Professor James Alcock said his research shows that if there is no immediate and aggressive action to change current agricultural, mining and logging practices, the rainforest could pass "the point of no return" in 10 to 15 years.

Working from his office on the Penn State Abington campus, Alcock, professor of environmental sciences, has developed a mathematical model to study the effect of human driven deforestation. Current deforestation rates of about one per cent per year in the Amazon River Basin rainforest in Brazil could push the rainforests past the point where they can sustain themselves within a decade, Alcock argues.

The other key tropical rainforests are in the Congo River Basin in Africa and Southeast Asia.

Rainforests are dependent on high levels of precipitation brought on by daily rain, and a healthy forest holds onto the rain and returns it to the atmosphere so it can be recycled - a process called evapotranspiration. Without a healthy base of vegetation, water runoff occurs at a higher rate, and it creates the potential for a highly unstable rainforest system.

While others have studied the effect of tropical rainforest deforestation on regional and global climates, Alcock said his study differs because it focuses on the local impact of the issues. In the Amazon River Basin, for example, loss of the forest would probably cause the extinction of many species of animals.

These species not only depend on the rainforest, Alcock said - the rainforest also depends on its wildlife. For example, insects are needed to pollinate flowers and recycle fallen foliage, while many birds and small mammals are required to spread the seeds of vegetation to help new trees and bushes to grow in clearcut areas.

"There are already a large number of species that are endangered, because the forest itself is endangered," said Alcock. "We might be able to keep a few animals at the zoos, but we'd surely lose a lot of amphibians, reptiles and insects. We couldn't take them all."

Alcock's model indicates that the rainforest could essentially disappear within 40 to 50 years. That is a far cry from the common belief among researchers that the forest is still 75 to 100 years away from total deterioration, if current patterns prevail, said Alcock.

"Because of the way tropical rainforests work, they are dependent on trees to return water to the air," said Alcock, noting that the sheer size of the Amazon River Basin has already been reduced by about 25 per cent.

"This interdependence of climate and forest means risks to the forests are much closer at hand than what we might expect, and we're doing very little because of the priorities of Brazil and The Congo," Alcock noted. "It's a very difficult problem because of several pressures. For example, you cannot say, 'leave the rainforests alone' when people are living in poverty."

There are those who espouse preserving small portions of the rainforest, but Alcock said damage to the overall system would probably limit the rain necessary to do that. Less rain could also mean more forest fires, further threatening the balance of the rainforest.

This was a slightly shortened version of an Environment News Service report, June 2001.