Loss of Amazon Rain Forest May Come Sooner Than Expected

National Geographic News
June 26, 2001
EDINBURGH, Scotland—While many environmental issues today are
highly contentious, there's one cause that seems to unite nearly
everyone: pleas to save the world's rapidly disappearing rain forests.
Yet a new mathematical model suggests we may not be acting fast enough.

According to projections by a Penn State professor, Amazonian rain forests could reach a "point of no return" in as little as 10 to 15 years from now if deforestation continues at the present rate of about one percent a year.

The model further shows that rain forest in Brazil could be wiped out entirely within 40 to 50 years—much sooner than predicted in other studies, which have led many researchers to estimate that total rain forest loss won't happen until the end of this century, 75 or 100 years away.

James (Bud) Alcock, a professor of environmental sciences at the Abington campus of Penn State, reached these conclusions by constructing a mathematical model that used the two million-square-mile Amazon River Basin as an example.

Because moisture is critical to rain forest ecosystems, Alcock studied how the ecosystem responds to changes in natural climate cycles that occur over time when large areas of trees and vegetation are cleared for agriculture, logging, and mining.

"Because of the way tropical rain forests work, they are dependent on trees to return water to the air," he said, adding that about a quarter of the total rain forest in the Amazon River Basin has already disappeared.

The results showed that, with no action to curb the losses, the rain forest could become unsustainable—that is, unable to regenerate and thrive fast enough to maintain its unique ecosystem and the life it supports—within the next decade or so.

Alcock presented his findings June 25 at a joint conference of the Geology Society of America and the Geology Society of London in Edinburgh, Scotland.

Climate-Forest Connection

"The interdependence of climate and forest means risks to the forests are much closer at hand than what we might expect," said Alcock.

He explained: Rain forests require high levels of precipitation, which comes from rain. A healthy forest takes in that rain and returns it to the atmosphere so it can be recycled (a process called evapotranspiration).

Without a healthy base of vegetation, there is greater runoff of water. This upsets the balance of water circulation, which over time is likely to make a rain forest highly unstable.

Alcock disagrees with people who argue that the essence of the rain forest and its unique ecology can be maintained by preserving small sections of the rain forest. Damage to the overall system would probably limit the rain necessary to do that, he argues.

Less rain also means greater vulnerability to forest fires, further threatening the balance of the rain forest.

No Easy Solutions

Many other researchers have studied the links between tropical deforestation and climate change. Alcock said his study differs from most of that work because he focused on how altered weather patterns affect rain forest ecosystems at the local level, rather than studying the interrelationship of tropical deforestation and regional or global climate.

In the Amazon River Basin, Alcock noted, the loss of large areas of forest is likely to bring about the extinction of many species of animals that are dependent on a healthy forest environment.

"There are already a large number of species that are endangered because the forest itself is endangered," he said. "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."

Halting deforestation is a tough issue for society to address because millions of people living in and near the major remaining rain forests of Brazil, the Congo, and Southeast Asia are heavily dependent on the forest for their livelihood, Alcock noted. "You cannot say 'Leave the rain forests alone' when people are living in poverty," he said.

Although Alcock conducted his model-based study at Penn State, he said he hopes to extend the research through field work in the Amazon Basin.

He undertook the present study as a way to better explain the concept of feedback—exemplified by precipitation and evapotranspiration in the rain forest—to his students in an introductory course on earth systems.

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