Amazon forests fall and climate begins to change

Climatologists have long been concerned that cutting of the Amazon forest may change the region's climate. Now the first evidence is in. Increased flooding of the upper Amazon basin indicates that such a climate change may have started.

In a recent report in the journal Science, a. H. Gentry of the Missouri Botanical Garden at St. Louis and J. Lopez-Parodi of the Proyecto PARI Jenaro Herrera research project at Iquitos, Peru, call attention to a change in the regional water balance which they say, "appears to be the result of increased runoff due to deforestation."

"If so," they add, "the long-predicted regional climatic and hydrological changes that would be the expected result of Amazonian deforestation may already be beginning."

The area of concern is the largest tropical rain forest left in a world where such forests are rapidly disappearing. Clearing large slices of these forests for roads, housing, industry, and similar developement exposes the land to increased runoff and erosion.

This process can eventually lead to a drier regional climate.Unlike an area such as the North American Great Plains or Western Europe, where most of the precipitation represents moisture blown in from the sea, something like half of the Amazonian rainfall is water that is recycled within the basin.

Trees take up moisture that falls and send it bak into the air --recycling could be curbed to a degree that "might eventually convert much of now-forested Amazonia to near desert," Drs. Gentry and Lopez-Parodi warn.

a key deforested area has developed along the edge of the mountains in upper Amazonian Ecuador and Peru during the past 10 years. the Two scientists find increased runoff from this area during the last decade -- in spite of there being no significant changes in regional rainfall patterns.

Furthermore, they find that annual high water levels in the Amazon have been consistently and significantly higher since 1970, although the low water levels have not changed.

The scientists warn that, since population and farming are concentrated along the seasonally flooded river margins, "the magnitude of the damage is potentially great." They add that "the rapidity with which relatively limited forest destruction appears to have altered the Amazonian water balance suggests the need for planned development. . . ."