Tropical Forests Recover From Clear-Cutting

Feb. 18, 2009 -- Deforestation is generally considered to be bad news, especially in the tropics. But there may be some hope: In many places, trees are growing back, according to new research, and some of the new forests are nearly as diverse as the old ones were.

The work adds to a growing sense that tropical forests are more resilient than scientists previously thought and that second-growth forests are far from worthless.

"When I started out, if you picked up an ecology textbook, it would say that once a tropical forest was cleared, it would never grow back," said ecologist Robin Chazdon, of the University of Connecticut in Storrs. Her work is helping rewrite the books. "I view it as a hopeful message."

As much as 60 percent of the world's tropical forests have been cut or burned, primarily to make way for pastures. But now, even as deforestation continues at an alarming pace, an increasing number of pastures are being abandoned as a result of conservation efforts, changes in crop prices, even war.

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In temperate regions such as New England, studies show that mature forests have successfully reclaimed many abandoned fields over the last 100 years. But much less is known about re-growth in tropical places, partly because hundreds of tree species can live in one small area of the tropics (compared to a dozen or so in New England), making research challenging.

For nearly 20 years, Chazdon has been working in Costa Rica to see how new forests compare to old ones. In her studies, she has attempted to identify all tree species in relatively large plots of forest. Her plots include both pristine, old-growth areas and newer, second-growth forests that have only recently overtaken abandoned pastures.

At a recent biodiversity symposium in Washington, D.C., Chazdon reported encouraging results. She has found that, after just 20 or 30 years, second-growth forests can have just as much biomass as old-growth forests do. Biomass is a measure of the total plant life in an area.