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Slower Growth, Greater Warmth

A shift toward slower-growing trees might make Earth's climate warm up even faster.

There seems little doubt that Earth is heating up. As temperatures rise, many people worry about how global warming may affect life on the planet.

A long-term study in Central America gives one more reason for concern. Adult trees in a rain forest in Costa Rica grew more slowly in warm years than they did in cold ones. Such a shift toward slower-growing trees might make the climate warm up even faster.

View across the forest canopy at La Selva in Costa Rica.

View across the forest canopy at La Selva in Costa Rica.

Alan Campbell/Oak Ridge National Laboratory

From 1984 to 2000, biologist Deborah A. Clark of the University of Missouri-St. Louis and colleagues measured the width of old trees in a 2-square-kilometer plot of rain forest at La Selva, Costa Rica. During the coolest years, a time period running from 1984 to 1986, the trees grew 81 percent faster than they did during a heat wave that struck in 1997. The trees also grew slowly in 1987, another warm year.

In addition, scientists found that, during warm years, Earth's atmosphere contained less carbon dioxide produced by tropical land plants. Carbon dioxide is a heat-trapping gas, which plants normally use up to make food.

The new results reinforce how important trees are to the health of the planet and how devastating a continued rise in temperatures might be to their future—and ours.—E. Sohn

Going Deeper:

Perkins, Sid. 2003. Feel the heat: Rain forests may slow their growth in warmer world. Science News 163(April 26):260. Available at http://www.sciencenews.org/20030426/fob3.asp .

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