Carbon dioxide may spur plant predation.

Carbon dioxide may spur plant predation 

Plants grow faster in air containing double today's carbon-dioxide levels--an atmospheric increase expected within the next century. However, this "carbon dioxide fertilization" results in more carbohydrate-based tissue and less protein in the plant -- a condition expected to limit insect growth and perhaps vitality. Three studies now confirm adverse effects in insects eating plants grown at doubled levels of carbon dioxide.

Buckeye-butterfly larvae dining on such plants ate about 15 percent more than their counterparts eating plants grown at today's carbon dioxide levels, took 10 percnt longer to reach pupation and were visibly weaker, report ecologist Eric Fajer and his co-workers at Harvard University.

David E. Lincoln at the University of South Carolina at Columbia found that cabbage-butterfly larvae dining on plants grown at double the ambient carbon dioxide level needed 43 percent more food to maintain the same growth as larvae eating plants raised at current levels. And he found that sagebrush-eating grasshoppers needed 36 to 58 percent more food if dining on plants raised at high carbon dioxide levels.

It remains unclear, Lincoln says, whether a plant's increased growth under carbon-dioxide-rich conditions would compensate for this greater predation.