Carbon in its element

Science News, Feb 3, 2001 by S. Perkins

The article "Banking carbon in trees and other plants" (SN: 12/16/00, p. 397) did its best to downplay trees as a sink for carbon dioxide with hocus-pocus science and computer modeling. Let me present a commonsense picture. Once carbon is in wood, it will stay there until the wood rots or burns. I agree that cutting back fossil fuel use is the major issue. But wood products--lumber--help by sequestering carbon while replacing steel, concrete, and plastics, the manufacture of which is more fossil fuel intensive.

Chuck Phegley

Baker City, Ore.

Adequate levels of carbon dioxide are every bit as vital to survival of life as are levels of oxygen, and it is perhaps man's only beneficial purpose to ensure adequate levels of carbon dioxide through recycling buried carbon. Without recovery of buried carbon to counter nature's propensity to bury it, Earth would inevitably be uninhabitable by life as we know it.

McClellan Blair

Indiana, Pa.

The article on carbon dioxide sequestration contains a puzzling statement, attributed to Richard Betts of the Hadley Center for Climate Prediction and Research. It's to the effect that absorption of solar radiation by foliage could result in an increase in local temperature. I thought that solar radiation absorbed by plants was for photosynthesis, resulting in a transfer of radiant energy from the sun to the latent energy of plant tissue, thus reducing the amount of radiant energy available for heat. This cooling effect of foliage is a positive aspect of plant growth that I have never seen put into the energy-balance calculations. In simple terms, a net increase in biomass should mean an increase in the amount of solar radiation diverted to energy reserves.

Leonard Stoloff

Delray Beach, Fla.

Energy stored in plants by photosynthesis is temporarily sequestered in the food chain, says Betts. However, he adds, photosynthesis is notoriously inefficient. About 99 percent of the energy physically heats up the plants, and this eventually either warms the air, evaporates water on or within the leaves, or is conducted into the ground. Betts says that most realistic computer models of climate--including the one he used in his analysis--do account for the local effects of heat transfer. He notes that much of even the 1 percent of solar energy that is chemically stored in the food chain eventually returns as warmth.