Q & A: How Many Pounds of Carbon Dioxide Does Our Forest Absorb?

Q. My family owns a 40-acre woodlot of relatively mature deciduous trees. How many pounds of carbon dioxide does such a forest absorb in a typical year? And how many pounds of oxygen are emitted?

A. "An approximate value for a 50-year-old oak forest would be 30,000 pounds of carbon dioxide sequestered per acre," said Timothy J. Fahey, professor of ecology in the department of natural resources at Cornell University. "The forest would be emitting about 22,000 pounds of oxygen."

"Every little bit matters," he said. "In the grand scheme of things, forests in the northeastern United States are counteracting a considerable amount of fossil fuel burning by cars, slowing down the rate at which the greenhouse gas carbon dioxide is accumulating in the atmosphere."

The contribution varies with the age of the forest and the species involved. There is no real rule of thumb on the difference between conifers and deciduous trees, Dr. Fahey said. Some conifers grow faster, providing more impact sooner.

The Environmental Protection Agency has calculated the amount of carbon dioxide emitted by the average car as of 2007 at about five metric tons, more than 11,000 pounds, so a single acre of woodlot would be countering the emissions of about 2.7 cars. For 40 acres, that would be about 109 cars.

This article has been revised to reflect the following correction:

Correction: December 6, 2012

An answer in the Q&A column on Tuesday about the amount of carbon dioxide absorbed by forests miscalculated the amount of carbon dioxide an acre of woodlot absorbs, expressed as a number of average cars. A single acre of woodlot would counter the emissions of about 2.7 cars, not about 0.37 cars. For 40 acres, that would be about 109 cars, not 15.