Forest fires contribute to air pollution by emitting carbon dioxide, methane and other trace gases into the atmosphere. Wildfire management in the United States costs up to 1 billion dollars per year. Despite the use of radio communications, rapid helicopter transport, and new types of chemical firefighting apparatus, about 4 million acres of U.S. forest burn in a typical year. Roughly half of this total is a result of fires caused by lightning. However, 90 percent of all wildland fires are caused by humans, whether intentionally or by accident. Because fire suppression can lead to a long-term buildup of fuel, researchers and forest managers are exploring ways to use controlled burns, mechanical thinning, and other means to restore the health of overgrown forests.
