The loss of trees in our urban areas not only intensifies the urban heat-island effect from loss of shade and evaporation, but we also lose a principal absorber of carbon dioxide and trapper of other air pollutants as well.

Some of the major air pollutants mitigated by trees and their primary sources are:

• Carbon dioxide: Burning oil, coal, natural gas for energy. Decay and burning of tropical forests.
• Sulfur dioxide: Burning coal to generate electricity.
• Hydrogen fluoride and silicon tetrafluoride: Aluminum and phospate fertilizer production, oil refineries, and steel manufacturing.
• Ozone: Chemical reactions of sunlight on automobile exhaust gases. Ozone is a major pollutant in smog.
• Methane: Burning fossil fuels, livestock waste, landfills and rice production.
• Nitrous oxides: Burning fossil fuels and automobile exhausts.
• Chlorofluorocarbons: Air conditioners, refrigerators, industrial foam.

Managing and protecting forests and planting new trees reduces carbon dioxide levels by storing carbon in their roots and trunk and releasing oxygen into the atmosphere.