May 1999 - Vol. Many benefits are quantifiable. Evergreen trees block winter winds and can save 20 percent on a home's winter heating needs. One acre of trees can remove 40 tons of carbon dioxide, a gas that contributes to global warming, a year. One acre of trees annually produces enough oxygen to sustain more than 1,000 people.
Trees reduce stormwater flow by intercepting rainwater on leaves, branches and trunks.
Some of the intercepted water evaporates back into the atmosphere, and some soaks into the ground, thereby reducing the total amount of runoff that must be managed in an urban area. A medium-size tree can absorb up to 400 gallons of water a day. Energy savings of 10 percent can result by increasing tree cover as little as 10 percent to buffers near buildings. If live oaks were put in place of palms, those savings would increase 20 percent. A single mature tree releases about 100 gallons of clean water vapor per day into the atmosphere and provides the cooling equivalent of nine room air conditioners operating at 8,000 BTUs per hour for 12 hours a day.