Trees for a Green LA
Program Advantages
Trees save energy and improve local climates. Strategically planted trees can:
• Help reduce overall air conditioning use and associated costs by up to 20 percent at homes and buildings.
• Shade outside air conditioning units, allowing them to operate 10 to 15 percent more efficiently than unshaded units.
• Provide shade that makes an attic 20 to 40 degrees Fahrenheit cooler on hot, sunny days, and walls about 15 degrees Fahrenheit cooler than unshaded walls, meaning less energy is needed for indoor cooling
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Many of modern life’s conveniences, and even necessities, can produce unfortunate side effects. For example, as growing numbers of computers, home electronics and appliances are used, more power generation is required, which in most cases increases air pollution. And, as more buildings and roadways are constructed, more hard surfaces are created that absorb heat, producing the “urban heat island effect” that radiates heat back into the environment and increases outdoor temperatures.
Urban areas are particularly susceptible to experiencing these effects; summer air temperatures are higher than in rural areas, air pollution is more concentrated and the landscape is significantly altered.
Trees, though, help solve these problems. Besides directly shading homes and buildings, and bringing more of nature’s harmony to the urban environment, trees counteract the urban heat island effect by absorbing and diffusing radiant energy from the sun, and by releasing water vapor into the air. Trees thus provide a natural cooling mechanism and create a much more pleasant atmosphere for all of our neighborhoods.
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Trees also reduce air and water pollution, help fight global warming, and conserve water. They:
• Lower the amount of air pollutants and greenhouse gases that come from electricity generation by reducing the need to use electricity to run air conditioners.
• Trap and absorb numerous pollutants (such as dust, ash, pollen and smoke) from the air.
• Act as a carbon “sponge” by removing the carbon from carbon dioxide (CO2, a greenhouse gas that contributes to global warming) and storing it in their trunks, while releasing the oxygen back into the air.
• Trap and hold up to 50 gallons of water each, lessening the stormwater runoff that causes flooding and pollution during the rainy season.
• Increase the amount of water filtered back into the ground, counteracting the effects of large areas of pavement.
• Reduce soil erosion and sedimentation in streams.
• Require, in many cases, minimal watering once mature, and help lessen the need to water lawns by providing the lawns with much-needed shade.
Trees enhance our neighborhoods and communities. They:
• Increase property values by 5 to 20 percent compared to non-landscaped homes, according to the International Society of Arboriculture.
• Establish more pedestrian-friendly areas.
• Add natural character to our communities and create more livable neighborhoods.
• Provide us with color and flowers.
• Create feelings of relaxation and well being.
• Provide privacy and a sense of solitude and security.
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An independent analysis of the Trees for a Green LA program, conducted by the U.S. Department of Agriculture Forest Service, shows that for every dollar spent, approximately $17.50 will be returned as avoided costs for energy supply and air pollution control. This total also takes into account the other environmental and social benefits associated with planting trees, such as increased property value and scenic quality, and improved human health and well being.
Additional findings of this analysis include:
• The average annual energy savings per tree planted will total 81 kilowatt-hours – enough energy to keep a typical TV on 24 hours a day for almost 17 days (400 hours total).
• Each tree planted will prevent 1,500 gallons of stormwater runoff each year.