City trees can reduce energy use for heating and air conditioning buildings, according to urban forestry expert Greg McPherson. Properly sited trees can reduce temperatures in urban areas by 2-8 degrees Fahrenheit (1-4 degrees Celsius). By reducing energy use, these trees reduce demand for electricity and reduce carbon dioxide emissions from power plants. Trees also remove carbon dioxide from the atmosphere directly. The Western Center for Urban Forest Research and Education, led by McPherson, has studied the costs and benefits of the urban forest in California cities including Sacramento, Modesto and Santa Monica. The center worked with the Sacramento Municipal Utility District to evaluate their shade-tree program. "It was cheaper for SMUD to plant trees than to generate the extra energy," said McPherson. The center is a field laboratory of the Pacific Southwest research station of the U.S. Department of Agriculture Forestry Service. More information: .