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Urban Study Confirms Trees are Cool: Trees are Cost-Effective and Pleasant Way to Cool Our Cities

Release Date: 04/10/2003
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(#03031) Trees can significantly cool urban areas that generate heat and clean the air by absorbing pollution, according to two studies sponsored by the U.S. Environmental Protection Agency (EPA) and the New Jersey Department of Environmental Protection (DEP). The studies examined so-called "urban heat islands" surrounding the cities of Newark and Camden and explored various measures to mitigate their adverse effects. On warm summer days, the air in urban areas can be significantly hotter than in surrounding areas an effect called a "heat island." The problem is caused by a variety of factors that trap heat, including buildings and dark pavement that absorb the sun's rays rather than reflect them. "These two cities generate unneeded heat, which is not only unpleasant, it can have real health consequences for urban residents and for the environment," said Jane M. Kenny, EPA Regional Administrator. "The good news is that there is a relatively simple and economical solution plant trees." Kenny added that while it can take five years or more for a newly planted tree to grow enough to begin significantly cooling the environment and absorbing pollution, the long-term benefits of trees are irrefutable. "Johnny Appleseed had it right," said New Jersey DEP Commissioner Bradley M. Campbell."These studies reinforce the need for Governor James E. McGreevey's initiatives to plant 100,000 new trees in New Jersey's urban and suburban communities." Campbell noted that theDEP already has begun planting more trees in Camden using $1 million funded by a supplemental environmental project. In the short term, Kenny pointed out, there are additional steps that can be taken to reduce the"heat island" effect. These include constructing buildings using the principles of EPA's Energy Star program, which can conserve energy and reduce demand and the pollution that comes with generating electricity. The two studies conducted by Montclair State University and National Aeronautics and Space Administration's Goddard Institute for Space Studies with research assistance from Columbia University confirmed that both Newark and Camden have heat islands. The average air temperature in Newark can be as much as 11 degrees Fahrenheit higher than its suburbs and Camden's temperature can top the surrounding area by as much as 6 degrees Fahrenheit. This increase in temperature is bad for many urban residents' health. Hotter weather increases the frequency of heat-related health problems, such as heat exhaustion, and induces more asthma attacks, as the heat concentrates air pollution and speeds up smog formation. In addition, higher temperatures result in more expensive utility bills as residents run their air conditioners longer. The New Jersey studies point to tree planting as a key strategy in combating urban heat islands in the future. Trees serve numerous purposes. In addition to providing shade from the sun, trees absorb carbon dioxide and filter out pollutants from the air. They cool the air by excreting droplets of water that draw heat as they evaporate, which is a process called"evapotranspiration." Trees also absorb sound, prevent erosion and provide habitats for birds and animals. "Trees also provide an attractive canopy for urban areas, making communities more attractive to business and tourism, transforming a neighborhood's appearance and increasing home market value, as they bring nature closer to where we live and work," added Campbell. The studies also showed that heat islands can be tempered by using lighter colored or more reflective surfaces on buildings, roofs and streets.