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Planting the Roots of Success |  |
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| By: MIKE DOMBECK, Tampa Tribune - | |||||||||
| Spring is a good time for the two important environmental events that took place this past week, Earth Day and Arbor Day. We know that water, sun, soil and air make plants grow. But while we celebrate Earth, other important connections between plants and the environment should be better appreciated, especially in Florida. America's cities, suburbs and towns cover nearly 100 million acres of mostly former forestlands -- roughly half the area of our national forests. Between 20 and 25 percent of our urban areas remain wooded and many cities lie on forest edges. But, with only one tree planted for every four removed within cities and sprawl consuming 9,000 acres a day, these numbers are changing. In Florida they are changing rapidly. Florida�s population swelled from less than 3 million in 1960 to 17 million today. By comparison, Michigan, with about the same area, saw its population grow from roughly 8 million to 10 million during the same period. By 2030 Florida�s population will approach 25 million. Already, 10 percent of Florida�s landscape is urban, about twice the lower 48 states� average, and by 2030 it will be 20 percent. This is unfortunate because trees provide "ecological services" that make our cities more livable. Forest vegetation and soils combine to produce abundant, quality water. Two-thirds of the runoff in the contiguous 48 states flows from forests, which cover only a third of the land. Cities near forests benefit from these services. New York City, for example, has some of the best water in the world because of its forested watersheds, which keep New York exempt from expensive filtration requirements. Trees within cities are good too. If unimpeded, water rushes quickly over hard surfaces directly into streams, leaving little to soak into the ground. More runoff means more contaminants entering streams. Trees and shrubs intercept rain, slowing its arrival to the ground. There, it filters through soils into aquifers. Excess ground water -- now pure -- seeps continuously into surface water, affected little by all but the worst droughts. This becomes problematic in Florida, where its many limestone caverns collapse with greater frequency when water is used faster than it is replaced. In many cities, stormwater and sewage systems are often connected, outdated and inadequate to handle peak flows. Heavy downpours and prolonged rains frequently result in flooding and the discharge of raw sewage into waterways -- a process exacerbated in cities with a high percentage of hard surfaces. |
Trees can help minimize these problems. The American Forests organization estimates that trees reduce stormwater runoff by 15 percent in parts Miami. Yet because Miami has less than 20 percent tree cover, and nearly 60 percent of the city consists of pavement and buildings, the stormwater benefits of trees could be vastly increased. Similar numbers are not available for Tampa, but we know that the urban area has a tree cover of about 19 percent and that the suburban fringe saw its tree cover decline from 67 percent in 1975 to 47 percent in 1996. Tampa ranks eighth nationally in sprawl during the past three decades. Numbers from other cities suggest Tampa�s trends are costly. Tree loss in Atlanta between 1974 and 1996, for example, resulted in a 33 percent increase in runoff during heavy rains. Trees also improve air quality by removing pollutants. This is good news because we now know that particulate air pollution is responsible for up to 7 percent (and much more in some cities) of cardiopulmonary deaths in the U.S., according to the Natural Resources Defense Council. The World Health Organization found that mortality rates increase as much as 20 percent on days with severe pollution in parts of Europe. Although emissions must be reduced, more trees would help. The U.S. Forest Service estimates that Chicago's trees, which currently cover only 13 percent of the city, annually eliminate some 650 tons of air pollutants, saving the city about $9 million annually in air pollution services. In Atlanta, with more tree cover, the number is about $47 million. By lowering summer temperatures, trees also save on energy. Our estimates at the University of Wisconsin-Stevens Point suggest that if tree planting were optimized across America, combined with existing tree cover, that the savings would equal the energy produced by 120 100-megawatt power plants. In energy units, that�s about 60 million barrels of oil. Miami could save 20 percent just by replacing palms with live oaks. Trees are of course no substitute for technological fixes to urban woes, but should be more central to urban environmental management. American cities have room for perhaps 700 million trees according to the U.S. Forest Service. On average, tree cover could be doubled in U.S. cities, and more so in many Florida cities. Ultimately, trees do more than make cities look good--they measurably and significantly contribute to city life, and people are often willing to plant them. Moreover, the benefits come without sacrifice, start-up costs are low and the rate of return is quick. As the nation debates pollution, sprawl, and energy, tree-planting campaigns should be expanded. |
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� 2004 GEM Education Center - UWSP 800 Reserve Street, Stevens Point, WI 54481 ph. (715) 346-4122  |
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