Denver Post.com - Savings grow on trees along Front Range By Theo Stein Denver Post Environment Writer Wednesday, April 18, 2001 - The Front Range's urban forests do a lot more than just sit around looking pretty, a new report by American Forests shows. The entwined root systems and leafy canopies of urban trees in the seven largest northern Front Range communities combine to act like a $44 million regional stormwater management system and remove 2.2 million pounds of pollutants annually - including ozone, carbon monoxide and fine sooty particles, the group said. The cooling shade that trees cast also saves homeowners an estimated $4.5 million in annual air conditioning costs, or about $50 per household. This, in turn, prevents the emission of 1.6 million tons of carbon gases from power plants, the group estimated. But the study, based on a comparison of satellite photos taken in 1986 and 1998, also suggests that the growth of the region's urban forests isn't keeping pace with galloping development of impervious surfaces such as roofs, driveways and parking lots, and newly planted subdivisions. The report, which is being released today, seeks to impress on city managers and decisionmakers that trees are more than just something good to look at. A news conference is scheduled for 10 a.m. at The Waring House, on York Street near the Denver Botanical Gardens. Air filter, sponge, humidifier, heat shield, wind block, carbon sink: trees are the ultimate urban multitaskers, said Gary Moll, vice president of American Forests' Urban Forest Center. "We want people to understand that trees are an important part of the city infrastructure," he said. "There's a hard part, and there's a green part, and we should be planning for both." Local officials acknowledge that the ecosystem values cited in the report are just estimates. The study was based on findings from 39 representative plots, which were then extrapolated. Denver's urban forester thinks the report is "on the money." "Finally, we have a way to quantify the benefits that trees provide," said Jude O'Connor. "We can give them a dollar value, not just say that they're "nice' and they soften hard edges of the urban landscape." O'Connor said it's logical that in the arid regions of the West, the growth of concrete, which can be installed in a day, will outstrip the growth of trees, which take decades to mature. "There will always be a lag in the system," she said. "Out here, we're creating our forests and moving out," said Philip Hoefer, the acting assistant state forester. "It was only 140 years ago that we started growing this landscape." Traditionally, trees have been appraised like a piece of real estate and assigned a value based on their replacement cost. But American Forests uses a computer model to evaluate trees' physical functions and estimate the total services provided. The Front Range's arid landscape, which is naturally dominated by drought-tolerant grasses, provided a challenge for American Forests modelers. Previous studies focused on coastal cities, including Houston, Seattle and Washington, D.C. The Front Range study was the first to tackle a dry-land interior climate. "The biggest difference is there's no natural tree cover," said Moll. "So we had to use an entirely different technique and rely on local people to make sure we were making correct assumptions." The report shows that in Denver, Westminster, Lakewood and Aurora, the amount of land covered by impervious, or water-shedding, surfaces grew from 125,500 acres to 166,000 acres, a gain of 32 31 percent. By contrast, forested areas grew nearly 45 percent, almost doubled in size? from 18,000 acres to 26,000 acres. But even with that jump, trees covered a mere 6 percent of the four cities' total acreage, while 39 percent has been paved over. The bigger picture isn't much different: 32 percent of the 275,000 acres included in the Front Range survey were covered by an impervious surface, while 7 percent is forested. The regional study looked at the four metro Denver cities, plus Boulder, Fort Collins and Greeley. The report also highlighted dramatic changes in the amount of grassland and cropland. The metro area saw a 22 percent erosion in the amount of irrigated cropland from 1986 to 1998, while across the Front Range the drop was 33 percent. O'Connor, who must care for 200,000 city trees with only 25 staffers and a budget of $2.5 million, said the report helps to demonstrate that urban forest management has to be looked at as an ongoing process. "Many trees in our older neighborhoods are overmature and declining," she said. "Eventually, they'll have to come out, but the key piece is to get back in there and replant. "Their report confirms we've done a good job planting trees, but it shows in older neighborhoods we're not keeping pace with mortality. And there's an economic factor. When you lose trees in affluent neighborhoods, people replant. In poorer neighborhoods, they don't." Hoefer said the report will also give urban foresters valuable baseline data as well as an economic argument to encourage developers to think green. "Trees can have a major effect on energy use in homes," he said. "New homes are going to use a lot of energy because they're sitting out there in barren wasteland. But if you put an air conditioner in the shade of a tree, it makes the machine 10 percent more efficient. On individual basis, that might not seem like much, but when you multiply that by 500 homes in a subdivision or 5,000 homes in a community, it begins to add up." 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