Developing Denver Needs Trees - how tree cover reduces costs for cities - Brief Article

American Forests, Summer, 2001

Ever wonder what a bunch of trees in a city are worth?

Consider this: Trees in Denver and in seven other Colorado cities are worth a total of $44 million in stormwater management--$3.2 million a year. Add another $5.3 million a year to factor in the removal of a couple million pounds of air pollution--stuff like sulfur dioxide, nitrogen dioxide, and carbon monoxide. Their value increases by another $4.5 million when you add the savings in air conditioning costs the trees provide through shade, a cooling system with an added benefit: no carbon emissions.

Those are among the findings of a new study AMERICAN FORESTS presented this spring to Denver's mayor, Wellington Webb, and to a number of the cities' foresters. The study was supported by the U.S. and Colorado State Forest Services, along with the forestry departments of the cities of Aurora, Boulder, Denver, Fort Collins, Greeley, Lakewood, Louisville, and Wheat Ridge.

Using satellite images collected in 1986 and 1998, AMERICAN FORESTS analyzed 425,000 acres around Denver and another 2-plus million acres from Denver to Fort Collins. Then, 39 sites were analyzed indepth with CITYgreen software.

The study found that over the 12-year period tree cover in the region increased just one percentage point (from 6 to 7 percent) while impervious surfaces increased three percentage points (from 9 to 12). In the Denver metropolitan area, tree cover increased from 4 to 6 percent, while hard-surface coverage increased from 30 to 39 percent.

"Colorado is a dryland ecology," said Gary Moll, vice president of urban forestry at AMERICAN FORESTS. "And with the rapid growth of population and urban areas here, it's vitally important to recognize the full environmental and economic value of urban trees. When impervious surfaces expand, tree cover needs to expand to compensate."

To take advantage of all the benefits trees provide communities, the study recommends cities along Colorado's Front Range plant trees at a rate that keeps pace with development. It also encourages city leaders, planners, engineers, and policy makers to take trees into consideration when making decisions about saving or developing land. See the full analysis at www.americanforests.org.