left much unanswered or ambiguous. For example, American Forests recom- mends that a city have a UTC of 40% but could not detail how their UTC recommendations had been derived.
In light of scientific data on the relationship between UTC and stream health, AES explored four scenarios for pos- sible UTC increases that would all achieve a level of coverage associated with a stream health ranking of "good" to "excellent." The study by UVM generated data on the maximum poten- tial UTC that could be achieved within specific land use areas and city- wide. Our study looked at incremental increas- es of 10, 15, and 20% in all land uses, and 20% in the housing land use only. For each goal, we projected the number of trees to be plant- ed, associated planting costs, and increase in tree-covered acreage. Assumptions as to the natural mor tality of urban/suburban trees, growth rates, the willing- ness of property owners to plant trees on their
We then researched various approaches to set- ting UTC goals, including comparisons of local and regional goals and recommendations from national environmental groups, and reviewed the scientific literature on the relationship between UTC and stream health. While this approach yielded significant amounts of data, it also
www.urban-forestry.com
property, and the fiscal restraints of the munici- pality were factored into the analysis.
The graphic at left shows that, for example, if the City of Bowie adopted an increase in tree canopy that represented 10% of the possible UTC, it would have to plant 20,270 trees at a cost of $202,704. City planners can use this
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