How much are trees worth to city? A lot

By Spencer Heinz
Portland, OR (October 3, 2007)- In tree-friendly Portland, lots of people figure green is good. How good? The city has put a dollar figure on it. After months of data crunching, the City Nature Urban Forestry division of Portland Parks & Recreation concludes that the theoretical replacement value of Portland’s public and private trees would be at least $5 billion.

Analysts say that reflects trees’ worth in terms of everything from cutting pollution to improving property values. Armed with figures like that in a just-finished report titled “Portland’s Urban Canopy,” city forester David McAllister is expected to go to the City Council today to recommend increasing the city’s amount of tree planting, tree maintenance and public education.
“We take our trees for granted,” McAllister says. “Everybody likes them. They’re green. Portland considers itself a livable city. But nobody understands the hard work these trees are doing. They provide a direct economic benefit to every citizen in Portland.”
For those who want to know those benefits, he flips through pages of facts such as these:
* Tree canopy covers about one-quarter of Portland- 26 percent.
* The public part of Portland’s arbor cover- the estimated 1.4 million trees in city parks and along city streets- has an estimated replacement value of $2.3 billion.
* The other part of Portland’s canopy- uncounted numbers of trees on private properties- has an estimated replacement value of $2.7 billion.
* Annually, the city says, those public trees cost about $6.6 million to manage while providing some $27 million of aesthetic and environmental benefits.
Trees do that, the analysts say, by reducing needs for natural gas and electricity, removing some air pollutants, keeping much storm water from reaching overburdened city sewers, and by reducing an earth-warming greenhouse gas, carbon dioxide. In sum, the report says, for every dollar invested in Portland’s public trees, those trees return $3.80 in benefits.
The idea of fastening a price tag on the functions of trees, parks officials say, is a way of asking what would happen if the trees disappeared. The idea is to calculate how much it would cost for machinery and more to try to replicate what trees provide naturally.
“What we’re suggesting is that the ‘green’ infrastructure is just as important as the gray infrastructure- roads, buildings, bridges,” says Jennifer Karps, a botanic specialist with the bureau. “We want to raise people’s awareness of trees not just because we like them and they’re pretty, not just for the aesthetic benefits, but for the ecosystem services that they provide.”
Karps said the City Nature Urban Forestry division estimated Portland’s tree-replacement costs by considering sizes, locations, species and conditions of Portland’s street and parkland trees according to nationally recognized methods of the Council of Tree and Landscape Appraisers.
Putting dollar amounts on trees, McAllister says, helps change forestry from reactive to proactive in terms of maintaining healthy trees. The city’s oldest trees, he says, provide most of the environmental and aesthetic benefits.
Mark Derowitsch, spokesman for the Nebraska-based Arbor Day Foundation that encourages people nationally to plant and celebrate trees, says he supposes he can see how cities might want to say how much those trees are worth. He says they certainly help a great deal. But saying how much, he says, is hard.
“Because trees are priceless,” he says. “It’s sort of like asking someone to put a dollar value on a trusted friend.”
For the full article, visit The Oregonian.
Related Resources:
Friends of Trees