By John Strauss
Indianapolis, IN (May 16, 2008)- A recent study details the economic value of trees and the need to plant more. As a push to plant 1 million new trees across Indiana nears its halfway mark, a new study shows that trees provide an annual $5.7 million benefit in Indianapolis alone.
Researchers from the U.S. Forest Service evaluated more than 117,000 trees managed by Indy Parks and Recreation. They found that every $1 spent brought a $6.09 return in part through:
* Intercept 318.9 million gallons of rainfall a year at an estimated savings of nearly $2 million, or about $17 per tree, in stormwater handling costs.
* Cut electricity use by more than 6,447 megawatt hours, worth $432,000, by the shading effect of trees in the summer, which helps keep homes cool.
* Remove 1.5 pounds of air pollutants per tree, valued at $212,000.
* Increase property values and provide other benefits worth $2.9 million or, on average, $24 per tree.
Clarke Kahlo, a community environmental activist associated with the Marion County Alliance of Neighborhood Associations, said the study may help conservation efforts by showing the economic value of trees. “And besides those economic benefits, there are a number of studies that demonstrate trees provide high psychological comfort, a feeling of well-being,” Kahlo said.
The Indianapolis study comes four years after the start of a statewide effort to plant 1 million trees across Indiana sponsored by the Hoosier Heartland Resource Conservation and Development Council. Bob Eddleman, spokesman for the council, said about 450,000 trees have been planted. The state Division of Forestry also sells seedlings for conservation, including oak, tulip tree, walnut, white pine, ash and pine.
Greg McPherson, Director of the Center for Urban Forest Research and one of the study’s authors, said even more trees are needed. “Indianapolis citizens receive substantial environmental and aesthetic benefits from these trees, but the urban forest is at a critical juncture,” he said in a statement. “The city has many mature trees that need to be removed. In fact, tree mortality rates now outpace tree planting.”
“Indianapolis’ urban forest is uniquely diverse, with only one of over 170 species representing slightly more than 10 percent of the total tree population,” said Greg McPherson, Center for Urban Forest Research director and one of the study’s authors. “This diversity is important because it puts the forest at less risk of catastrophic losses from disease or pests.”
The total annual benefit of Indianapolis trees vary by species and size. For example, the city’s 16,371 silver maples produce the highest level of benefit at $60 per tree or 17 percent of the total citywide benefit. But, they are also the most expensive tree to manage because many are near the end of their productive lives and require removal or intensive care.
Scientists analyzed 2005 expenditures and found Indianapolis spends about $940,000 in a typical year planting new trees and maintaining existing ones. The biggest single cost and more than half the annual budget was for tree removal at $491,000, followed by pruning at $122,000. Overall, the annual return for the planting, care and management of the 117,525 trees in the study reached nearly $5.7 million.
McPherson said the city spends comparatively little on tree care at $8 per tree. This is less than half the 1997 mean value of $19 per tree reported for 256 California cities. It is also less than a quarter of the $25 per tree average for the 19 U.S. cities McPherson and his Center for Urban Forest Research colleagues previously studied.
“Indianapolis citizens receive substantial environmental and aesthetic benefits from these trees, but the urban forest is at a critical juncture,” McPherson said. “The city has many mature trees that need to be removed. In fact, tree mortality rates now outpace tree planting.”
The study cited in this article is a result of dollars spent by INDY Parks ($30,000) and the CUF Program ($20,000- grant dollars from the USDA Forest Service, Northeastern Area) for a total of $50,000. Indianapolis was the Reference City for the Lower Midwest region. The study was done to quantify benefits and costs for representative small, medium, and large deciduous trees in the Lower Midwest Region. This data can be directly correlated with the I-TREE Suite/STRATUM program so that municipalities in the region can quantify benefits, values and costs on their own tree populations from their tree inventories.
City of Indianapolis, Indiana, Municipal Forest Resource Analysis
Trees worth $5.7 million a year to Indy, study says- Indy Star
US Forest Service Pacific Southwest Research Station
Indiana Urban Forest Council
Indiana DNR, Division of Forestry
iTree and STRATUM