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Ecosystem Services in the City of Denton, Texas Comprehensive Plan Area |
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| William Forbes, Dwight Q. Barry, J. Baird Callicott, Kenneth L. Dickson, | |||
| Session: | Author Info | ||
Urban trees and greenspace are at risk. Population growth rates in the Dallas-Fort Worth metropolitan area, where Denton is located, are among the highest in the nation (up to 6% annually). Many new residents move into low-density housing. The University of North Texas is providing the City of Denton with a method for systematically identifying, evaluating, and synthesizing the various environmental attributes and services associated with urban trees and greenspace. This paper describes tasks included in the project.
Developing and refining evaluation criteria
Examples of values provided by the four primary local habitats, upland cross timbers forest, upland prairie, wetlands, and bottomland hardwood forest, include: ecosystem services such as air and water quality mitigation, stormwater treatment and flood control, recreation, fish and wildlife habitat, enhanced property values; and ecological goods such as scenery, heritage sites, and core and connecting habitat for native species (aesthetic, historical, and intrinsic values).
For each habitat area, each of the ecological values is rated good, moderate, or poor based on specific criteria. Need for rehabilitation (services) or restoration (goods) can be evaluated based on ratings for individual habitats. The best local habitats (bottomland forest, native prairie, cross timbers) were field rated 0.7 to 0.8 on a scale of 1.0. Lower quality local habitats (parking lots, residential streets, abandoned crop fields) were rated 0.3-0.5. The criteria will be further refined to incorporate soil values. A handful of primary sources were used to develop the rating system format and critera (Canter 1995, Costanza 1998, Johnston 1989, Murray et al. 1991, Morgan and Tolisano 1998).
Additionally, a paired ranking analysis was completed. Results correlated with a study indicating that bottomland hardwoods were the most valuable local habitat for ecosystem services (Johnston 1989). The University is also working with the City to involve local citizens in restoring bottomland hardwood forest within a recently acquired greenbelt. Twenty-five acres were planted by over sixty volunteers this past March, using bur oak, Shumard oak, and pecan.
Compiling City Green reports
City Green is a product of American Forests that calculates the dollar value of urban trees as an extension of the Arcview GIS program. Inventory was done on main city streets in association with the city's tree care inventory needs. This was supplemented with project-specific side street inventory. Dollar value is being calculated for urban trees before and after specific developments, and for proposed parcels to be purchased for open space. This information will support density trading proposed in association with a comprehensive plan, a method to cluster housing while protecting bottomland forest and upland forest greater than 10 acres or 15% or greater upland tree canopy cover.
Representative individual parcels will be evaluated with City Green and results extrapolated to estimate the total value of urban trees in the city comprehensive plan area.
Existing tree cover in other cities produces significant dollar benefits through ecosystem services such as: air quality ($15 million annually in Atlanta, $31 million annually in Austin); and stormwater control ($883 million in Atlanta and $1,423 million in Austin, during the effective life of a stormwater control structure) (American Forests 1997).
Publicizing and incorporating philosophies of Ian McHarg
The project team consists of: William Forbes and Dwight Barry, doctoral students, Environmental Science; Baird Callicott, Professor, Environmental Philosophy; Ken Dickson, Director, Institute of Applied Science. McHarg's Design with Nature was an early-career inspiration for two project team members, Professors Callicott and Dickson (McHarg 1969). The University has the leading environmental philosophy program in the nation and publishes the journal Environmental Ethics.
A recent issue contained an article promoting the idea that McHarg replace Aldo Leopold as the conceptual leader in environmental ethics, now that most of our population is urban (Gunn 1998). While Leopold continues to be a main source of environmental philosophy at the University, McHarg's emphasis on integrating humans with nature in urban and suburban settings is both studied and applied through community outreach, class discussions and readings, and application of geographic information systems to assist local environmental planners.
Literature Cited:
American Forests. 1997. The State of the Urban Forest: Assessing Tree Cover and Developing Goals. Washington, D.C.: American Forests.
Canter. L.W. 1995. Environmental Impact Assessment, 2nd ed. New York: McGraw Hill.
Costanza, R. 1998. The Value of the World's Ecosystem Services and Natural Capital Ecological Economics 25, 3-15.
Gunn, A. S. 1998. Rethinking Communities: Environmental Ethics in an Urbanized World. Environmental Ethics, Vol. 20. No. 4, 341-360.
Johnston, J. 1989. Urban Development and Fish and Wildlife Habitat of the Dallas/Fort Worth Metroplex. Washington, D.C.: USDI Fish and Wildlife Service.
McHarg, I.L.1969. Design with Nature. Garden City, N.Y.: Doubleday Press.
Morgan, D. J. Tolisano. 1998. An Ecological Assessment of Open Space in Santa Fe and the Extraterritorial Zone. Santa Fe, N.M.: City of Santa Fe.
Murray, R., K. Williams, S. Harris. 1991. Economic Impacts of Protecting
Rivers, Trails, and Greenway Corridors. Washington, D.C.: National.
Copyright 2000 By Authors
William Forbes
Dwight Q. Barry
J. Baird Callicott,
Kenneth L. Dickson,
Institute of Applied Sciences
University of North Texas
P.O. Box 310559,
Denton, TX 76203
(940) 565-2374
wf001@students.cas.unt.edu