Repairing ecosystems at home: three cities show why it makes financial sense to reconnect with nature in their own backyards

American Forests, Summer, 2005 by Gary Moll

What do Salem, Oregon; Roanoke, Virginia; and Charlotte, North Carolina, have in common? They are trendsetters, early adopters of technology to measure and use natural capital as a public asset. Natural capital is a physical asset, like the roads or buildings listed on a city's ledger. But unlike built structures, natural capital is trees, shrubs, and soil, which produce ecosystem services by moderating rainwater and cleaning water and air.

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Calling these natural functions "capital" is a change; traditionally only physical assets, those built by people, are on a city's budget sheet. Trees are the most prominent objects in a city's green infrastructure and the source of significant air and water benefits, yet traditionally considered a maintenance expense. Prosperous cities of the future will measure green infrastructure and calculate the ecosystem services it produces. Salem, Roanoke, and Charlotte have already started down that path.

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While it is true that no urban area has developed a solid bond with nature, some--like the three above--have made a connection. They realize that green infrastructure must be a part of the budget sheet if they are to balance their budgets in the future. To do that, they need to account for all the trees in their community, not just the ones along the street. Typically a city owns just 10 to 20 percent of the community's arboreal holdings; the rest are on private property. But the benefits they provide are available to all.

Most cities count street trees so they can do a better job of maintaining them. That's okay, but it still means trees are viewed as a budget expense. The challenge is in looking at them not as a budget expense, but as a budget benefit that helps produce cleaner air and water.

Consider what has happened in Salem, Oregon. High-resolution satellite images provide an accurate view of the city's land cover and therefore the documentation needed for accounting. The land planning department in Salem used the green data layer extracted from that imagery to calculate the effect of tree cover on stormwater runoff in the city's watersheds. Their findings demonstrated the value of trees in the watersheds and suggested that by planting more trees the city could realize 50 percent of the potential benefits in just 15 years.

Realizing the importance of public support, the planning department made the community a partner in the process by fully involving it in the process and encouraging public reaction. They created a website so residents could easily review the facts, then asked citizens to record their opinions with public officials via the website. The public's reaction? They urged public officials to make their watershed greener. New legislation soon followed.

Roanoke, Virginia, has also used high-resolution satellite imagery to connect with nature. For this rural city nestled in an Appalachian Mountain valley at the headwaters of three major rivers, the question was whether trees could reduce flooding.

Roanoke has suffered floods 18 times in the last 125 years, and the problem is worsening as building and pavement replace trees and other natural land cover. A group of civic-minded residents working with city officials on the problem decided to see whether increasing the city's tree cover might reduce the risk of flooding.

The benefit of tree-covered land for reducing stormwater is well documented, and the formula for calculating these benefits was part of an Urban Ecosystem Analysis conducted by AMERICAN FORESTS. Roanoke's civic-minded residents used the information gathered and their considerable personal skills in working with city management to develop a tree cover goal for the city. This goal calls for Roanoke to have tree cover over 40 percent of the city, a goal that will reduce the threat of flooding.

Mecklenburg County, North Carolina, encompasses the growing city of Charlotte as well as several smaller cities. It used high resolution imagery to document the county's green infrastructure in 2002, and the potential of this green asset is proving to be a good investment. A green infrastructure plan was developed at two scales--one using Landsat satellite images (taken from NASA satellites) to document landcover change over 17 years and another using high-resolution satellite and airborne imagery to make it possible to identify individual trees for daily decision making.

Local officials were shocked by the change in Mecklenburg County over those 17 years. Several urban areas more than doubled their amount of "gray" surfaces (buildings, sidewalks) while losing almost half of their tree cover and open space.

Local awareness soon became regional action, thanks to the influence of Mayor Patrick McCrory, the Charlotte Tree Commission, and the Centralina Council of Governments. The Landsat analysis was extended from one county to a 15-county region. The high-resolution imagery provided a detailed account of existing tree cover and, most importantly, data needed for daily decision making.