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

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.


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.


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.

The success of these three localities is worthy of praise and emulation but there is something even greater going on. Just like the old adage about the man who eats for a day when given a fish, but never goes hungry when taught to fish, cities are starting to think about and use their green infrastructure as natural capital. These are cities that are truly connected with nature.

If the urgency of reconnecting with nature was not apparent, it should be after the release this spring of the Millennium Ecosystem Assessment, a five-year study of the world's ecosystems conducted by 1,300 scientists from 95 countries. This extensive research effort showed human activity has degraded 60 percent of the world's ecosystems and, if existing trends continue, will cause some to collapse before the average sixth-grader retires in 2055.

The Millennium Assessment sheds new light on the economic and financial relevance of global ecosystems by presenting its findings in terms of ecosystem services: "Only by understanding the environment and how it works can we make the necessary decisions to protect it," the report says. "Only by valuing all our precious natural and human resources can we hope to build a sustainable future."


What is the process for turning city trees into dollar values on a balance sheet? The first step is establishing the structure of the land via high resolution imagery. That image is then classified into land cover types by a trained image analyst, and the work performed by the land determined using Geographic Information Systems (GIS) technology. Then scientific and engineering formulas are used to calculate the effect of the green infrastructure on stormwater management, water quality, and air pollution.

AMERICAN FORESTS believes that when green infrastructure benefits are quantified, the value of nature will become relevant to community leaders. Scientists call this documentation "quantifying the benefits"; voters call it accountability.

There is a large and measurable difference in the way a summer storm's rainwater flows from a parking lot and from a woodlot. Our cities tend to have a lot more parking lots than woodlots. Rainwater soaks back into the soil naturally in a woodlot but runs off a parking lot and must be captured in a storm sewer.

AMERICAN FORESTS has developed analytical tools that allow cities to compare the difference between using natural management and "concrete management" to deal with issues like stormwater runoff. It is possible for city officials to model different growth and development scenarios and evaluate the benefits of each--before they're constructed. Regardless of whether city leaders' emphasis is on money or the environment, the budgetary facts lead to the same conclusion: It pays to use green infrastructure.

Formulas used in AMERICAN FORESTS' analyses come from standard engineering formulas such as the Natural Resource Conservation Service's T-R55 model to calculate stormwater runoff and develop control measures needed for new developments.

Urban areas have become an important focus for AMERICAN FORESTS because it is where the majority of us live. Urban landscapes have grown dramatically over the last 50 years; as they grow, the landscapes--and the people who live there--have become increasingly separated from the natural systems they are built on. Landsat satellite images have documented this graying of our landscape, 20 percent more urban areas, 30 percent fewer natural areas since 1972.

But while many large urban areas have already lost a large portion of their natural capital, AMERICAN FORESTS estimates there is still about $400 billion worth of ecosystem services remaining in our urban forests. And while we have already lost billions in ecosystem services to existing development, some of these natural benefits can be recovered by greening the developed parts of a city. Smart development that incorporates natural systems is more cost-effective because it serves double duty: It provides both social and economic benefits for the community.

Sample Budget

Stormwater storage costs for 250-acre neighborhood

 Option 1 Option 2 Option 3
 % Landcover % Landcover % Landcover

Pavement/Structures 80% 60% 40%
Grass 15% 15% 15%
Tree Canopy 5% 25% 45%
Stormwater Storage Costs $4,700,850 $4,020,225 $3,276,075

RELATED ARTICLE: Reconnect with Nature and Save Tax Money

You can become an ambassador for green infrastructure in your community and help introduce natural systems and ecosystem services into your metropolitan area's growth and development process. Here's how:

1. Visit AMERICAN FORESTS' website ( for information on how to calculate the value of nature in your community.

2. AMERICAN FORESTS has entered into a partnership with one of the nation's most experienced image analysis companies, Sanborn Mapping Company, to help communities develop a green data layer. To do this, images need to be collected during the growing season when the leaves are on the trees. For details on developing a green infrastructure for your community go to

3. Use the free service available on the U.S. Geological Survey's National Map website ( to obtain an estimate of the value of your community's green infrastructure.

4. Present the analysis' findings to your elected officials. Show them it's possible to save tax money while improving air and water quality by using green infrastructure: trees and other natural elements of the landscape.

5. Help elected officials develop a green infrastructure approach for your community. Community leaders can develop a green data layer from high-resolution aerial or satellite imagery, classify the data into landcover classifications, and use AMERICAN FORESTS' CITYgreen software to calculate the value of the green infrastructure for various planning scenarios.

6. Once your community has adopted a green infrastructure approach, AMERICAN FORESTS can analyze the green data layer and provide your community with a detailed analysis of the entire city or particular areas of interest. Another option is for cities to purchase CITYgreen software, conduct a training session with AMERICAN FORESTS, and then carry out their own analyses. For more information on CITYgreen software and training, visit

Gary Moll is vice president of urban forestry for AMERICAN FORESTS.
COPYRIGHT 2005 American Forests
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2005, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

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Title Annotation:COMMUNITIES
Author:Moll, Gary
Publication:American Forests
Geographic Code:1USA
Date:Jun 22, 2005
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