Digging out of a tree deficit: Changing a city from gray back to green requires computer savvy, high-tech pictures, and local action.

When Sheila Hogan wants to tell the story of the decline of trees in Washington, DC, she stops talking and starts showing old black and white photos. The glossies, taken in the 1930s, 40s, and 50s, show the city's main arteries like K Street and East Capitol Street lined with statuesque American elms; their vase-shaped, expansive canopies shading the streets.

Hogan, executive director of the Casey Trees Endowment Fund, doesn't need recent photos to illustrate the contrast today. Local residents and politicians know the images in those old photos are a far cry from the picture along those same city streets today, where 10-foot Japanese zelkovas and Shademaster honeylocust struggle for survival in planter boxes imbedded in brick sidewalks. Along some streets, there are no trees at all.

Photos can help make some people pay attention to a city's "tree deficit"; they can even inspire activism. But they don't do much for municipal planners who need more than nostalgia to prepare for the future.

While more and more policymakers and planners have come to understand the environmental and economic benefits trees provide in terms of stormwater management, air quality, and energy conservation--and as state and federal regulators develop tougher standards in all these areas--what planners need now are tools to map out the urban forest and to incorporate that "green infrastructure" into their thinking.

After all, it's easy for planners to figure out where sewer lines are laid, power lines are run, and manholes placed: The planners just check out a computer database that maps the location of those various components through technology called Geographic Information Systems (GIS). What's hard is figuring out where the trees are planted.

And that's where AMERICAN FORESTS believes it can help cities. With support from the U.S. Forest Service and the use of new high-resolution satellite imagery, AMERICAN FORESTS is working on high-tech mapping of individual trees. Its first project, which will he presented at the 2001 National Urban Forest Conference September 5-8, focuses on the Washington metropolitan region with the idea that it could serve as a model for cities and regions around the country.

An earlier study that detailed the District's declining tree cover helped prompt Betty Brown Casey's $50 million endowment to reforest the city. The Casey Trees Endowment Fund is helping to fund the current DC analysis.

For years, AMERICAN FORESTS has used other technology, like images from the Landsat 7, to show policymakers the alarming rate at which green spaces were being overtaken by gray surfaces. The images, taken several years apart, made the point that the trend toward declining tree canopy coverage was costly--not just for environmental reasons but for economic ones: the more impervious surfaces, the more stormwater runoff, and the more need for building expensive infrastructures to manage stormwater.

But the Landsat only gave a 30-meter pixel resolution, too broad to discern anything smaller than a Wal-Mart or a cluster of at least six mature trees.

"It's a challenge for us to take Landsat and talk about managing" the urban forest, explains Phillip Rodbell, program leader for the Forest Service's Northeastern Area Urban and Community Forestry Program. He was intrigued by AMERICAN FORESTS' plan to use new, higher-resolution images.

"It's very important to the Forest Service that the value of the urban forest resource is easily comprehended by our champions in Congress." And from a local policy perspective, "It's important that we graphically illustrate the scope and value of the urban forest resources.

"What I really like about AMERICAN FORESTS' model," Rodbell adds, "is its ability to capture people's imaginations and drive further investment in trees and forests as contributors to quality of life."

To understand the model AMERICAN FORESTS has in mind, it helps to know a little something about GIS. Basically, GIS lets you take data that would normally appear on a spreadsheet and apply them spatially. GIS "marries data with maps, explains Michael Sherman, director of the office of technology for the National Capital Planning Commission, a federal agency working with AMERICAN FORESTS on the project.

GIS displays different information in different layers, letting you add or subtract details from the map. It's sort of like laying different transparencies on top of each other--say, one layer for road lines, another for building lines, and another for residential lot lines.

One expert likened it to building a hoagie: Every layer you add makes the sandwich that much more flavorful.

Being able to readily call up digital maps that contain different levels of complexity helps planners like Sherman make decisions about how to use different parcels of land in the future.

For most city planners, the considerations are common: how and whether to widen roads and design new subdivisions, for instance. And if planners and policymakers are trying to take trees into consideration, and if they are trying to adhere to the level of canopy coverage prescribed by AMERICAN FORESTS--the recommended amount is generally an average of 40 percent citywide--they've got to know where the trees are.

Washington, DC, has GIS mapping, says Sherman, but "No one in the District yet has a very good tree or vegetation layer." Even so, he already has grand plans for what the city and the federal government could do with that information.

"I can see a whole range of layers: from soil conditions to tree-planting boxes, to maintenance conditions, to what species are planted where and when and who's responsible for maintaining them."

He adds: "Down the road I could imagine that when we're reviewing a potential project, we could say, Hey, you guys are going to tear down 10 elm trees or 10 cherry trees' and we'd instantly know the number of trees and when they were planted and the potential environmental impact."

To create the kinds of layers that Sherman envisions, AMERICAN FORESTS first must analyze the high-resolution images, which have been taken by satellite.

What makes the new satellite images so unique is the high-resolution "pictures" they collect. The black-and-whites, or panchromatics, are at 1-meter resolution; the color, or multispectral, at 4-meter resolution.

That means the satellite can distinguish objects on the Earth's surface as small as 1 meter square, or about 3 feet. As such, the "camera" can detect individual trees, which, in turn, means that analysts can also calculate exactly the benefits those trees provide in dollar terms. In the past, less precise imagining forced AMERICAN FORESTS to merely extrapolate those numbers.

Of course, figuring out what's in those high-resolution images isn't as simple as looking at a photograph. It requires analysis. That's because the color is really just a reflection of light. Different materials reflect light differently; the onus then is on the GIS specialist to distinguish trees from grass, for example. AMERICAN FORESTS bought and is now analyzing 634 square miles of images of the Washington, DC, area. The organization is starting its analysis with a few specific locations, like an area along the city's Woodley Park, which will be presented at the September conference. The site was chosen for a couple of reasons--the GIS mapping of that area is especially full and the politics around improving living conditions in that area are particularly ripe.

Technology has proved to be a powerful tool for showing politicians and corporate powers why the forest is essential for urban areas. Using Landsat images, aerial photography, and its own CITYgreen software, AMERICAN FORESTS has conducted nearly a dozen Regional Ecosystem Analyses since 1996. Each one--from Canton, Ohio's to Colorado's Front Range--has attracted attention from politicians and the press. And that has led to a big payoff for urban forests.

A new analysis is underway now in the Willamette and Columbia River valleys of Oregon and Washington state. Salem is among the nine communities participating in the study. The city already has a tree-preservation ordinance but was looking for a more comprehensive plan for preserving trees and restoring the tree canopy in the city, says Peter Gutowsky, a natural resources planner for the city who has been helping with the on-the-ground tree inventory.

But before the city could come up with a comprehensive plan, it needed accurate information about its current tree canopy. Salem hired AMERICAN FORESTS to analyze 10 sample sites around the city to document how the canopy had changed in those areas over time and how much it would need to increase to derive higher economic benefits.

"Once we have the results of this study," says Gutowsky, "we're going to create a citizens advisory committee, a representative group of stakeholders to evaluate the results and consider expanding our regulatory approaches to protect trees in our community."

He adds: "What this information will do is educate residents and elected officials and city staffs about the importance that forest canopy provides to a metro area. I think each community is then left with a very daunting task of determining the best methods for protecting their forested areas."

In Cincinnati, after using CITYgreen to analyze the canopy there, the city's park board decided that one way to protect trees and reforest the city was to turn to a business in the community: the utility company, Cinergy Corporation. The company now is providing the Cincinnati Park Board with $40,000 for tree-planting projects to help the city meet its goals for canopy coverage.

David Gamstetter, natural resource manager for the park board, says the energy company is concerned about the environment. It has to be: Like all utility companies, Cinergy is under pressure from the U.S. Environmental Protection Agency to meet tougher pollution standards.

Even so, Gamstetter says, "We wouldn't have gotten the money from Cinergy" without the CITYgreen analysis. He explains. "You can talk about how good trees are, but until you can start to quantify the benefits and talk real numbers," you're not going to get anywhere with most companies.

"The software allows us to make the trees grow digitally," he adds, "so we were able to show what we were going to accomplish through the tree forestation and how much that would change a community and what the other benefits would be."

Ray Bengel, an official with Cinergy explains that the company constantly has to prune or cut down trees to put up and protect its power lines. So the tree-planting program appealed to officials who "wanted to give back to the community." Moreover, he notes, the company can get "carbon credits" from the federal government for planting trees.

Betty Brown Casey also wanted to give back to the community when she set up her $50 million endowment to reforest the District. When Mrs. Casey read about AMERICAN FORESTS' earlier analysis, she remembered how much her late husband Eugene had loved his hometown's trees and extensive canopy cover and decided to champion its regrowth through the fund.

Executive Director Hogan's assignment now is to get an accurate tree inventory. That in itself is a tough job considering the disparate groups that have collected data on the urban forest over the years. She is relying in large part on AMERICAN FORESTS' analysis, which the foundation is helping to support, then she'll send out troops of volunteers and horticulture students for an on-the-ground inventory to assess tree health, species, etc.

Hogan is eager to have the analysis so she can put "hard facts and figures in front of policymakers to show them what we're talking about," she says. "Instead of speaking in general terms, it's really useful to sit down with the office of planning and the mayor's office and say this is exactly what we're talking about, this is why you should put more resources into landscaping and parks and recreation."

There will always be a place in Hogan's speeches for those black and white glossies. But she'll also be talking about the latest technology to trumpet the benefits of trees.

Courtney Leatherman is associate editor of American Forests.