A recipe for sustainability.

What is the state of our urban forests? It's a question we've been asked - and we've asked ourselves - a lot lately That's partly because we're headed south to Atlanta for the 8th National Urban Forest Conference, a biennial gathering of people who care about the environment in our cities and towns, especially the trees and forests that help make them livable.

Throughout this century AMERICAN FORESTS has promoted the benefits of city trees and what we as individuals and a society can do to spread those benefits. Often communities have tried to reduce the formula for success to basic principles. But as times change, the ingredients in the formula for success also change, and that means benefits have to stretch farther.

For a couple of decades now, people have looked to AMERICAN FORESTS for the numbers on city trees: how many are there, their condition, are more being planted than are dying?

Six years ago we surveyed 20 cities and found most of their urban forests to be lacking - lacking in trees and tree care, lacking in money and personnel, lacking in stature.

A lot has changed since then, and not just in cities themselves. The technology to map and quantify urban forests is nothing short. of staggering. No longer is our primary concern with a community's street trees. As important as they are, the trees along streets and roads are only 10 percent of the trees in our communities. Today we have the ability to include the other 90 percent in our assessments.

That's important because it allows communities to integrate natural resources in the planning process. We can detail the value of trees in specific neighborhoods by gathering satellite images, aerial maps, and selected ground surveys and running that information through desktop computers programmed with the latest research on the relationship among trees, water, and air pollution. Using software we've developed, we can calculate how much a city could save on certain expenses by increasing tree cover - or by retaining what's there.

With this technology in hand we set out earlier this year to look again at our nation's urban forests. Remember, 80 percent of the U.S. population lives in or around urban areas. With so many of us living in cities these days, conditions must have improved. Right?

Not necessarily.

While some cities have upped their level of concern for the community's trees, they still do not understand their costs and benefits. Community leaders need to know what trees do, how they do it, and how best to take advantage of it.

We even found a federal agency - FEMA, the Federal Emergency Management Agency - that, as reported on page 11, has stopped paying to replace public trees and shrubs lost in disasters. In response we have just two words: Hurricane Andrew. We wish FEMA officials would talk with anyone who has struggled beneath Florida's baking sun to restore what was lost on that August day five years ago.

A less urgent but still compelling example is from our conference host city. Atlanta ranked dead last in our 1991 survey. And while we haven't ranked cities this time around, we suspect Atlanta would fare better. Its downtown is looking greener these days - 12,000 large shade trees greener, to be precise - thanks to a massive pre-Olympic tree planting campaign, much of it spearheaded by Trees Atlanta. So is Atlanta all it could be? No.

We have just calculated that trees in the region have been providing stormwater services equivalent to a $2 billion reservoir system. And this wasn't all of the trees in Atlanta, just those lost to development over a recent seven-year period.

There is no simple "recipe" for building a sustainable city; the problems and challenges are too complex. One ingredient that is gaining in importance, however, is healthy trees - healthy urban forests.

We offer this issue of the magazine as a cookbook of recipe suggestions: examples of cities and community groups that are working toward a goal of sustainability, the principles many are using to help set their course, and a number of the pieces necessary for guiding healthy cities - from greenways to clean air. As a sample of our wares, the center spread this time features city trees we at AMERICAN FORESTS and many of our partners have planted.

Overall, I'd call it a recipe for success.