IN RESTORING environmental quality, there's an understandable tendency to focus on reducing pollutants that directly degrade water and air quality.
Equally important, however, is improving what one might call environmental "resilience" -- the systems that help nature help itself to reduce pollution.
With oysters, dredging long ago leveled the reef structures in which shellfish grew best. Draining wetlands removed an important filtering system. The vast meadows of submerged grasses driven from the bay by pollution absorbed huge quantities of pollutants.
Largest among the Chesapeake's systems of natural resilience is the forest that originally covered about 95 percent of its 41-million-acre drainage basin, or watershed. Forests now cover less than 60 percent.
You can argue that forests have increased in many areas from the peaks of clearing for tobacco in Colonial times or clear-cutting for timber around the turn of this century.
But when forests fall nowadays, it's often to development. Trees can regrow from farming and logging, but roads and houses, malls and parking lots foreclose that option.
Also, all the modern pollutants in the air and land runoff make the remaining forests' natural capacity to absorb and filter contaminants more critical than in previous eras.
So it is welcome, albeit sobering, to see the unveiling this week of a major new tool for understanding and reversing forest declines throughout the bay's watershed.
The nonprofit conservation organization American Forests, with the help of the U.S. Forest Service, analyzed satellite images of bay forests over a period of 24 years -- 1973, 1985 and 1997.
They examined a 1.5-million-acre region around the Baltimore-Washington metro corridor and 11.5 million acres of the Chesapeake Bay watershed, extending west from Delaware to around Hagerstown and south from the Pennsylvania border to Norfolk, Va. -- including the bay and its tidal rivers.
No surprise, in the metro corridor forests took a heavy hit in the 24-year period -- from 821,000 acres to 555,000, from 55 percent of the land to 37 percent. Developed land rose from 462,000 acres to 732,000, from 31 percent to 49 percent.
In 1985, the two trends intersected, with development replacing trees as the dominant feature of the landscape.
(Percentages don't equal 100 percent. About 14 percent of the landscape falls between American Forests' definition of "forest" -- more than half canopied by trees -- and "developed" -- less than 20 percent tree canopy. This is mostly parks, open space and lightly developed residential.)
Surprising were the changes analyzed for the larger region, which includes a quarter of the entire, six-state bay watershed and lots of rural landscape.
It showed just as much forest loss as the metro corridor. The larger region lost nearly 2 million acres of forest -- the equivalent of clearing a Baltimore County-sized forest every five years.
This was a testament to unplanned, sprawl development, said an American Forests spokesman, and also to agricultural clearing, particularly along bay streams.
Sobering trends. But the main purpose of the analysis "is to show how you can do a better job of incorporating trees in the development process -- and save a lot of money in the process," he said.
To that end, American Forests, which is doing similar analyses around the country, will provide satellite data and its CITYgreen software, at cost, to local governments or citizens groups.
This allows analysis -- down to the level of a city block or less -- of forest status and trends. It also allows running scenarios to determine the best strategies for restoring trees and forests.
It's not free, but costs are reasonable. The software's about $700, and the satellite data for a whole county might run $2,000. Scanning aerial photos into the software is necessary to get finer resolution for urban areas. But that cost $7,000 for the city of Cincinnati, which is using it for forest planning.
That's piddling compared with the value of restoring trees, something well documented in the American Forests analysis. Some examples:
The 24-year forest loss in the Baltimore-Washington corridor represents a billion dollars worth of engineered storm-water controls to replace the trees' natural functioning and $24 million each year to make up, with technology, for trees' air pollutant removal.
Increasing forest cover in the Baltimore area to a recommended 40 percent (from 31 percent) would save $102 million in storm-water controls and $3 million a year in air-quality control.
American Forests has committed to planting a million trees in the bay watershed in the next year. "A drop in the bucket, but a good start," they say.
To help, call 1-800-545-TREE. Ten dollars pays to plant 10 trees. For information about CITYgreen software and forest data, call 202-955-4500, Ext. 227.
About 20 years ago I reported on Gary Moll, the American Forests vice president and the brains behind its forest project. He was a Maryland forester then.
Guess what he was doing? Trying to convince developers that they could build without destroying so many trees.
Pub Date: 3/19/99
