Nitrogen runoff from forestland Grant: A University of Maryland lab has won $700,000 in federal funds to study the link among woodlands in the bay watershed, gypsy moths and Chesapeake pollution.

On the Bay

October 31, 1997|By Tom Horton | Tom Horton,SUN STAFF

IS THE HEALTH of trees on Appalachian slopes connected to the health of oysters and fish in the Chesapeake Bay?

In general, the answer is simple.

It is well-documented that rain falling in the bay's watershed carries far less pollution from forestland (about 60 percent of the watershed) than from farms, cities, golf courses and other land uses.

In restraining major pollutants such as nitrogen and phosphorus, our 25 million acres of forest are doing at least as much work as all our sewage-treatment plants and industrial discharge controls, and at considerably less cost.

But the forests' year-to-year impact may be far more variable than assumed, scientists at the University of Maryland's Appalachian Environmental Laboratory in Frostburg now think.

Their suspicions, which they recently got a $700,000 federal grant to pursue, began to form a decade ago.

Keith Eshleman, an environmental scientist at the Appalachian lab, was investigating the impact of acid rain on trout streams in Virginia's Shenandoah National Forest.

That was about the time that the gypsy moth had begun to move south in large numbers across the Mason-Dixon Line and down the spine of the Appalachians.

The insect, which was unknown in the bay watershed before 1965, by 1990 had infested virtually the whole of its forests.

The scientists studying streams in the Shenandoah noticed a curious thing that had nothing to do with acid rain.

Huge amounts of excess nitrogen were moving out of the forests, down the waterways -- up to 50 times normal.

These releases of one of the key nutrients that are overfertilizing the bay and robbing oxygen from aquatic life appeared to follow defoliation of forests by the leaf-munching moths.

At the peak of gypsy moth devastation in 1990, Eshleman says, close to 12 percent of the watershed's forests -- more than 2.5 million acres -- was defoliated.

If one extrapolates to the whole watershed from the few small streams studied to date, the moths' banqueting has major implications for the bay.

Currently, scientists assume forests each year deliver to the bay few pounds of nitrogen per acre in runoff. But in a year like 1990, this might actually increase by tens of millions of pounds.

This is enough, Eshleman says, to have a significant impact on the overall scheme of bay water quality. Total nitrogen entering the bay from all sources, for example, is estimated at about 230 million pounds a year.

Factoring in the "real" forest impact may affect the computer model used by governments in the region to calculate how fast they are reducing nitrogen to restore the bay's health.

It might place a higher premium on controlling gypsy moths, which are already the target of extensive spraying.

The moths since 1991 have entered a down cycle in the bay region, and currently cause little new defoliation; but it is anyone's guess when they will come back, or how strongly.

In fact, gypsy moth defoliation is only one of many changes that are taking place in the watershed's forests, Eshleman says.

The very quality of Appalachian forests is undergoing substantial change, as modern fire suppression, along with gypsy moth attacks, favors survival of maples over oaks, for example.

Commercial forestry practices are another agent of change. Pennsylvania, for example, is preparing a wide-scale increase in harvesting its maturing hardwood tracts.

The out-of-control populations of whitetail deer, browsing forest understories literally out of existence, are another.

The broader aim of his lab's research will be to devise ways to assess water quality impacts of these and other variables in the forest that most of us, including the people behind the most sophisticated bay computer models, treat mostly as an unchanging landscape.

"What we're after is linking large landscapes with water quality," Eshleman says.

Indeed, the $698,000 grant awarded by the U.S. Environmental Protection Agency highlights the quiet but dramatic change occurring at a laboratory long overshadowed by the university's two other bay research centers, at Solomons on the Patuxent River and at Horn Point on the Choptank.

When I began covering the environment in the 1970s, I associated the Appalachian lab more with cottontail rabbit research than with anything related to the bay and its watershed.

In fairness, it had come well beyond that by the 1980s but was still a part of the laboratory system that didn't fit in.

A new master plan for the lab, now in its fourth year, set out to make the university a leader in studying the extraordinarily complicated interactions of the bay and the landscapes it drains.

As anyone who follows the extensive effort to restore the Chesapeake to health can see, this so-called landscape ecology is where the action is headed.

Traditional sources of pollution, the sewage pipes and industrial outfalls, are well-understood and highly regulated now.

What washes off and leaks from the land, from chicken manure and septic tanks to the discharges from moth-eaten oaks and timber clear-cuts, is the unfinished agenda.

Pub Date: 10/31/97

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