Scientists spotlight nutrient pollution

Nitrogen, phosphorus imperil coastal waters

April 05, 2000|By Heather Dewar and Tom Horton | Heather Dewar and Tom Horton,SUN STAFF

A National Academy of Sciences report identifies nitrogen pollution, the environmental problem that Chesapeake Bay managers have been trying to control for more than a decade, as the most serious threat to coastal waters nationwide.

The report by a dozen top marine scientists, made public yesterday, calls for a national strategy to reduce the flow of nitrogen and phosphorus into rivers, streams and bays. The overabundance of these two key nutrients is causing serious environmental damage all along the nation's coast, the report said. Excess nitrogen, which comes from agricultural runoff, smokestack pollution, human sewage and animal waste, is a particular threat, the report concludes.

Since 1997, when an outbreak of toxic Pfiesteria piscicida on Maryland's Lower Eastern Shore was linked to nutrient pollution, scientists and government policy makers have been paying more attention to the problem. The National Academy of Science report takes the focus a step further, said Cornell University ecologist Robert W. Howarth, chairman of the panel that wrote the report.

The scientists stated "that nutrients are the biggest pollution problem of coastal waters in the U.S., and that nitrogen is clearly the problem in most places," Howarth said.

Nitrogen is Earth's main fertilizer, and for millions of years it has been in short supply in nature. Plants on land, in rivers and in seas evolved to make efficient use of the limited amount available.

But the modern era's two great technological leaps forward, the Industrial Revolution and the Green Revolution, have vastly increased the amount of nitrogen flowing through environments around the world.

Human activities, from the use of chemical fertilizers to the burning of nitrogen-rich fossil fuels in smokestacks and car engines, more than doubled the amount of nitrogen in circulation in the environment between 1960 and 1990, the National Academy of Sciences report says.

The result is runaway growth of algae, which clouds coastal waters, damages sea grasses and coral reefs, and triggers declining seafood harvests. The nutrients are also suspected of triggering a boom in outbreaks of toxic algae, which in recent years have killed manatees and porpoises in the Gulf of Mexico and have made people sick in Southwest Florida, in coastal North Carolina, and along some rivers of Maryland's Lower Eastern Shore.

The problem is worst in the Mid-Atlantic region and the Gulf of Mexico, the report says, but it's all-pervasive. The National Oceanographic and Atmospheric Administration studied 139 coastal areas from Washington State to Maine, and found 44 of them were "severely affected" by nitrogen and phosphorus pollution.

Among them is the Chesapeake Bay, where state and federal environmental managers have been trying since 1987 to reduce nutrient pollution, considered a key step toward restoring the region's once-abundant marine life. The Environmental Protection Agency's Chesapeake Bay Program's long-standing goal called for nitrogen flows into the bay to be reduced by 40 percent -- a goal that in the mid-1980s seemed a good guess about what kinds of reductions could be achieved, although the goal still hasn't been met.

The National Academy of Sciences report calls for similar nitrogen reduction goals to be set for all the nation's coastal waters. But rather than "arbitrary" targets like the Chesapeake Bay Program's, the limits should be based on detailed studies that show the maximum amount each area can handle without environmental harm.

That will be hard to figure out, even in the best-studied areas like Chesapeake Bay, said Chesapeake Bay Program senior scientist Kent Mountford.

"I'm not sure we know how to do it," said Mountford. Bay scientists know that the Chesapeake Bay is getting about seven times as much nitrogen as it did before Europeans settled here. But they know very little about the effects of lower levels of nitrogen on the bay's aquatic life, Mountford said.

The federal government is already paying for long-term studies of environmental problems at seven different sites along the coast, including one in Baltimore. The National Academy's experts recommend that those research programs should expand studies on nitrogen and phosphorus pollution to help scientists learn how much nutrient pollution is too much.

The report also singles out Maryland's 1998 Water Quality Improvement Act, which requires virtually all Maryland farmers to come up with plans for controlling the runoff of nitrogen and phosphorus from their land by the year 2002. The academy said similar nationwide controls on farm runoff are needed, whether in the form of a federal law similar to Maryland's, as subsidies and incentives to farmers, or as pollution taxes.

The report said urban and suburban areas' contributions to nutrient pollution need to be better understood. Since the Northeast and some other parts of the country get most of their nitrogen overdose from air pollution, federal laws need to be revised to include controls on airborne nitrogen, the report said.

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