Bringing Coastal 'Dead Zones' Back to Life

Each spring, the area in the Gulf of Mexico just off the Louisiana and Texas coasts turns into a "dead zone." Excessive amounts of nitrogen and phosphorus--which make their way to the Gulf from the atmosphere and via rivers polluted with agricultural runoff and municipal and industrial waste--trigger algal blooms. The algae use up available oxygen, killing bottom-dwellers such as oysters, clams, and snails, and driving away fish, shrimp, and crabs. And it isn't just the Gulf area that is affec

Jun 26, 2000
Robert Howarth

Each spring, the area in the Gulf of Mexico just off the Louisiana and Texas coasts turns into a "dead zone." Excessive amounts of nitrogen and phosphorus--which make their way to the Gulf from the atmosphere and via rivers polluted with agricultural runoff and municipal and industrial waste--trigger algal blooms. The algae use up available oxygen, killing bottom-dwellers such as oysters, clams, and snails, and driving away fish, shrimp, and crabs.

And it isn't just the Gulf area that is affected by an overabundance of nitrogen and phosphorus. All of our coasts are being damaged. Of 139 U.S. coastal areas assessed recently, 44 were identified as severely affected by high levels of these nutrients. Excess nitrogen is particularly harmful for marine ecosystems and can be linked to everything from increased outbreaks of red tides to the deaths of marine mammals and the loss of biodiversity. What's more, many scientists predict that the problem will worsen in the coming decades unless action is taken now to reduce nutrient excesses in U.S. waters.

State and local governments often are responsible for identifying and dealing with nutrient pollution, and their efforts can significantly improve coastal environmental quality. But state and local agencies can't do it all, and they certainly can't do it alone. To truly protect our coasts, rivers, and lakes, our nation needs a comprehensive strategy to prevent excessive amounts of nitrogen and phosphorus from entering our waterways.

Nutrient pollution is a complex problem that is taking on ever-larger proportions. For example, human activities have more than doubled the amount of nitrogen globally from 1960 to 1990, with the use of synthetic fertilizers accounting for the majority of that growth. More than half of all synthetic fertilizers ever produced has been used in the past 15 years. In the United States, approximately 20 percent of the nitrogen in these fertilizers seeps into groundwater, rivers, and streams, gradually making its way into coastal waters. Other sources of nitrogen include animal wastes, wastewater treatment plants, and the combustion of fossil fuels. When these fuels burn, nitrogen compounds are released into the atmosphere, and then fall in acid rain, adding significant amounts of nitrogen to some coastal waters.

Nutrient pollution often crosses local and state boundaries, making it difficult for various government agencies to act cohesively. Rivers can carry pollution for long distances. One of the many sources of excess nitrogen in the Gulf, for instance, might be runoff from a farm in Iowa. And nitrogen from the atmosphere is a nationwide problem. Large watersheds that cut across several states need uniform protection.

Much needs to be done to help state and local authorities address this problem. The federal government should take the lead on issues that span multiple jurisdictions or threaten federally protected natural resources. The government also should continue to set clear guidelines for the maximum allowable amounts of nutrients that are released in waterways and address overlaps in existing and proposed federal legislation.

Developing accurate estimates of nutrients in waterways that lead to the coast is essential for forming effective strategies to curb excesses. Federal, state, and local agencies should form partnerships with academic and research institutions to create a national monitoring program. And every 10 years, a nationwide assessment should be conducted to determine the extent of nutrient problems and the effectiveness of efforts to combat them.

But just as important, the federal government should be more effective in providing data, information, and technical assistance to state and local coastal authorities. A national information clearinghouse that provides assistance on request, or a complete database on the Internet with links to information, could go a long way toward helping regional authorities make more informed decisions.

Putting these practices into place, along with strengthening state and local efforts, could realistically reduce the number of severely damaged coastal areas by at least 25 percent in the next 20 years and ensure that no other healthy coastal areas become affected. By developing a systematic, nationwide plan to attack nutrient pollution at its many sources, the government will make huge strides in protecting the many precious natural resources in and around our waterways. It's time to put an end to coastal "dead zones" and bring marine ecosystems back to life.

Robert W. Howarth, professor of ecology and environmental biology at Cornell University, Ithaca, N.Y., recently chaired a National Research Council Committee that wrote the report Clean Coastal Waters: Understanding and Reducing the Effects of Nutrient Pollution, www.nap.edu/books/0309069483/html.

See also "Coastal 'Dead Zones' Get Attention."