A national committee led by Robert W. Howarth, Cornell's Atkinson Professor in Ecology and Environmental Biology, warns that excess nitrogen from the land and atmosphere is threatening the biodiversity of coastal ecosystems
The committee, which was organized by the National Research Council, issued its report earlier this week and called for the federal government to work with state and local agencies to develop a comprehensive national strategy to combat both nitrogen and phosphorus pollution in coastal waters. The study headed by Howarth, a biogeochemist, was funded by the National Oceanic and Atmospheric Administration, the Environmental Protection Agency, the U.S. Geological Survey and the Electric Power Research Institute. The National Research Council is the principal operating agency of the National Academy of Sciences and the National Academy of Engineering.
"Excess nutrients, especially nitrogen, in our coastal waterways, start a dangerous chain of ecological events that are exacerbating harmful algal blooms such as 'red tides,' contaminating shellfish, killing coastal wildlife, causing seagrass dieback, reducing biotic diversity and contributing to a host of other environmental problems," Howarth said, commenting on the panel's findings.
He said excess nutrients make their way to the coast by way of both the atmosphere, from the burning of fossil fuels, and in rivers that get polluted by agricultural runoff and wastewater treatment plants. The report stated that all of the nation's coasts are affected and said conditions in many coastal areas will grow worse unless immediate action is taken to reduce nutrient pollution.
Coastal environmental quality could be significantly improved if local and state efforts focused on reducing nitrogen and phosphorus releases, the committee said. However, local and state oversight often is not sufficient for protecting large watersheds that span several states or for dealing with pollution sources that are distant from coastal areas, the committee said, pointing to long-distance transport both in rivers and in the atmosphere.
The study assessed 139 coastal areas and identified 44 as "severely affected" by high levels of nitrogen and phosphorus. Problems are said to be particularly severe along the Mid-Atlantic coast and the Gulf of Mexico, where a "dead zone" forms along the Louisiana and Texas coasts each spring.
Nitrogen and phosphorus are naturally occurring nutrients that are critical to support plant life in marine ecosystems. But too much of either nutrient, especially nitrogen in seawater, causes an overabundance of phytoplankton and other organisms, which in turn use up available oxygen and destroy or drive away other marine life. These blooms and the excess nutrients that cause them have been linked to the decline of some fisheries, manatee deaths on the Florida coast and the loss of coral reefs and other important marine habitats.
Human activities have more than doubled the amount of nitrogen in the environment globally from 1960 to 1990, the report says, with the use of synthetic fertilizers accounting for more than half of that growth. In the United States, an estimated 20 percent of nitrogen in fertilizers seeps into groundwater, rivers and streams, gradually making its way into coastal waters.
Other sources include animal wastes and wastewater treatment plants. In addition, combustion of fossil fuels releases nitrogen compounds to the atmosphere, where they fall to Earth in acid rain and add large amounts of nitrogen to some coastal waters, according to the report. The report, titled "Clean Coastal Waters: Reducing the Effects of Nutrient Pollution," is available at the web site http://national-academies.org.
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