Nitrogen-tainted runoff and other pollution problems caused by farming could cause as much or more environmental damage as global warming, according to a scientific study published in the journal Science.
At the same time, 128 leading ecologists signed a letter sent to congressional leaders yesterday, urging them to begin a $2 billion effort to reduce the nitrogen pollution that is creating a "dead zone" the size of New Jersey in the midst of the Gulf of Mexico's prime shrimping grounds.
The authors of the article and the letter say they are part of a concerted effort to raise public awareness about the seriousness of nitrogen pollution - the leading cause of the Chesapeake Bay's degradation - and other environmental effects of agriculture.
The scientists had "a sense that humans were impacting the globe in a variety of ways that went well beyond climate change, and yet climate change was getting the vast majority of the scientific attention and the public attention," said ecologist David Tilman of the University of Minnesota, lead author of the article written by 10 U.S. and Canadian scientists and published yesterday.
After studying worldwide trends in land-clearing for farming, fertilizer use and pesticide use, "it became clear to us that the single major driver of global change, other than energy use, was coming from agriculture," Tilman said.
Over the next 50 years, an area larger than the United States will be converted from wild land to farmland and the use of nitrogen fertilizer and pesticides will increase nearly threefold, the scientists concluded.
As a result, they say, nitrogen pollution of lakes, rivers and bays - already the single greatest source of water pollution in the United States and the world - will increase to about 2 1/2 times present levels. Fish catches will fall, natural variety will decline and the land's ability to provide valuable services such as flood protection and pollution cleanup will fall sharply.
The scientists say their article is intended to show politicians, ordinary citizens and the agriculture industry that there will be grave environmental consequences unless the farming techniques of the Green Revolution, which relied in part on chemicals to increase food production, are replaced by less destructive methods.
"It's really more of a warning, we hope, than a prediction," Tilman said. "We'd be very disappointed if our prediction turned out to be true."
Nitrogen pollution is blamed for more than 40 "dead zones" worldwide, where nitrogen-fueled algae blooms consume the oxygen in the water, killing or driving away all living things. About one-third of Chesapeake Bay waters are lifeless in summer.
North America's largest dead zone is in the Gulf of Mexico, which receives runoff from about four-tenths of the continental United States. Last year, a study sponsored by the Environmental Protection Agency concluded the gulf's health would improve significantly if Midwest farms reduced fertilizer runoff by 30 percent.
An "action plan" endorsed by several Midwestern governors would give farmers incentives to reduce runoff from their land - by installing buffer strips of grass and trees to filter out pollution, restoring wetlands that act as natural filters, and reducing fertilizer use.
The proposal has won some support in Congress. Last week, a bipartisan group of Midwestern senators and representatives introduced legislation that would funnel $350 million in federal money to voluntary projects aimed at reducing runoff.
About $25 million would be used for urban streams, but most would be spent on reducing farm runoff, said Missouri Republican Sen. Christopher S. Bond, who introduced the Senate version.
In an interview yesterday, Bond said his proposal has the support of some farm groups and called it "an idea whose time has come." But the George W. Bush administration apparently doesn't agree. In its budget proposal, the administration eliminated funding for the existing Conservation Reserve Program, which pays farmers to take environmentally sensitive land out of production as a means to reduce pollution.
Bond said yesterday he is confident that Congress will fund the existing program. But persuading legislators to create a new anti-pollution effort will be much more difficult, he conceded.
It will take time to persuade Congress to act on nitrogen pollution, said ecologist Robert Howarth of Cornell University.
"I don't think it's high on their radar screen," said Howarth, the lead author of the scientists' letter asking congressional leaders to fund the gulf action plan. "I think Congress assumes it's going to be disruptive to the farm community. It doesn't have to be."
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