A NASA-funded study of ancient and unpolluted South American forests promises to upend longstanding beliefs about ecosystems and the effects of pollution in the Northern Hemisphere.

The study, published in the Jan. 24 issue of Nature, focused on nitrogen, a plant nutrient that plays a critical role in maintaining everything from the health of local waterways to the global climate.

The study finds high levels of inorganic nitrogen in the United States, long thought to be the natural mainstay of the ecosystem, are really the result of acid rain and agricultural fertilizers. The authors argue that the ecosystems of South America, with their preponderance of organic nitrogen, are a window into the past, showing that U.S. ecosystems were very different before the industrial revolution.

Ecologists previously thought that nitrogen-containing minerals, referred to collectively as inorganic nitrogen, have always been the dominant nutrient in forests worldwide. The study of South American forests, however, showed a sharply different picture: complex, organic compounds are the main form of nitrogen in unpolluted ecosystems.

"We traveled in time by traveling to South America," said Lars Hedin, a co-author of the study and a professor of ecology and evolutionary biology at Princeton University.

The information they uncovered could have far-reaching impacts in many areas of ecology, from predicting the pace of global climate change to understanding the consequences of acid rain and agricultural run-off.

"Nitrogen is a sort of master variable," said Steve Perakis, the paper's lead author and a research scientist with the U.S. Geological Survey. "If we don't get the fundamental elements of the nitrogen cycle right, we can't answer many other ecological questions."

The findings raise questions about our understanding of global warming, which is partly caused by fossil fuel burning and increasing levels of heat-trappin
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Contact: Cynthia O'Carroll
cocarrol@pop100.gsfc.nasa.gov
301-614-5563
NASA/Goddard Space Flight Center
24-Jan-2002