"One of our big concerns now is that we know the world's soils have at least three times more carbon than plants, and that increasing the nitrogen hitting these soils could change the size of that huge pool," he said. Since the pool is so large, even a small change could have a big effect on the atmosphere, and therefore future climate."

Scientists have documented increases in how much C02 is being produced by human activity, and concluded that only about half of that amount is reaching the atmosphere, said Townsend. So the carbon sinks on Earth taking up and storing the carbon molecules in the world's vegetation, soils and oceans must be immense, he said.

"If these sinks slow down or turn off in the near future, we could see much larger increases in atmospheric C02," said Townsend. "If cold tundra soils are sensitive to nitrogen, it raises concerns about what might be happening in other, warmer parts of the world where things can change more rapidly," he said.

"Niwot Ridge is by no means unique," said Townsend. "Nitrogen deposition is going up all over the world, especially throughout the United States, Europe and much of Asia." In the eastern United States, for example, scientists are seeing as much as 10 times more nitrogen flowing into the rivers compared to just a few decades ago.

"I think the problems we are seeing from the altered nitrogen cycle are worse than what we are seeing in climate change around the world, at least for now," he said. "In the history of the Earth, half the nitrogen fertilizer ever used has been applied since 1990. A lot of this nitrogen does not go where it is supposed to, causing a cascade of environmental problems that are worsening at an alarming rate."

Although rivers like the Mississippi have many times the amount of nitrogen than
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Contact: Alan Townsend
alan.townsend@colorado.edu
303-492-6865
University of Colorado at Boulder
30-Oct-2002