TEMPE, Ariz. Humans are having an effect on Earth's ecosystems but it's not just the depletion of resources and the warming of the planet we are causing. Now you can add an over-abundance of nitrogen as another "footprint" humans are leaving behind. The only question is how large of an impact will be felt.
In a Perspectives piece in the current issue of Science (Dec. 16, 2011), Arizona State University researcher James Elser outlines some recent findings on the increasing abundance of available nitrogen on Earth. In "A World Awash in Nitrogen," Elser, a limnologist, comments on a new study showing that disruption to Earth's nitrogen balance began at the dawn of the industrial era and was further amplified by the development of the Haber-Bosch process to produce nitrogen rich fertilizers.
Until that time nitrogen, an essential building block to life on Earth and a major but inert component of its atmosphere, had cycled at low but balanced levels over millennia. That balance ended around 1895.
"Humans have more than doubled the rate of nitrogen inputs into global ecosystems, relative to pre-industrial periods, and have changed the amounts of circulating phosphorus (like nitrogen, a key limiting ingredient for crops and other plants) by about 400 percent due to mining to produce fertilizers," Elser said.
The result has been immediate and widespread, he added.
Commenting on a major new finding in Science by G.W. Holtgrieve and colleagues, Elser said that signs of the "new N" appeared in all regions of the Northern Hemisphere in a remarkably coherent manner beginning around 1895, in concert with when fossil fuel combustion and large scale biomass burning accelerated across the globe. Another significant increase came around 1970 coincident with massive increases in industrial nitrogen fixation for fertilizer production, just as the "Green Revolution" got started.
The effects of the high nitrogen in
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Arizona State University