Biogeochemistry -- A window into the Earth's ecologi...( Humans are fundamentally altering th...)

Humans are fundamentally altering the Earths chemistry. Many of societys most pressing environmental problems, from climate change to acid rain, stem from human activities that disrupt natural chemical cycles. Moving toward a sustainable future will depend on identifying and reversing actions that have such a huge impact on the Earths chemistry.

So concludes the president of the Institute of Ecosystem Studies, Dr. William H. Schlesinger, who has been investigating environmental chemistry for over two decades. On October 29th, Schlesinger will present his latest analysis of human impacts on the global nitrogen cycle as the Michel T. Halbouty Distinguished Lecturer at the Geological Society of Americas annual meeting in Denver.

Humans, Homo sapiens, are now the dominant species changing the Earths surface chemistryits biogeochemistry. How our changes affect the fundamental life-support processes of the planetincluding the water cycle, photosynthesis, agriculture, and fisheries will determine the future quality of life on Earth. We must ask how much global change we can tolerate and assess how fast nature can adjust, commented Schlesinger.

His presentation will outline human impacts to nitrogen, sulfur, and carbon cycles as well as connections among the three. While some fluctuations in the Earths chemistry are natural, Schlesinger notes that, Current human impacts have caused changes that are unprecedented in the history of organized human society.

Some of the most dramatic changes have occurred in the sulfur cycle, which has increased by 30% as a result of coal burning and internal combustion engines. Excess sulfur can cause toxicity in plants and, when oxidized in the atmosphere, is a principal component of acid rain.

Human impacts to the nitrogen cycle have also been substantial, largely due to the application of agricultural fertilizers. In an interesting twist, by stimulating crops to maximize yield, humans h
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