Biogeochemistry -- A window into the Earth's ecological health

Humans are fundamentally altering the Earth’s chemistry. Many of society’s 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 Earth’s 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 America’s annual meeting in Denver.

“Humans, Homo sapiens, are now the dominant species changing the Earth’s surface chemistry—its biogeochemistry. How our changes affect the fundamental life-support processes of the planet—including 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 Earth’s 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 have increased the uptake of carbon dioxide from the atmosphere, where it might otherwise contribute to global climate change. This is because plants remove carbon from the atmosphere during photosynthesis.

Young forests also take up atmospheric carbon as they grow. Schlesinger, who has been involved in a large-scale project investigating carbon-uptake by forests, is not convinced that reforestation will play a significant role in stabilizing rising levels of carbon dioxide. “The CO2 sink that young forests provide is simply not enough to offset our current fossil fuel emissions. Not by a long shot,” comments Schlesinger.

In the end, Schlesinger urges that if we want to abate environmental ills such as climate change, we need to minimize our impact on biogeochemical cycles. Increasingly, this means changing our current model of energy dependence.

“Forests and cornfields will not save us from the climate-repercussions of our fossil fuel addiction,” Schlesinger notes. Adding that, “the real solution lies in taking immediate actions to curb our fossil fuel emissions.”

Source : Institute of Ecosystem Studies