Nitrogen rivals CO2 as climate threat
August 15th, 2007 by Jim JustNitrogen pollution is the biggest global change that nobody has ever heard of. Changes to the nitrogen cycle are larger in magnitude and more profound than the changes to the carbon cycle, but the nitrogen cycle is being neglected. Now the Ecological Society of America has released a study titled Human Alteration of the Global Nitrogen Cycle: Causes and Consequences (PDF), which examines the impacts of human domination of the nitrogen cycle.
An inert form of nitrogen, N2, actually comprises about 80 percent of the Earth’s atmosphere. Nature on its own does create “reactive nitrogen” – on a limited basis. But in the early 20th century, two scientists found a way to convert inert nitrogen in the air into fertilizer [the Haber-Bosch process]. The invention revolutionized agriculture, lifting limits on food production and allowing the human population to expand exponentially.
Copious amounts of fertilizer are now used in agriculture, with the excess draining into rivers, lakes and the ocean. Combustion of gasoline, natural gas and coal also releases enormous quantities of nitrogen-based compounds into the atmosphere, much of which settles on land and water. Animal waste is another major source of nitrogen. The result? The planet has never seen this much nitrogen at any time. Human activity now releases 125 million metric tons of nitrogen from agricultural activities and fossil fuel combustion a year, compared to 113 million metric tons annually from natural sources.
Nitrous oxide (N2O) is especially worrisome, as it lingers in the atmosphere for a century and is 300 times as potent a heat-trapping gas as carbon dioxide. We won’t solve global warming without addressing nitrogen.