Solutions for a nitrogen-soaked world

Overabundance of an essential nutrient is not always a good thing. – by Liza Lester, ESA communications officer. A tractor spreads manure. Excess fertilizer seeping out of fields has a host of consequences for ecological systems and human health. Credit, flickr user eutrophication&hypoxia, 2010.   NITROGEN is both an essential nutrient and a pollutant, a byproduct of fossil fuel combustion and a fertilizer that feeds billions, a benefit and a hazard, depending on form, location, and quantity. Agriculture, industry and transportation have spread nitrogen liberally around the planet, say scientists in the latest edition of ESA’s Issues in Ecology series, with complex and interrelated consequences for ecological communities and our dependence upon the resources they provide, as well as for human health. Nitrogen is a basic component of life’s most famous molecules: proteins, RNA and DNA. Though nitrogen fills 78.1 percent of the air we breathe, energy is required to convert (or ‘’fix”) it into biologically accessible forms, a process that some species of bacteria can accomplish, but other organisms cannot. Consumers like humans, cows, birds and mosquitoes get nitrogen by eating other live things. For plants, lack of nitrogen in their immediate environment can be a serious limitation. In many ecosystems, the limit of available nitrogen is the limit of growth. We have removed that limit for our food crops by supplying them with fertilizer in the form of manure, nitrogen-“fixing” bacteria symbiotic with legumes like soybeans, and synthetic nitrogen fertilizers. Pulling from a broad pool of expertise in air quality, agronomy, ecology, epidemiology and groundwater geochemistry, the sixteen authors track nitrogen through its different chemical forms and biological incarnations as it progresses across economic, environmental and regulatory bounds. They argue for a systematic, rather than piecemeal, approach to managing the resource and its consequences. “We’re really trying to identify solutions,” said lead author Eric Davidson, a soil ecologist and executive director of the Woods Hole Research Center. “This is a paper about how much we <em>do</em> know, not about what we don’t know. We know about nitrogen cycles, and sources, and we know problems can be addressed in economically viable ways.” In the mid-twentieth century, widespread adoption of the Haber-Bosch industrial process for “fixing” nitrogen from the air using fossil fuels (natural gas, usually) changed agriculture in the US, and there is no going back. There are seven billion people on Earth. Without synthetic nitrogen, author Jim Galloway, a biogeochemist at the University of Virginia, estimates we could feed about four billion. “There are a variety of impacts due to the human use of nitrogen. The biggest is a positive one, in that it allows us to...

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Nutrient enrichment linked to diseases in humans and wildlife

Scientists have provided a rather grim prognosis for global health: the recent increase in nutrient enrichment due to human activities, such as nitrogen pollution through fossil fuel combustion, is likely contributing to several varieties of infectious diseases in humans and wildlife.

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