Earth's growing nitrogen threat

Mark Clayton in the Christian Science Monitor:… Farmers from [the United States,] China, Europe, and South America rely on nitrogen … to make ends meet and feed a growing world. Yet it’s also becoming clear that too much of a good thing can have a downside for the environment. The world is awash in man-made “reactive” nitrogen (the chemically active form), researchers say.

While greening farms worldwide, much nitrogen washes into lakes, rivers, and the sea, causing rampant algae growth. More nitrogen billows from power-plant smokestacks, blowing in the wind until it settles as acid rain. Still other nitrogen gases remain in the atmosphere consuming the ozone layer. Nitrous oxide is nearly 300 times as potent as carbon dioxide – considered the leading cause of climate change – and the third most threatening greenhouse gas overall.

Last year, reactive nitrogen was identified as one of nine key global pollution threats and second worst in terms of having already exceeded a maximum “planetary boundary,” according to a study reported in the journal Nature.

“Nitrogen plays a tremendously important role in feeding the world’s peoples, so that’s a very positive benefit for humanity,” says James Galloway, a professor of environmental science at the University of Virginia, Charlottesville, and a leading nitrogen researcher. “The problem is how to maximize nitrogen’s benefits while diminishing its negatives – especially waste.”

… But the most dramatic impacts can be seen in the growth of coastal dead zones where excessive nutrients in the water – fueled by runoff of fertilizers – has suffocated or driven away ocean animals. In the Gulf of Mexico, fish and shrimp have been eliminated in an 8,000-square-mile dead zone at the mouth of the Mississippi River. More than 400 dead zones with a total area of 245,000 square kilometers were identified worldwide last year….

A large bloom of cyanobacteria, more commonly known as blue-green algae, spread across Guatemala's Lake Atitlán in green filaments and strands that are clearly visible in this simulated-natural-colour image, via NASA