The widespread use of nitrogen-based fertilizer in recent decades has introduced massive amounts of reactive nitrogen compounds into the environment. Few people know more about the problems this causes than UVA environmental sciences professor James N. Galloway, who has developed the “nitrogen cascade,” a flow chart demonstrating the pervasive effects of reactive nitrogen.
Galloway’s work earned him the 2008 Tyler Environmental Prize, which is administered by the University of Southern California and is considered the equivalent of the Nobel Prize in the fields of environmental science, energy and environmental health.
Galloway’s cascade model describes the sequential impact of reactive nitrogen. A nitrogen atom that begins as part of a smog-forming compound may then be deposited in lakes and forests as nitric acid, which can kill fish and insects. Carried out to coastal areas, the same nitrogen atom may contribute to red tides and dead zones. Finally, the nitrogen may return to the atmosphere as part of the greenhouse gas nitrous oxide, destroying atmospheric ozone.
“We’re accumulating reactive nitrogen in the environment, and this is as much of a legacy as putting carbon dioxide in the atmosphere,” Galloway says. “The public doesn’t know about nitrogen, but in many ways it’s as big an issue as carbon, and due to the interactions of nitrogen and carbon, makes the challenge of providing food and energy to the world’s peoples without harming the global environment a tremendous challenge.” Galloway and others have suggested possible approaches to minimizing nitrogen use, such as optimizing its absorption by plants and animals, recovering and reusing nitrogen from manure and sewage and decreasing nitrogen-intensive livestock farming.