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Nitrogen Saturation

Human activities have doubled the cycling of nitrogen in the earth's system. Four-fifths of nitric oxide emissions worldwide now come from human activities such as the combustion of fossil fuels, cultivation of certain crops, and especially the manufacture of nitrogen-rich fertilisers. The amount of industrially-fixed nitrogen applied to crops during the decade from 1980 to 1990 more than equals all that applied previously in human history (Pearce, 1997a). Nitrogen saturation causes eutrophication in coastal waters, urban smog, the death of trees, the leaching of nutrients from soils and the loss of fragile heaths. Symptoms of eutrophication (the process of over-fertilization whereby an aquatic or marine ecosystem may lose much of its natural capacity to support a wide variety of vegetation and wildlife) include toxic algal blooms, loss of fish habitat, hypoxia and anoxia, changes in species composition of plankton, elimination of entire food chains, and the death of fish and shellfish (Sea Technology, Dec 1996 & Jan 1997).

References and Sources

Pearce, Fred. 1997a. "Planet earth is drowning in nitrogen". New Scientist, 12 April 1997. P10.

Sea Technology. 1997. "New study provides view of coastal water quality". Sea Technology, January 1997, p65.


Emerging Issues


UNEP/DEWA/Earthwatch 1996-2003