Eutrophication: impacts of excess nutrient inputs on freshwater, marine, and terrestrial ecosystems

In the mid-1800s, the agricultural chemist Justus von Liebig demonstrated s trong positive relationships between soil nutrient supplies and the growth yields of terrestrial plants, and it has since been found that freshwater a nd marine plants are equally responsive to nutrient inputs. Anthropogenic i nputs of nutrients to the Earth's surface and atmosphere have increased gre atly during the past two centuries. This nutrient enrichment, or eutrophica tion, can lead to highly undesirable changes in ecosystem structure and fun ction, however. In this paper we briefly review the process, the impacts, a nd the potential management of cultural eutrophication in freshwater, marin e, and terrestrial ecosystems. We present two brief case studies (one fresh water and one marine) demonstrating that nutrient loading restriction is th e essential cornerstone of aquatic eutrophication control. In addition, we present results of a preliminary statistical analysis that is consistent wi th the hypothesis that anthropogenic emissions of oxidized nitrogen could b e influencing atmospheric levels of carbon dioxide via nitrogen stimulation of global primary production. (C) 1999 Elsevier Science Ltd. All rights re served.