New map shows nutrient threat to coastal areas

Program #5459 of the Earth & Sky Radio Series
with hosts Deborah Byrd, Joel Block,
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Legend:Yellow=Areas of Concern, Red=Documented Hypoxic Areas, Green=Systems in Recovery. (Data compiled from various sources by R. Diaz, M. Selman and Z. Sugg. Credit: World Resources Institute.) See a larger version of this image.

In 2008, the World Resources Institute in Washington D.C. released a new map showing more than 400 coastal areas worldwide threatened by too many nutrients in watery ecosystems.

This condition is responsible for life-destroying algal blooms and ultimately dead zones like that in the Gulf of Mexico. Scientists call it ‘eutrophication.’

Mindy Selman: We generally think of nutrients as a good thing. But in the case of eutrophication, it’s too much of a good thing. And it wreaks havoc on the ecosystem.

That’s Mindy Selman, a water quality expert at the World Resources Institute. She said that 78% of U.S. coastal areas are eutrophic.

Mindy Selman: We like to say it’s a global problem, but with local manifestations.

She said it happens when nutrient cycles are knocked out of balance by an overabundance of nitrogen and phosphorus. For example, when farmers over-fertilize their crops, the excess nutrients flow into the watershed. Selman said ultimately the issue of excess nutrients is human sustainability issue.

Mindy Selman: It’s a problem that’s very cross-cutting. It has to do with the type of energy that we’re using. It has to do with the way we grow our food and what our diets are. There are going to be no simple fixes to eutriphication.

WRI’s map was based on extensive reviews of scientific literature. The number of eutrophic coastal areas around the world is most likely far greater than 415, according to Selman.

Mindy Selman: The U.S. and Europe have each conducted coastal surveys and have a fairly good idea of the extent of eutrophication. However, in Asia, South America, the Caribbean, and Africa, the data are scarce. This isn’t really an issue they are tackling—the monitoring data aren’t really there. However, there is lots of anecdotal evidence of eutrophication in many of these areas — for example, massive blooms of toxic algae off the coast of China. We also see trends in many countries of increased fertilizer use, increased per-capita meat consumption, increased aquaculture, increased populations on the coast, etc. , that would indicate that eutrophication is almost certainly occurring in these areas.

Mindy Selman on agriculture and eutrophication
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