June 23, 2012 – SOUTH-EAST of New Orleans, where the Mississippi empties into the Gulf of Mexico, the North American land mass does not end so much as gently give up. Land subsides to welts of green poking up through the water, and the river grows wider and flatter until it meets the ocean, where a solid line divides the Mississippi’s brown water from the gulf’s blue.
On its long journey south the water has scooped up nutrients such as nitrogen and phosphorus, mainly from the fields of the Midwest. So much so that agriculture’s gift to the gulf is a “dead zone”. The excess nutrients cause algae to bloom, consuming all the available oxygen in the sea, making it hostile to other forms of marine life. Creatures that can swim away, such as shrimp and fish, do so; those that cannot, die. In the four decades since the dead zone was discovered it has grown steadily. Today it covers 6,700 square miles, an area larger than Connecticut.
This ecological disaster area imperils the region’s commercial and recreational fisheries, worth around $2.8 billion a year. One study suggests yearly shrimp-fishery losses of nearly 13%. The dead zone drives shrimp farther out to sea, making it costlier and more time-consuming to catch them. It also makes them smaller.
Nancy Rabalais, who heads the Louisiana Universities Marine Consortium and has mapped the dead zone each year for nearly three decades, claims that the amount of nitrates flowing into the Gulf of Mexico has increased by up to 300% over that time. Most of this comes from agriculture in the “I”-states (Illinois, Iowa and Indiana) and some from the city of Chicago.
It would be a mistake, though, to think that the problem is confined to the Gulf. The effects of nutrient pollution are increasingly apparent throughout the Mississippi River basin. Environmentalists say that half the streams in the upper Mississippi have too much nitrogen and a quarter have too much phosphorus. This nutrient enrichment damages aquatic life there too, and degrades drinking water. It also causes blooms of toxic algae that have closed beaches, made people ill and killed fish and pets. Nasty green lakes have also damaged tourism, property values and fisheries.
For years green groups have been trying to persuade the Environmental Protection Agency (EPA) to set a limit for the amount of nitrogen and phosphorus allowed in the states whose rivers feed the Mississippi. Little has happened. So in March members of the Mississippi River Collaborative, an environmental group, filed a lawsuit designed to force all those involved to think about ways to solve the problem.
Read the full story at the Economist.