Now that the BP oil well has been plugged, it’s more urgent than ever to address the Gulf Coast “dead zone.”

The dead zone is a huge oxygen-starved region beneath the Gulf Coast surface, caused primarily by agricultural runoff of pesticides and fertilizers.

This seasonal phenomenon usually covers about 5,300 square miles, but in 2008 the zone erupted to cover 8,000 square miles — an area the size of Massachusetts. Fish and other marine life must flee the zone or perish.

Even before BP’s massive oil spill, many Gulf fisheries had already declined or disappeared because of the dead zone.

The Mississippi River is the main conduit for the harmful pesticides and fertilizers. The river gathers water from all or parts of 31 states, and it carries an average annual load of 1.65 million metric tons of nitrogen/phosphorus to the Gulf from farms, fields, yards, public parks and golf courses.

The Upper Mississippi River basin includes southern Minnesota, most of Iowa and parts of Wisconsin, Illinois, Indiana and Missouri. These states account for only 15 percent of the river’s drainage basin, but discharge more than 50 percent of the nitrogen that runs to the Gulf.

Those of us who live in Mississippi River states must do whatever possible to improve the river’s water quality. A range of initiatives aimed at keeping fertilizers and pesticides out of groundwater runoff must be deployed.

A 2008 report issued by the National Research Council of the National Academies, sponsored by the McKnight Foundation, took a careful look at all of the factors adversely affecting water quality in the Mississippi River. The report points to runoff from agricultural land as the primary culprit.

Organic farming is crucial for reducing this runoff.

Organic farming methods, including the use of crop rotation and cover crops, help to improve soil composition, locking nitrogen and other dead-zone nutrients in the ground around plants instead of releasing them in runoff. Organic farmers deploy buffer and filter areas to reduce runoff and erosion. Organic farmers also avoid commercial pesticides and fertilizers, reducing the toxic load that ends up in the Gulf of Mexico.

In short, converting more Midwestern agriculture acres to organic production will help ecosystems and economies downstream.

That help has never been needed more than now. The combination of the BP oil spill and the ongoing runoff of pesticides and fertilizers may be too much for the Gulf ecosystem to handle.

Each of us can take a few simple steps to save that ecosystem.

Reduce or eliminate use of commercial fertilizers and pesticides. Buy organic produce at the store. Purchase directly from organic growers at farmers’ markets. Participate in community-supported agriculture, whereby you pay a farmer at the beginning of the season for produce, and the farmer delivers to you regularly at a central location.

These modest contributions will make a difference.

We can’t allow the Gulf to be destroyed.

Jeff Gunderson is the organics specialist for the Midwest Organic and Sustainable Education Service. He can be reached at pmproj [at] progressive [dot] org.

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