Dead Zones: First in Wisconsin, then the Gulf of Mexico

NPR’s Morning Edition had a short story on the largest dead zone in the Gulf of Mexico’s history. A dead zone is when algae grow quickly enough to monopolize the dissolved oxygen in a body of water. Fish flee this zone and those small or stationary aquatic animals that cannot swim away may die. Dead zones are not a naturally occurring phenomenon. They are caused by agricultural fertilizer runoff.

A few months ago the Yahara River, near the institute, was green and frothy with blue-green algae. This strikingly blue water belied a toxic environment that killed fish and caused hazards for any other animal that interacted with it, including humans. The University of Wisconsin–Madision’s Center for Limnology, which studies surface water, published an in-depth blog post about this toxic algae bloom. This was in late June. This summer has been one of the wettest on record here in Wisconsin and across the Midwest. This increases the runoff of agricultural fertilizers. As a rule of thumb, 50 percent of conventionally applied fertilizer is not absorbed by plants, but washed out into the nearest body of water. I noticed many ponds choked with algae while riding my bike around southern Wisconsin. Once hitting a stream or river, those nutrients are on a downstream trip to the Gulf of Mexico (that is, for most of the Midwest, which is part of the Mississippi watershed).

As we are concentrated on examining how to remove fossil fuels from our subsistence practices, we should note that this is a result of fossil-fuel-driven industrial agriculture. Fertilizes are created using huge amounts of energy to concentrate atmospheric nitrogen into plant-soluble forms. They are transported and applied using diesel trucks and tractors. This type of system is only possible because of the liberal use of a finite resource. As fossil fuels become more expensive, it will be necessary to use fertilizers more judiciously. It is really a shame to waste fertilizers in a one-way waste stream: once turned into plant-soluble forms, they are “stuck” in that form for a while and could be recycled by agricultural practices that create a circle of nutrients: plants → consumption → compost → plants . . .


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