Dead Zones in the Gulf: Reaping What is Sown Upriver

The impact of the Deepwater Horizon tragedy will be felt for years in the Gulf region. Ecological and economic impacts in the Gulf aren’t limited to oil drilling, though.

Decisions we make about development patterns and productive uses of land are also causing effects that resonate within the Gulf ecosystem. An oxygen-depleted “dead zone,” at times measured to be about the size of Massachusetts, appears seasonally in the Gulf of Mexico and leads to serious fish kills. The dead zone, or hypoxic zone, results from a combination of excess nutrients and seasonal water stratification. Recent studies have shown that untreated agricultural runoff is one of the leading causes of the hypoxic zone in the Gulf.

But it’s not just agriculture in and around the Gulf of Mexico. The Gulf is fed by the mighty Mississippi, whose watershed incorporates 41% of the land mass of the lower 48 states, from Montana to Pennsylvania and Minnesota to Louisiana. Within this huge river basin are some of the highest concentrations of large-scale agriculture in the U.S. Excess nutrients flowing off of farmland are conveyed down to the Mississippi and end up in concentrated amounts in the Gulf, where algae feast on them. As the algae die and decompose, oxygen is depleted in the water and fish and other sea life cannot survive.

A series of studies in the mid-1990s and early 2000s linked the effects of hypoxia in the Gulf to the farming and agricultural practices in the Corn Belt. These studies also began to explore the potential for dramatic change through innovative, alternative landscape patterns in farming practices, which could provide many benefits and decrease downstream effects in the Gulf. From the Corn Belt to the Gulf: Societal and Environmental Implications of Alternative Agricultural Scenarios, edited by Joan Nassauer, Mary Santelmann, and Don Scavia, brings together these integrated assessments of land use in the Mississippi River Basin and the effects on the dead zone in the Gulf. The book also highlights alternative farming scenarios in two small agricultural watersheds in Iowa. Discussion focuses on the policy implications of alternative farming practices that emphasize ecological restoration and increased biodiversity, while providing new economic opportunity.

For the restoration community, one of the most important points to take from this huge body of work is the implication that there are many benefits that result from alternative landscape patterns that integrate productive use of land with restorative design and planning. With the inclusion of riparian buffers, the restoration of wetlands, the implementation of a more diverse selection of native crops, and the incorporation of natural areas into farming landscapes, we can see a myriad of benefits. These include improved human health, increased environmental health and habitat potential, and improved water quality, while lessening the potential for large flood events and providing new economic drivers. An old aesthetic can become new again, providing more holistically productive landscapes and seascapes, from the upper reaches of the Mississippi all the way to the Gulf.

For more information on the research done on the future Corn Belt agricultural scenarios and hypoxia in the Gulf of Mexico, see the following links:

Joan Nassauer’s Landscape Ecology Perception and Design Lab at the University of Michigan: http://wwwpersonal. umich.edu/~nassauer/rural_sheds.html

The Integrated Assessment by the Task Force on Hypoxia in the Gulf of Mexico: http://oceanservice.noaa.gov/products/hypox_final.pdf

2008 conference proceedings for Hypoxia in the Gulf of Mexico and Implications and Strategies for Iowa: http://www.card.iastate.edu/hypoxia/presentations.aspx