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In the past 10 years, Midwest agriculture has had to come to grips with a disturbing revelation. Commercial nitrogen, the most essential of nutrients and the lifeblood for current agricultural practices, has likely been the primary contributor to a growing zone limited aquatic life in the Gulf of Mexico. This zone of low dissolved oxygen, or hypoxia, is called the hypoxic zone (or sometimes the "dead zone").
Hypoxia occurs as a result of the over-enrichment of nutrients in aquatic environments. Nutrients—primarily nitrogen—stimulate excessive growth of algae, which consume oxygen when they decompose. An area is considered hypoxic when dissolved oxygen levels fall below two parts per million—a level at which few marine organisms can survive.
Hypoxia in the Gulf of Mexico emerged as a national concern nearly 15 years ago. There is some evidence that the hypoxic zone has existed in the Gulf since the 1970s, although much smaller in size than the current zone. Detailed monitoring of the extent of the hypoxic zone began in 1985. While the area and volume of the hypoxic zone has varied, the zone increased from a running average of 8,300 km² in 1985-1992 to over 16,000 km² in 1993-2001. The hypoxic zone peaked at 22,000 km² in 2002. The size of the zone is now roughly the size of the state of Rhode Island. The rapid expansion of the Gulf hypoxic zone has alarmed many fishers and shrimpers, along with ecologists, oceanographers, environmentalists, politicians and upstream farmers.
Gulf hypoxia has significant economic and environmental consequences. Hypoxia is essentially a form of habitat loss, eliminating areas in which fish and other marine organisms can survive. Low dissolved oxygen levels disrupt aquatic life cycles, increase susceptibility to predation and decrease biodiversity. An ecological collapse in the Gulf could put the billions of dollars that Gulf States receive in fishing and tourism revenue at risk.
Additionally, Gulf hypoxia is a powerful indicator that things are amiss in the Mississippi River Basin. It demonstrates that nutrients from farms, septic fields, treatment plants and lawns can not only harm local streams and lakes, but can also impact water bodies thousands of miles away. It demonstrates that wetlands and other land uses that hold water and utilize nutrients have a value beyond wildlife and flood control. Finally, it demonstrates that some of the agricultural practices that now dominate the Midwest, such as limited crop rotation, intensive tile drainage, and heavy dependence on commercial fertilizer, have environmental consequences that are only beginning to materialize.
Fortunately, Midwest agriculture can not only meet these challenges, it can utilize the transition to strengthen its long-term viability. The knowledge and technical skill exist to make the necessary changes to the system, as demonstrated by the promising initiatives of farmers, researchers, scientists, policy analysis, government staff and others.
An increasing number of farmers, for example, are finding ways to increase their profitability with agricultural systems that require minimal tillage and fertilizers, and that can benefit water and soil quality. Examples include grass-fed livestock, raising perennial crops for energy production, and growing alternative crops such as hazelnut trees. Other farmers are growing conventional crops, but are using cover crops, no-till, and innovative nutrient management techniques to limit environmental impacts.
The relationship between agricultural production systems and water quality is well documented. What have not been adequately explored are practical policy and market approaches that can address these issues at a basin-wide scale. RiverMap aims to integrate research, policy analysis, and project-based implementation into a cohesive picture that provides insights into new opportunities for Midwest agriculture and reduces water quality impacts on the Mississippi River and the Gulf of Mexico.
If stakeholders in the Basin act together to coordinate efforts, encourage investment, and promote effective policy, the future of both Midwest agriculture and the Gulf of Mexico will be brighter than ever.
