LUMCON’s Gulf of Mexico Shelf Cruise of 2013 was completed last weekend and the final numbers are in for this summer’s hypoxic zone– 5800 square miles. While smaller than predicted based on earlier measures of nutrient loading and rainfall, this is still a huge area. It’s larger than the average hypoxic zone for the last five years. It’s larger than the state of Connecticut. Check out the figures below from the 2012 and 2013 LUMCON hypoxia press releases. (Remember that the 2012 hypoxia zone was one of the smallest on record due to the severe drought.)
The oxygen levels in the dead zone area cannot support aerobic life. Sure, some fish can swim away, but not all aquatic life have the luxury of relocation. For example, some bottom-dwelling fishes and crabs cannot inhabit this area. These species are unsuited for life closer to the surface and consequently must evacuate to other areas of the gulf shelf. This imbalance in biological diversity places a huge stress on the ecosystem in this area- it may not be as simple as ‘everything will come back once the hypoxia dissipates.’ This level of recurrent hypoxia will leave scars on the ecosystem and sustained environmental pressures that some species may not be able to ultimately overcome. Scientists are only beginning to relate the hypoxia zone with effects on the animal species that would otherwise live there. So far there has not been a reported decline in the commercial fishing industry in the Gulf, but such sustained pressures on the ecosystem may eventually trickle up to that level.
Finally, the number 5800 square miles is still greater than twice the Mississippi River/Gulf of Mexico Nutrient Task Force Action Plan Goal of ~2100 square miles. In order to reach this goal, significant decreases in nutrient loading must occur (meaning using less fertilizers and dumping less nitrogenous waste upstream in the watershed). Corn accounts for 40% of all fertilizer use in the US. It requires more nitrogen fertilizer than any other crop, both in per acre usage rate and total consumption. By these numbers, our all-American supercrop contributes significantly to the nutrient runoff fueling the hypoxic zone in the Gulf. The Fertilizer Institute, an advocacy group for the fertilizer industry, has data that shows an 87% increase in corn yield with a -4% fertilizer use spanning the years from 1980 and 2010. In other words, the amount of corn produced per acre has nearly doubled over this time span, while the fertilizer use has decreased. For a variety of reasons, growing corn has, in fact, become more efficient with respect to fertilizer use. However, the total amount of fertilizer used in the US (holding steady around 22 million short tons with some variations due mostly to economic factors) has not seen a significant decrease because of the increase in acres of corn production. According to the USDA, the number of acres of corn planted in 1980 (84 million) to 2013 (97.4 million) has increased by 15%. This has been driven in part by demands from the energy sector (and public policy) to grow corn for ethanol production.
The Nutrient Task Force is working on a number of different fronts to combat the hypoxia problem including developing new strategies for fertilizer efficiency for farmers, reducing industrial pollution, restoring wetland habitats within the watershed, supporting scientific monitoring of the hypoxic zone and increasing public awareness of these interconnected issues. You can read more about it in their report here. Supporting the science to connect these complicated relationships is the lynchpin for the entire project. Once we have a better handle on how different nutrient factors and environmental conditions contribute to hypoxia, the Task Force will be able to form more clearly defined nutrient reduction goals that agriculture and industry can realistically work toward.