SAB Report On Hypoxia In The Northern Gulf of Mexico

Jan 7: U.S. EPA's Science Advisory Board has released a massive 333-page update report entitled, Hypoxia in the Northern Gulf of Mexico: An Update by the EPA Science Advisory Board. Over a year ago, EPA's Office of Water (OW) asked the Science Advisory Board (SAB) to evaluate the most recent science on the hypoxic zone in the Gulf of Mexico as well as potential options for reducing the size of the zone. The hypoxic zone, an area of low dissolved oxygen that cannot support most marine life, has been documented in the Gulf of Mexico since 1985 and was most recently measured at 20,500 km2. The SAB was asked to address the science that has emerged since the 2000 publication of, An Integrated Assessment: Hypoxia in the Northern Gulf of Mexico (Integrated Assessment), the seminal study by the Committee on Environment and Natural Resources that served as the basis for activities coordinated by the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force.

The SAB was also asked to address the most recent science on water quality in the Mississippi Atchafalaya River Basin, an area of 31 States and Tribes that drains approximately 40% of the contiguous United States. Further, the SAB was asked to discuss options for reducing hypoxia in terms of cost, feasibility and social welfare. To address this question, the SAB found it necessary to discuss recent research on water quality as well as research on policy options, in particular, those policies that create economic incentives.

Following OW’s request, the Science Advisory Board Staff Office convened an expert panel under the auspices of the chartered SAB. The SAB Panel consisted of 21 distinguished scientists from academia, industry and government agencies with expertise in the fields of oceanography, ecology, agronomy, agricultural engineering, economics and other fields. Over the past year, the SAB Panel held numerous public meetings and considered information from invited speakers as well as over 60 sets of public comments in the development of this report.

In issuing the report, the SAB reaffirms the major finding of the Integrated Assessment, namely that contemporary changes in the hypoxic area in the northern Gulf of Mexico are primarily related to nutrient loads from the Mississippi Atchafalaya River basin. If the size of the hypoxic zone is to be reduced, the SAB finds that a dual nutrient strategy is needed that achieves at least a 45% reduction in both riverine total nitrogen flux and riverine total phosphorus flux. The SAB offers these as initial targets while stressing the importance of moving in a directionally correct fashion and adjusting policy adaptively on the basis of future data, changing conditions and lessons learned. Climate change will likely contribute to changing conditions. A number of studies have suggested that climate change will create conditions where larger nutrient reductions, e.g., 50 – 60% for nitrogen, would be required to reduce the size of the hypoxic zone. An adaptive management approach, coupling nutrient reductions with continuous monitoring and evaluation, can provide valuable lessons to improve future decisions.

The SAB was asked to comment on the Task Force’s goal of reducing the size of the hypoxic zone to 5,000 km2 by 2015. With respect to the time frame, the SAB finds that such a significant reduction is not likely to be achievable over the next eight years. We conclude this for two reasons. First, there is limited current movement to implement policies, programs and strategies that reduce nutrients. Second, there are time lags between reductions in nutrient inputs and the response of the ecological system. Hence, while the 5,000 km2 target remains a reasonable objective in an adaptive management context; it may no longer be possible to achieve this goal by 2015. SAB says this makes it even more important to proceed in a directionally correct fashion to manage factors affecting hypoxia than to wait for greater precision in setting the goal for the size of the zone.

SAB finds that to reduce hypoxia in the Gulf, a systems view, looking at all sources and effects, is needed. The SAB urges the Agency to consider its options with respect to both non-point and point sources. Non-point sources have long been acknowledged as the primary source of nutrient loadings, however the SAB finds point sources are a more significant contributor than previously thought. Atmospheric deposition of nitrogen is also playing a role in hypoxia.

Access the complete report which includes an executive summary (click here). [*Water]