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III. Scientific Basis for Goals and Management Options. The Task Force has stated goals of reducing the 5-year running average areal extent of the Gulf of Mexico hypoxic zone to less than 5,000 square kilometers by the year 2015, improving water quality within the basin and protecting the communities and economic conditions within the basin. Additionally, nutrient loads from various sources in the Mississippi River basin have been suggested as the major driver for the formation, extent and duration of the Gulf hypoxic zone.
A. Are these goals supported by present scientific knowledge and understanding of the hypoxic zone, nutrient loads, fate and transport, sources and control options?
The SAB Panel affirms the major findings of the Integrated Assessment. Although the 5,000 km2 target remains a reasonable endpoint for continued use in an adaptive management context; it may no longer be possible to achieve this goal by 2015. Accordingly, it is 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.
i. Based on the current state-of- the-science, should the reduction goal for the size of the hypoxia zone be revised?
No. As discussed in the Executive Summary, it is more important to begin to move in a directionally correct fashion than to refine the goal for the exact size of the hypoxic zone.
ii. Based on the current state-of-the-science, can the areal extent of Gulf hypoxia be reduced while also protecting water quality and social welfare in the basin?
Social welfare can be protected by choosing policies that incorporate targeting, provide economic incentives and maximize co-benefits. As discussed in Section 4.3, improvements in large-scale integrated economic and bio-physical models are needed to better capture system-wide response and effects.
B. Based on the current state-of- the-science, what level of reduction in causal agents (nutrients/discharge) will be needed to achieve the current reduction goal for the size of the hypoxic zone?
As discussed in Section 4.2, to reduce the size of the hypoxic zone, the SAB Panel recommends an adaptive management approach targeting at least a 45% reduction in discharges of total N and total P from the 1980 – 1996 fluxes.
C. Given the available literature and information (especially since 2000) on technologies and practices to reduce nutrient loss from agriculture, runoff from other non-point sources and point source discharges, discuss options (and combinations of options) for reducing nutrient flux in terms of cost, feasibility and any other social welfare considerations.
In general, the social costs of reducing nutrients will vary widely with the policy chosen, hence overall cost-effectiveness is largely a function of policy. Policies that target and provide economic incentives are essential to minimize costs. A wide range of policy options are discussed in Section 4.4, while management options are covered extensively in Section 4.5.
These options may include:
i. the most effective agricultural practices, considering maintenance of soil sustainability and avoiding unintended negative environmental consequences.
The cost and reduction efficency rankings of agricultural management practices will vary by site and region, historic land use and management, depending on crops grown, local soil conditions, distance to waterway, field slopes and configuration, presence of buffers, drainage structures and so forth. Table 16 in Section 4.5.10 provides the SAB Panel’s summary of the evidence comparing the relative effectiveness of nutrient (N and P) reduction options in agriculture. Section 4.5.6 discusses management options for in-field nutrients. A targeted and adaptive management framework will maximize local and regional water quality benefits in the MARB and Gulf.
ii. the most effective actions for other non-point sources
As discussed in Section 4.5.7, there are significant policy opportunities to reduce atmospheric deposition of N, however a detailed examination of air pollution control policy options was beyond the SAB Panel’s scope. Nonetheless, the Panel strenuously recommends incorporating water quality benefits and effects on hypoxia in air pollution control decisions.
iii. the most effective technologies for industrial and municipal point sources.
As discussed in Section 4.5.8, a targeted permit by permit approach to industrial point source discharges could yield significant opportunities for nutrient (N and P) reduction since frequently a limited number of permitted facilities are responsible for a large part of the N and P loads. Municipal point sources are also discussed in Section 4.5.8 where the SAB Panel recommends an analysis to assess the cost and feasibility of tightening limits on N and P concentrations in discharges for large sewage treatment plants.
In all three areas, please address research and information gaps (expanded monitoring, documentation of sources and management practices, effects of practices, further model development and validation, etc.) that should be addressed prior to the next 5-year review.
Recommendations for monitoring and research are found in nearly every section of the report and are included below in the summary of the SAB Panel’s recommendations.
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