of $19.7 billion per year (National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling, 2011). The wetlands and marshes of the Gulf region play a critical role in storm surge protection (a regulating service) as well as nutrient cycling and water purification (supporting services) and commercial fisheries landings (a provisioning service), which account for approximately 25 percent of the seafood provided by the contiguous United States (NMFS, 2010b). Additionally, the people of the GoM region and the nation as a whole benefit from the vast hydrocarbon resources of the GoM, which, in 2009, accounted for 29 percent of the total crude oil and 13 percent of the natural gas production in the United States (DOE, 2010).

The evolving understanding of human–ecosystem interactions, which is shaped by the concepts of ecosystem-based management and particularly ecosystem services, offers an opportunity to address some of the challenges inherent in assessing the impacts of an event such as the DWH oil spill. By taking a more holistic view of ecosystem interactions and then following these interactions through all relevant trophic levels and spatial connections to their ultimate impact on human well-being, an ecosystem services approach to damage assessment enables formation of a more complete picture of potential impacts and a broader range of restoration options. This is particularly relevant to a spill the size, duration, depth, and complexity of the DWH oil spill, during which oil and dispersants were released at 1,500-m depth into a relatively poorly understood deep-sea ecosystem that includes deep-sea corals and chemosynthetic communities (organisms that derive their energy from oxidizing inorganic molecules). Oil, dispersants, and dispersed oil then traversed through the water column, interacting with fish, marine mammals, and other organisms throughout the trophic web, making their way through the photic zone, and sometimes reaching beaches and salt marshes.

All of this occurred in a region that has been subject to numerous other natural disasters (e.g., hurricanes) and human actions (e.g., levee construction for flood control, fertilizer application) that have created dynamic baselines from which to estimate the impact of the spill. Never before has the United States faced a spill of this magnitude or with the potential to impact all trophic levels of such a complex and dynamic ecosystem. To quantify the spill’s impact we must first understand the interactions and linkages between and among the various components and processes (including human) of this ecosystem. Recognizing these unique and unprecedented aspects of the DWH oil spill and the associated complexity of the task of assessing damages, Congress requested that the National Academy of Sciences evaluate the effects of the DWH oil spill on the ecosystem services of the GoM. A committee was established in January 2011 and charged with addressing the questions posed in the following Statement of Task:

Statement of Task

1.   What methods are available for identifying and quantifying various ecosystem services? What are the spatial and temporal scales conducive to research that provide meaningful information for the public and decision makers?

2.   What methods and types of information can be used to approximate baselines (but-for-the-spill) for distinguishing effects on ecosystem services specific to the spill?



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