of the country (Smith and Smith, 2006). These data, along with knowledge of the carbon ratio in biomass, can be used to calculate carbon sequestered in forests. In marine systems, production function approaches have been used to study the productivity of fisheries as a function of ecosystem conditions (Lynne et al., 1981; Kahn and Kemp, 1985; Ellis and Fisher, 1987; McConnell and Strand, 1989; Swallow, 1994; Parks and Bonifaz, 1997; Barbier and Strand, 1998; Barbier, 2000, 2003; Sathirathai and Barbier, 2001; Barbier et al., 2002) although there is far greater uncertainty in the functional relationship between habitat conditions and fishery productivity.

Table 2.1 to include data collection and analyses necessary to establish ecological production functions for two key ecosystem services in the Gulf of Mexico, hazard moderation (in the form of storm protection) and food (in the form of nursery habitat for fisheries). While in general a greater amount of vegetation or animal material (e.g., mangroves and oyster beds) will lead to greater dissipation of wave energy and provide more protection from coastal storms, the degree of protection will depend upon the timing of storms relative to the tide, height of the storm surge, the direction of the wind, speed of passage, and other factors. For many marine species, survival of larvae will depend upon water column conditions and currents at the time of spawning and quality and quantity of nursery habitat leading to highly variable recruitment from year to year.

Finding 4.1: Additional sampling and analyses could facilitate an ecosystem services approach by identifying the impacts on ecosystem function and structure that in turn affect the ecosystem services provided. The collection of these additional data would set the framework for establishing the impact of the spill on ecosystem services.

An example of an ecological production function for a key ecosystem service provided by coastal wetlands—hazard moderation (via storm surge protection)—is provided below (Box 4.1). This example outlines the challenges faced by those seeking to capture the full suite of ecosystem services in a complex environment, as well as the potential benefits of this broader view in assessing the impact of damages to the environment.

For many other ecosystem services, there is either a lack of mechanistic understanding, a lack of data, or both that prevents accurate quantification of ecosystem services as a function of ecosystem condition. Marine ecosystems are complex with many interacting processes and complex food-web dynamics. Such complexity makes it difficult to understand how disturbances



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