In addition to understanding the provision of services, understanding the value of services in terms of human well-being also poses a number of issues. Economic approaches to valuation offer the promise of measuring benefits from ecosystem services in a common metric (money). However, some ecosystem service benefits are extremely difficult to accurately assess in monetary terms (e.g., spiritual, cultural, and aesthetic values). There are additional concerns over distributional equity: who benefits and who is harmed by changes in ecosystem conditions? Making the public whole via restoration is not simply a matter of making sure that aggregate net benefits with restoration are greater or equal to aggregate net benefits before the oil spill. Making the public whole also involves making sure that aggregate net benefits to various groups within society do not decline. Since many services emanate from public resources, for example national parks for recreation and oyster beds for food, it is important that the benefits of ecosystem services are enjoyed by as many as possible without excluding or negatively impacting one segment of the population.
An ecosystem services approach focuses not only on the restoration of damaged resources, but also on maintaining the usefulness of those resources to the public. On the other hand, an ecosystem services approach that restores the value of the services but does so via human-engineered substitutes (e.g., building a dyke or water filtration plant) will not result in making the environment whole. Some portions of the public may not view such actions as adequate restoration even though the value of services is made equivalent. There is also the danger that an ecosystem services approach will focus on a small subset of services and may not restore the full suite of ecosystem services valued by the public given the difficulty of valuing the complete set of ecosystem services (NRC, 2005a). To the extent that the public values the existence of habitat and species, regardless of the extent that these lead to provision of other ecosystem services beyond existence, the gap in practice between restoring ecosystem services and restoring habitat and species will be reduced. High existence values may mean making the environment whole would be necessary for making the public whole.
We also caution that our discussions have not touched on the issue of public involvement or review of any potential restoration project. It is clear that for the DWH spill public involvement and review will be a key element of decisions on restoration projects. It is likely that the value placed on particular habitats, restoration projects, or natural resources will vary with the community involved, which will add complexity to the overall process. Furthermore, improvements that increase the benefits from one ecosystem