Congressional Research Service Report - The Deepwater Horizon Oil Spill Coastal Wetland and Wildlife Impacts and Response
The explosion of the Deepwater Horizon drilling rig in the Gulf of Mexico on April 20, 2010, and the resulting oil spill began a cascade of effects on the coastal areas of the Gulf and on the wealth of species that inhabit those areas, effects that continue even though oil stopped flowing in July and the well was sealed in September. Gulf coast wetlands, like those elsewhere, have value for water quality, flood control, shoreline protection, and recreation. They serve as nurseries for many species, including fish and shellfish of commercial significance, waterfowl, and a host of resident and migratory species. They also have cultural importance to the people of the Gulf. The effects of the spill come on top of historic wetland losses due to subsidence, drainage, and saltwater intrusion, along with rising sea levels, coastal erosion, and global climate change.
Impacts of oil spills on wetland ecosystems depend on multiple factors, including the type of oil, exposure of the oil to weathering factors before it reaches the shore, the season in which the spill occurs, etc. Mitigation and cleanup of damage to wetlands is far from an exact science and involves many tradeoffs; there is no single, best solution. A number of options exist, ranging from mechanical recovery and use of dispersants to doing nothing. Estimating wildlife impacts is particularly difficult in this case because the spill occurred far offshore, and the initial wildlife mortality came far out in the Gulf, where animals sank without reaching the shore. When oil arrived at the shore, more animals began to be counted. Moreover, because the Gulf wetlands host many species of birds during seasonal migrations, impacts of the spill could be felt in areas well away from the Gulf.
Among other issues is a seemingly simple question: who decides what to do when such an event occurs? But the answer is complex. The organizational structure for deciding how to respond to oil spills is specified in the National Contingency Plan (NCP), which was created administratively and has been broadened by the Clean Water Act, the Superfund law, and the Oil Pollution Act. Under the NCP structure, the Coast Guard is the lead federal agency for overseeing response and cleanup. Until oil from the well stopped flowing, very little cleanup of wetlands was occurring, because of both the ongoing risk of greater harm from cleanup and the potential for re-oiling. As cleanup proceeds, a number of questions arise. To cite only two, what factors will determine cleanup strategies, and how are needs to improve scientific understanding of the impacts of oil spills being considered?
Decisions about cleanup of wildlife are no easier. Cleanup of individual animals is labor-intensive, and some scientists argue that the survival of an animal that has been cleaned is so uncertain as to call into question whether treatment is, in fact, humane. Rescue groups are dedicated to salvaging those that can still be saved. The effects on a species as a whole vary markedly from one species to another, depending on that species' abundance and ecological needs; appropriate responses at the species level are unclear.
History, particularly from the relatively well-studied Exxon Valdez spill of 1989, offers insight into the future of Gulf resources as well. First, some cleanup efforts might do more harm than good in the long run. Second, it is not possible to predict all of the ramifications for the complex Gulf ecosystem in the decades to come, but history suggests that at least some effects will continue for decades. Finally, litigation could play a major role in disseminating—or not disseminating—scientific information about the spill and its effects.