Major oil-spills, such as occurred following the grounding of the tanker Exxon Valdez in March 1989 in Prince William Sound, Alaska, account for only a small fraction of the total anthropogenic input of petroleum to the marine environment. Yet major spills can result in significant and even acute impacts, trigger ecological changes requiring decades for recovery, and command considerable public attention. Thus catastrophic oil-spills in general, and the Exxon Valdez spill in particular, differ from other chronic human alterations of coastal marine systems.
Estimates of the fate of the 38,000 metric tons of crude oil lost by the Exxon Valdez are imprecise, but perhaps 30–40% evaporated, 10–25% was recovered, and the rest remains in the marine environment. Roughly 1,500 km of coastline were oiled in varying degrees. Much of this coastline consists of gravel beaches into which oil penetrated to depths as great as 1 m.
The ecological effects of the spill on the marine environments of Prince William Sound and adjacent coastal areas of the Gulf of Alaska were extensive, but natural recovery, aided by clean-up efforts, is expected. Judging by the consequences of other oil-spills affecting rocky shorelines, as well as previous natural and anthropogenic disturbances to Prince William Sound, it appears likely that most affected biotic communities and ecosystems will recover to approximately their pre-spill functional and structural characteristic within from five to twenty-five years.
This oil-spill had major social effects. Many individuals, whether personally present or viewing the spill around the world on television, were saddened by the environmental damage, and felt that an important public trust had been broken. These feelings, together with dissatisfaction with the results of early clean-up efforts, gave rise to popular sentiment in favour of every possible clean-up and mitigation effort — regardless of cost, effectiveness, or possible negative consequences.
The response to the Exxon Valdez oil-spill by government and the oil industry revealed serious inadequacies in the plans and institutions for dealing with major marine oilspills in the United States. Attempts to recover spilled oil, and to respond to the spill's environmental consequences, were hampered by a low level of preparedness and lack of clear agreement about the goals of response efforts. Attempts are under way to improve oil-spill prevention and response capabilities in Alaska and the rest of the United States. However, these efforts are not yet complete, and it remains to be seen whether an improved response will be made to the next major oil-spill.