On March 24, 1989, the oil tanker Exxon Valdez grounded on a reef in Prince William Sound, Alaska, spilling more than 11 million gallons of crude oil that eventually spread over approximately 11,000 square miles of ocean. Yet the size of this spill pales in comparison to the 2010 BP oil spill—also referred to as the Deepwater Horizon spill—which poured about 185 million gallons of oil into the Gulf of Mexico, covering over 78,000 square miles. The volume of the BP oil spill would fill 145 typical-sized gymnasiums; the Exxon Valdez, only 9. Even so, the Exxon Valdez spill had a huge environmental impact, and may offer some understanding of the eventual ecological toll of the BP spill.

To clean up the oil in Prince William Sound after Exxon Valdez, workers tried three methods: burning, mechanical cleaning (such as skimmers to collect and remove the oil), and chemical dispersants. Despite the extensive cleanup effort, only a small percentage of the oil was recovered. According to the National Oceanic and Atmospheric Administration (NOAA), more than 26,000 gallons of oil remained in shoreline soil nearly a decade after the accident.

Both the long- and short-term effects of the oil spill were enormous. Hundreds of thousands of animals died within the first few months. It is estimated that 100,000 to 250,000 seabirds perished, along with sea otters, harbor seals, bald eagles, orcas, and billions of salmon and herring eggs. Effects from the spill continue to be felt years after the accident. Some animals, such as sea otters, showed higher rates of mortality in the years following the spill, likely a result of ingesting contaminants, and reduced populations of many other ocean animals have been observed. Scientists estimate that it may take up to 30 years for habitats to recover.

Based on this history, what can we expect from the BP oil spill? Mainly that it may take decades to assess the full impact of this disaster. As demonstrated by Exxon Valdez, oil can persist in the environment for many years, and the long-term impacts on fish and wildlife cannot be overlooked. In the Gulf of Mexico, thousands of species of fish, birds, crustaceans, sea turtles, and marine mammals are at risk from the oil itself, as well as from toxic dispersants and loss of habitat. It is still unclear what will happen in the coming decades and how this will affect the Gulf ecosystems and the health and economic welfare of humans who depend upon it.

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