A fisherman carries a bird coated with oil that spilled from the Exxon Valdez tanker that ruptured off of the Alaskan coast.

Chris Wilkins/Getty Images

The Number One Environmental Disaster: Exxon Valdez

Ironically, the worst environmental disaster in history was an oil spill that doesn't even rank among the top 50 largest oil spills [source: Lovgren]. Yet the Exxon Valdez oil spill is widely considered to be the most disastrous oil spill in the world in terms of its environmental impact [source: Exxon]. The 11 million gallons (or 257,000 barrels) of oil that eventually escaped from the tanker's hull continue to affect the surrounding area [source: Lovgren]. As soon as the ship hit Bligh Reef, the Alaskan body of water known as Prince William Sound became forever changed.

As you might remember, the Exxon Valdez oil tanker left Alaska on March 23, 1989, at 9:12 p.m. carrying more than 53 million gallons (1.26 million barrels) of oil. Just three hours later, after the ship ran into a reef, thousands of gallons of oil coated everything within site. All told, the amount of oil spilled was enough to fill an Olympic-sized swimming pool 125 times [source: Exxon]. While 11 million gallons was the official number given by the U.S. Coast Guard at the time, some people involved in the cleanup effort estimate that the amount of oil spilled was nearly three times that [source: Knickerbocker].

Despite the relatively small amount of oil released, several factors contributed to the spill's severity: timing, location, abundance of wildlife and substandard cleanup efforts. In comparison, one of the largest oil spills in history, the rupture of an oil well in the Gulf of Mexico that released 140 million gallons (3.3 million barrels) of oil, caused relatively little damage because it happened in the open sea where currents and winds contained it until it disintegrated [source: Stevens].

By contrast, the Exxon spill occurred inside a body of water that housed an abundance of wildlife rather than in the open ocean where oil could dissipate and be broken down by wave action. The following animals were killed by the spill:

  • 250,000 seabirds
  • 2,800 sea otters
  • 300 harbor seals
  • 250 bald eagles
  • 22 killer whales

[source: Knickerbocker]

The 10,000 square miles (25,900 square kilometers) and 1,500 miles (2,414 kilometers) of shoreline covered with oil encompassed a national forest, four wildlife refuges, three national parks, five state parks, four critical habitat areas and a state game sanctuary [source: Knickerbocker].

Ten years later, only two of 23 animal species injured by the oil slicks had fully recovered [source: Knickerbocker]. As of 2004, populations of loons, harbor seals, harlequin ducks and Pacific herring were still affected by the spill [source: Lovgren], and the entire food chain was altered.

Thousands of workers participated in the cleanup efforts, but since little was known about effective cleanup methods, the workers weren't as successful as they could have been. In addition, cleanup didn't begin until three days after the spill, after a storm had spread much of the oil onto the coastline before it could be contained. Despite the cleanup effort, several miles of shoreline are still contaminated, and up to 200 tons of crude oil remain [source: Hoare, National Wildlife]. Even in areas where the surface waters appear clear, oil often lurks beneath the surface in little pockets buried by sediment.

It may take decades for Prince William Sound to heal fully. The oil remaining in the sound is almost the same composition it was decades ago -- an unknown factor has slowed down the rate of oil decomposition to only 4 percent a year [source: Hyder].

­Other events, though less well-known, have done considerable environmental damage as well. Learn about some other ecological disasters next.