The Evaluation of Deepwater Horizon's Environmental Toll (Challenges of a Novel Oil Spill)

In recent months there’s been a lot of talk about how the spill “wasn’t so bad.”  My question to that is…By what, or whose, evaluation?

Right now, what we do know about the spill’s impacts is striking.  And just as striking are the unanswered questions and possible repercussions we won’t have any sense of for some time. 

So, in order to offer some clarity to both what’s known and unknown, here are some examples of both.

What We Know:

  • The blowout killed 11 workers at sea; their families will never be the same.
  • Approximately 170 million gallons of oil was spilled into the Gulf – fifteen times the size of the Exxon-Valdez disaster (note: the total output of oil was estimated to be 205.8 million gallons +/- 10%.  However, because some of the oil was siphoned to boats, only approximately 170 million gallons entered and contaminated the environment).
  • 650 miles of coastline were oiled (note: an estimated 126 miles were moderately to heavily oiled). 
  • Oil settled into wetlands and estuaries around the Gulf Coast, some of the most diverse and productive ecosystems anywhere, killing marsh grass, accelerating erosion and damaging the cradle of the Gulf, the place young fish, shrimp and crabs rely on in the earliest part of their lives.
  • By the government's own reckoning, removal (i.e., burning and skimming) got rid of just 8% of the oil from the BP blowout.  That leaves approximately 92% contaminating the environment, where it evaporated, dispersed or dissolved in the water, floated to the surface, smothered coastal wetlands, beaches and estuaries or sank to the bottom of the sea.
  • 87,000 square miles – approximately 35% - of American Gulf waters had to be closed to fishing – putting thousands of watermen out of work.
  • Arguably a year’s worth of revenue was lost for many people in fisheries and tourism industries (the oil spill overlapped with their main seasons).
  • Residents along the coast - particularly fishermen who rely on the ocean for their livelihoods - have also suffered severe anxiety and social stress.  Experts have observed that the social-fallout from man-made disasters is often more severe and long-lasting than that of natural disasters (for numerous reasons man-made disasters results in more social division).
  • The oil killed wildlife - birds by the thousands, dolphins and whales, fish and hundreds of endangered sea turtles. And that's just the acute impacts that officials were able to observe.
    • Approximately 6000 dead birds were collected in and around the spill this spring and summer with the true death toll likely to be much higher (and yet to be estimated).  The cause of death is still being determined for some fraction of these birds.
    • Approximately 600 sea turtle carcasses were found, a spike in mortality many times higher than usual.  Approximately half of the deaths are believed to be related to the oil spill.  278 loggerhead turtle nests were relocated.
    • As many as 100 marine mammals were found dead.  The cause of death is still being investigated.  However, many more are believed to have gone uncounted as dead marine mammals sink out of sight quickly.

But those numbers are from Chapter 1 of a fable that will unravel for years to come.  There will undoubtedly be an enduring toll on the Gulf.  And here’s some of what remains to be revealed…

  • How many vulnerable baby fish, oysters, shrimp and crabs survived the spill?
  • How much oil is on the bottom of the sea?
  • What harm has it done to deep sea communities? 
  • How long will it persist?
  • What's happened to important fish habitat, from seagrass beds and coral to giant floating sargassum islands?
  • Are toxic elements of the oil getting into the food chain?
  • How badly has this hurt populations of fish like the bluefin tuna, which are already in danger of extinction?

The Deepwater Horizon blowout was a unique ‘oil spill’ in many ways.  The event occurred offshore and in deep water and was responded to with an unprecedented application of chemical dispersants.  As a consequence, the ecological toll will differ from that of a near-shore, surface spill, such as the Exxon Valdez.  The Gulf Coast was significantly affected (in terms of both social and environmental impacts), though, a lot of the harm was directed to the marine environment.  The evaluation of this impact will require innovative research and considerable time. 

It will take years to answer the outstanding questions. That's the job of the Natural Resource Damage Assessment Process, overseen by the National Oceanic and Atmospheric Administration, in concert with other federal, state and local agencies. They need the time and resources to do the job right.

From the earliest days of the BP blowout the catastrophe has been compounded by official information that was incomplete, contradictory or just plain wrong. Uninformed or premature comments about impacts only add to the confusion at this point, further undermining public confidence and contributing to the risk that the nation won't learn the essential lessons of this disaster. 

It is simply too soon to characterize the extent of damage from this spill.  And, we owe it to the Gulf Coast residents to do a complete damage assessment.  

About the Authors

Lisa Suatoni

Senior Scientist, Oceans program

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