Like crude oil, scientific comparisons can be slippery. Most adult Americans remember the Exxon Valdez tragedy and rescue workers using dish detergent to clean heavily oiled birds. When they first hear that "only" 1,387 dead birds have been collected and tallied so far in the Gulf of Mexico, compared to the estimated bird death toll in the hundreds of thousands from the Exxon Valdez spill, they can be forgiven for thinking that the Alaska spill was worse for wildlife. Unfortunately, that conclusion could be seriously mistaken.
Oil is still gushing into the Gulf of Mexico from the Deepwater Horizon well, and worst-case flow estimates continue to increase. (Today that stands at 100,000 barrels per day, by BP's own admission.) The Deepwater Horizon disaster also presents unique challenges to surveying damages. The Gulf disaster originated 48 miles offshore in a dynamic environment of winds, currents, and migratory pathways. Because the Gulf oil is dispersing over such a large surface and underwater area, birds can be exposed to oil both along the coast and miles from shore and even underwater when they dive for fish. Many wildlife casualties therefore will never be observed and counted.
Still, widespread, systematic surveys and transparent reporting of oil-exposed animals in the wild are urgently needed to assess the damage of the Gulf disaster. A simple count of captured and collected animals does not adequately assess the real wildlife impacts.
We also don't know the long-term eco-toxicity of the chemical dispersants being applied at unprecedented volumes, or the toxicity of the oil-dispersant mix, because little research has been done in this area.
To make a bad situation much worse, millions of migratory ducks, geese, and shorebirds such as sandpipers and plovers are now on their northern breeding grounds and will soon return to the Gulf region. Exposed to crude oil, many will die in Louisiana's wetlands or on the water without large-scale intervention. As the BP oil disaster worsens and these birds return to the Gulf region, the wildlife death toll could skyrocket. Unless a systematic, independent and transparent monitoring and reporting process is established immediately, the public may never know the full toll on animals left to die in the wild.
Birds can die when their feathers are coated with oil, but that's not the only threat. They can also ingest oil, absorb it through their skin, or consume contaminated prey. Wetlands are critical nurseries for invertebrates, fish, and crustaceans and are therefore feeding grounds for many bird species. Internal oil exposure can cause organ damage, reproductive failure, and slow death in the wild. Birds that die in the wild from internal exposure are not reflected in the current BP disaster tally.
The full damage to coastal habitats and the birds that depend on them, including marsh birds, shorebirds, pelicans, raptors, songbirds, and wading birds, is still unknown. But we do know that oil can kill marsh vegetation and persist in sediments and mudflats over time. Consequently, it will take years of monitoring before we know the real magnitude of this disaster.
Birds, of course, are not the only wildlife affected by this disaster. Gulf currents are essentially a superhighway for drifting eggs, larvae, jellyfish, and plankton that form the base of the marine food chain, which supports larger fish, sea turtles, whales and dolphins, and seabirds. We can't yet quantify the impact on coral reefs, mangroves, and other coastal fish spawning areas, but that impact could be devastating to fish populations and the untold numbers of coastal birds that prey upon them.
Finally, these catastrophic results do not include wildlife caught up in response efforts like prescribed oil burns, skimming, vacuuming, coastal clean-up, and chemical dispersants. Also, oil and chemical dispersants may eventually be carried inland via several pathways, including hurricanes and animals that transport oil on their skin, fur, or feathers. Wildlife that consume oil and dispersants and then enter the food chain as prey could contaminate inland predators.
To assess the real damage to fish and wildlife, we need independent, long-term, and widespread surveys that systematically monitor how widely oil from the Deepwater Horizon is being transported, how long it persists, and both short- and long-term impacts to animal populations and the entire food web.
We now have another reason to call for independent, third-party monitoring and transparent reporting of wildlife impacts: the U.S. Fish and Wildlife Service, as reported July 6 by the New York Times, signed off on a weak wildlife risk assessment for this and other Gulf of Mexico deepwater lease sales in 2007. Can the agency that went along with Minerals Management Service's flawed biological assessment of endangered species' risks now be entrusted with accurately accounting for the damages?
In the meantime, we should not use the official tallies of wildlife deaths as a sole metric of the ecosystem damages of the BP oil disaster. Comparisons of official Gulf wildlife death tolls to the Exxon Valdez and other oil spills, at this stage, underestimate the real, widespread and long-term impacts of the Gulf catastrophe. The BP oil disaster will likely be the worst we Americans have ever seen. Until we address the problems of a vulnerable Gulf oil infrastructure and weak safety regulations for offshore rigs, it may not be the last.
Stacy Small is a conservation scientist with the Environmental Defense Fund.