|John Wiens on a survey of Prince William Sound, circa 1995.|
When I heard about the Deepwater Horizon disaster, I had that déjàvu feeling all over again. Once again an oil spill has fouled our oceans and coasts. Once again we see heart-wrenching images of seabirds struggling helplessly to escape the heavy mantle of black goo. Once again we ask how, in this age of advanced technology, such things can happen. Then, if the past is any guide, the images will fade from our memories, politicians will dither, and stock prices for oil companies will rebound. Our insatiable thirst for fossil fuels will drive us to seek oil in more extreme and riskier environments.
This time must be different.
The Deepwater Horizon disaster brought back memories. More than two decades ago, the tanker Exxon Valdez grounded in Prince William Sound, Alaska, spilling 260,000 barrels of Alaska North Slope crude oil. Within a month I began documenting the spill's impacts on marine birds--and I'm still at it. What I've learned may provide some perspective on the Deepwater Horizon spill and the role of scientists in assessing its ecological effects.
Initial responses to the Exxon Valdez oil spill and the Deepwater Horizon blowout were similar, some disturbingly so. There was a strong emotional response from the public, amplified in the Deepwater Horizon explosion by the loss of human lives. There were concerns about damages to marine life and human livelihoods. There was outrage at "big oil" and a rush to assign blame. Enough lawsuits were filed to keep lawyers busy for years. There were difficulties in mobilizing a response to protect coastal areas, exacerbated by disputes among government agencies and corporate interests. Pundits pontificated. The media flocked to the scene, along with advocates eager to advance their agendas. And scientists were there, too, including some who were all too willing to oblige the media with premature prognostications about long-term environmental damages.
But the two oil spills differ in important ways. First, geography. The Exxon Valdez spill released a large amount of oil all at once onto the surface of icy cold Alaskan waters in an area studded with bays and islands, and an early spring storm pushed the spreading oil onto rocky shorelines, where cleanup operations could be focused. Oil from the Deepwater Horizon continues to spew from deep in the ocean, creating an underwater plume of oil and methane. As oil reached the warm surface waters it spread slowly, reaching land only weeks after the initial blowout. The shoreline of the Gulf of Mexico is dissected by countless bayous, and the beaches are shallow and sandy. Even with a massive effort, cleanup will be difficult.
|Common Murre is among the bird species most affected by the Exxon Valdez oil spill. Photo by Ron LeValley/www.levalleyphoto.com|
Another distinction centers on numbers of animals concentrated near the accidents' epicenters. The Exxon Valdez spill occurred in an area of incredibly abundant wildlife, resulting in the immediate mortality of hundreds of thousands of marine birds and mammals. Within weeks, oiled carcasses of over 35,000 birds and several hundred sea otters had been retrieved; overall, perhaps 250,000 birds and as many as 1,000 sea otters died. It is much too early to project the effects of the Deepwater Horizon spill on wildlife, but two months after the blowout, oiled carcasses of 934 birds, 380 sea turtles, and 46 marine mammals had been retrieved. Although it is doubtful that wildlife mortality will approach that from the Exxon Valdez spill, coastal marshes and estuaries and marine life may be heavily impacted; if the underwater plume of oil causes a crash in phytoplankton production, entire food webs may be imperiled.
The role of scientists in assessing the ecological consequences of environmental accidents such as the Exxon Valdez or Deepwater Horizon is to provide reasoned, objective answers to two questions: "Are there ecological effects?" and "Are the effects we see due to oil, or to something else?" Framing the questions is important. It's easy to ignore the first question (aren't dead birds evidence enough?) and just ask "How bad was it?" This leads one to look only for negative impacts, which may so narrow the focus of investigations that we fail to understand the overall effects. In our studies of the Exxon Valdez spill, for example, we found that marine birds responded to the spill in different ways, with some species reoccupying oiled habitats within a month or two, others taking much longer.
Addressing these questions requires careful attention to research design. We can derive an estimate of overall mortality, extrapolated from the counts of oiled carcasses, but that tells us nothing about the effects on population dynamics or on the use of habitats. Does the immediate mortality by itself translate into long-term consequences, or are there effects on individuals other than mortality which also enter the equation? Do populations recover and, if so, when?
Answering these questions for the Exxon Valdez spill has been difficult and contentious (which is why I'm still at it). One problem is that oil spills are not like carefully planned and controlled scientific experiments. They occur against a backdrop of natural environmental variation, which muddies the waters. In the years before the Exxon Valdez spill, for example, there were major changes in oceanographic conditions and seabird prey, and in subsequent years there were two large El Niño events. Such environmental variations make it difficult to pinpoint whether the differences observed in wildlife populations, in before-after comparisons or between oiled and unoiled places, are due to oil or something else. There are ways to design studies and analyze results to disentangle the effects of variation in space and time, but they must be part of the plan from the outset rather than afterthoughts.
A second problem arises when one tries to determine when or whether species have recovered from the effects of a spill. Is it when abundances return to former levels, when reproduction is normal (whatever "normal" is), when individuals evidence no physiological changes that might be associated with exposure to oil, or something else? As mentioned above, our studies in Alaska indicated rapid re-occupancy of oiled habitats by several seabird species, others taking nearly a decade. By most (but not all) accounts, Prince William Sound has recovered by now from the effects of the Exxon Valdez spill, after some 20 years.
What's in store for the Gulf of Mexico? There have already been pronouncements that the biological systems in the Gulf "will never be the same," Determining whether or not this is true will require an operational definition of "the same"--one that is linked to clear biological mechanisms and ecologically significant consequences, and that acknowledges that a failure to be "the same" may be due to causes other than oil.
Of course, my perspective on these oil spills is that of a scientist. But oil spills have impacts that extend well beyond wildlife and the environment. The Exxon Valdez spill changed the way of life for many people in coastal Alaska. The social and economic impacts of the Deepwater Horizon blowout in Gulf coastal states are already profound and will worsen before they get better. Public attitudes are also affected. The blowout of a drilling platform off of Santa Barbara, California, in 1969, for example, mobilized support for important environmental legislation and led to a Congressional moratorium on offshore oil leasing in many areas that lasted for 27 years. Whether one believes that offshore drilling is a recipe for more disasters or an essential ingredient for economic growth, the legacies of such events complicate efforts to develop a comprehensive energy policy, one that can foster the development of alternative "green" energy sources. The mantra of "drill, baby, drill" no longer resonates with as many people.
Neither the Exxon Valdez spill nor the Deepwater Horizon blowout was anticipated. Such "rare events," however, are becoming less rare. Eight months before the Deepwater Horizon explosion, the Montara well platform in the Timor Sea blew out, creating Australia's largest oil spill. In its exploration proposal for the Deepwater Horizon, BP assured itself, its shareholders, politicians, regulators (who, it turns out, were not regulating) and the public that the risks of deepwater drilling were too small to be of concern. The risks may indeed have been small, but they obviously weren't zero, and we, and the environment, are suffering the consequences.
Who is to blame for the Deepwater Horizon blowout? In a sense, all of us are. Until we find alternative ways to quench our thirst for energy or learn how to live on less energy, the risks of accidents associated with the exploration, extraction, and transport of fossil fuels will grow, and the economic, social, and environmental costs of accidents will escalate.
The overriding message of Deepwater Horizon, and before that of the Exxon Valdez and a litany of other oil spills, is that we must wean ourselves from fossil fuels sooner rather than later. Until that happens, however, we need to develop comprehensive ways of assessing and balancing all the benefits, costs, and risks of oil and of alternative energy sources. We should know where our dependence on oil is leading us.