Mar 1, 2011
Insufficient data mean effect of oil spill cannot be accurately assessed
Scientists are having a difficult time gauging the recovery of marine species from the Deepwater Horizon oil spill in the Gulf of Mexico because they lack sufficient data about historical population size and the distribution, growth rates and reproduction rates of many species.
In a forum paper published in Science, they call for a new research agenda that prioritizes systematic acquisition of baseline data for marine species.
"It is impossible to diagnose whether a species is recovering or floundering if you don't have good data on their status and trends," says Selina Heppell, a fisheries biologist from Oregon State University, US. "Too much of the funding in this country goes toward putting fires out instead of gaining basic biological information, which is what resource managers need to identify and diagnose changes at the population level."
"This is not just about the Gulf of Mexico," Heppell adds. "It is a problem for protected species everywhere."
Heppell, lead author Karen Bjorndal from the University of Florida, US, and eight other authors point to the 1989 Exxon Valdez oil spill in Alaska, where scientists encountered difficulty evaluating the effects on wildlife because of limited data on abundance and demography – the rates of survival, growth and reproduction that are primary indicators of population change.
"Sadly," they wrote, "the situation in the (Gulf of Mexico) is similar more than 20 years later."
The researchers realise that doing an ecological and biological assessment of all marine species would be difficult and expensive. Therefore they recommend the emphasis should be on those species that are the most endangered, or those that have an economic impact, such as those creatures that interact with important fisheries.
"We spend millions of dollars assessing fish stocks," she said. "If we want to monitor endangered species in the same way, we need to focus resources on the aspects of biology that provide the best information about population recovery. That involves research on demography, not just efforts to count individuals."
In their Science article, the authors describe the assessment of sea-turtle populations as a microcosm of the larger issue. In the US, sea-turtle populations are monitored almost exclusively by counting nests on beaches, but when those populations increase or decrease, scientists often don't know why because nesting females are such a tiny fraction of the total population. In contrast, Australian researchers have logged 30 years of demographic data on loggerhead turtles and when a steep decline in their population on the Great Barrier Reef took place in the 1980s and 90s, they were able to attribute it to predation by foxes on nests and incidental capture in trawl fisheries. "Both hazards have now been mitigated by government agencies," the authors wrote, "resulting in an apparently recovering stock."
"We know that hundreds, possibly thousands, of endangered Kemp's Ridley sea turtles were killed or injured by the Gulf spill," says Heppell. "That species had been recovering rapidly – a great conservation success story. What we don't know, and can't determine with the available data, is how detrimental the spill effects will be on that recovery."
Heppell suggests using the money from the resulting fines to develop a new strategy for monitoring and assessment that can identify the specific causes of population decline and make management more efficient.
The authors conclude: "In the wake of the BP oil spill, the need for this policy shift is as clear as it is compelling. If the largest offshore oil spill in US history is not enough to effect this policy shift, what would it take?"