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MOST seabird populations hit by the Exxon Valdez oil spill in Alaska have
still to show signs of recovery over a decade after the disaster, say scientists
from the US Fish and Wildlife Service.

Their findings flatly contradict the claims of both Exxon, the oil company
responsible for the spill, and other researchers who say that all affected
species are well on the road to recovery, if not back to normal.

David Irons and colleagues in Anchorage surveyed seabird populations over
eight years in Prince William Sound, scene of the 1989 spill. Of 17 taxa whose
numbers were hit by the spill, he found that four showed only a “weak to very
weak” recovery from the disaster. Nine “showed no evidence of recovery”, while
four continued to show signs of being increasingly affected by the pollution
from the spill.

Seabirds that don’t seem to be recovering include cormorants, various gulls,
grebes, terns and murres, a kind of guillemot hardest hit by the spill. Most of
the 30,000 oil-covered carcasses collected in the months after the spill were
murres. “Densities of pigeon guillemots in oiled areas are still going down in
summer,” says Irons.

However, Exxon, now part of ExxonMobil, which has been involved in lengthy
litigation since the disaster, says that “the environment in Prince William
Sound is healthy, robust and thriving”. Its claims are backed in part by the
findings of John Wiens of the University of Colorado, another leading analyst of
the spill’s aftermath. He has recently concluded that “all of the impacted
species show strong evidence of recovery”.

Wiens has said that “preconceptions that oil spills are bad can easily lead
to one adopting an advocacy position in which science suffers”. But Irons
disputes Wiens’s methodology. He says Wiens uses a relatively tough test for
showing birds have suffered after the spill, and a less demanding standard for
identifying recovery. “The burden of proof is placed on the data to establish
injury, but not recovery,” he says.

Irons believes that birds are still suffering because food in the intertidal
zone and shallow waters near the shore, such as mussels, is still contaminated
with oil. Populations of other prey species are still much lower than before the
spill, Irons says. For instance, Pacific herring and clams “had not recovered by
2000″.

ExxonMobil argues that it is unreasonable to expect all bird populations to
recover because there are other environmental changes affecting the numbers.
“For example, average summer water temperatures have increased in the last 10
years at least three to four degrees above the historical average,” says the
company.

But Irons believes the oil spill is still to blame. “Lingering effects of the
spill and natural variability appear to be acting in concert in delaying
recovery of the bird populations,” he says.