to a quarter-century of research and monitoring, says a new study, scientists
now know how different wildlife species were injured by the 1989 Exxon Valdez
oil spill and how long it took for populations to recover.
say this information may have important implications when responding to other
oil spills, when conducting damage assessment studies after spills and when
considering the environmental risks associated with extracting and shipping
wildlife species in the spill area vary so much in terms of what they eat,
habitats that they use, and their ability to rebound after a drop in numbers,
researchers saw huge differences in how long it took for populations to
recover,” said Dan Esler, a Research Wildlife Biologist with the U.S.
Geological Survey and lead author of a recently released paper on the subject.
species were barely affected, others such as bald eagles, rebounded quickly,
and other species took much longer to recover, such as sea otters.”
paper reviewing scientific studies of wildlife recovery, entitled “Timelines
and mechanisms of wildlife population recovery following the Exxon Valdez oil
available in the journal Deep Sea Research II, as part of a special issue
focused on sources of ecological variability in the Gulf of Alaska.
addition to differences in the time required for full recovery, USGS and
collaborators from the U.S. Fish and Wildlife Service, Oregon State University,
and the North Gulf Oceanic Society identified ecological factors that affected
the degree of injury:
Species that foraged on invertebrates that occur in or on contaminated
sediments were more likely to be affected by the oil spill than those that fed
on fish or zooplankton in the water column.
Species with low reproductive rates, such as orcas, have limited capacity to
recover; in fact, orcas still have not returned to pre-spill numbers.
Some population changes that were not related to the oil spill; for example,
two species of seabirds, pigeon guillemots and marbled murrelets, may have been
affected by oil exposure, but long-term analyses showed declines in numbers
before and after the spill, probably related primarily to changing ocean
USGS has previously led long-term studies of sea otters and harlequin ducks,
two species that showed lack of recovery for over two decades after the spill.
Research Wildlife Biologist Dan Monson, noted “Sea otters were exposed to
lingering oil in beach sediments long after shorelines appeared clean and oil
exposure affected survival rates and population growth until at least the