Warming May Be Hurting Gray Whales' Recovery
By Juliet Eilperin
Washington Post Staff Writer
Tuesday, September 11, 2007; A12
As many as 118,000 gray whales roamed the Pacific before humans
decimated the population through hunting, and human-induced climate
change may now be depriving those that remain of the food they need,
according to a study released yesterday.
The research, based on a detailed analysis of DNA taken from gray
whales living in the eastern Pacific, highlights how human behavior
has transformed the oceans, the scientists said.
Today there are only about 22,000 Pacific gray whales, including
about 100 in the western Pacific. By examining the genetic
variability of the current population, scientists at Stanford
University and the University of Washington at Seattle calculated
that there were between 76,000 and 118,000 gray whales in the Pacific
before commercial whaling in the 1800s shrank their numbers.
Federal officials took eastern Pacific gray whales off the endangered
species list in the mid-1990s, but a rise in sea temperatures appears
to have limited the whales' available food. A recent spike in deaths
among gray whales may suggest "this decline was due to shifting
climatic conditions on Arctic feeding grounds," the researchers wrote
in the paper, being published online this week in the Proceedings of
the National Academy of Sciences.
"There definitely are large-scale ecosystem effects going on," said
Stanford doctoral student S. Elizabeth Alter, the lead author, in an
interview yesterday.
"One of the most exciting things" about DNA analysis, she said, is
that it gives us "the opportunity to look back in time and see what
the ocean looked like before human impact."
The decline in gray whales has affected the ocean in a variety of
ways, according to the researchers. Because the animals feed on the
ocean bottom by sucking in and expelling sediment that contains
shrimplike creatures called amphipods, the scientists wrote, historic
populations may have redistributed enough sediment to feed a million
seabirds.
Aboriginal tribes are currently allowed to kill as many as 125
eastern Pacific gray whales a year under International Whaling
Commission rules, though this practice has sparked controversy. In
light of the new data suggesting that the whales' numbers were more
depleted than was previously known, international officials need to
reconsider the amount of gray whale hunting they currently allow, the
researchers said.
On Saturday, five members of Washington's Makah tribe shot and killed
a gray whale without the required permit. Coast Guard officials
caught the men and turned them over to tribal police. On Sunday,
tribal council leaders issued a statement denouncing the men's
actions and vowed to prosecute them.
Stephen R. Palumbi, a professor of marine sciences at Stanford and a
co-author of the study, said the research suggests that given the
right conditions, the number of gray whales could increase in the
years to come. But a warmer Bering Sea could impede this recovery, he
said, because it is killing off some of the food the whales consume.
When emaciated gray whales washed ashore between 1999 and 2001,
scientists initially speculated that the animals were exhausting the
ocean's "carrying capacity," Palumbi added, but it could be instead
that global warming is to blame.
"It's not a conclusion we can come to. It's a hint," he said in an
interview. But if humans are affecting the ocean's "capacity to
support life, it's got to make you worry, it's got to make your wonder."_______________________________________________
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