A Whale of a Decline
How whaling wrecked an Alaskan ocean habitat
Roger Di Silvestro
THE DECIMATION of kelp forest ecosystems off southwest Alaska, which affects myriad species including commercially valued fish, may be traced to the destruction of whale populations in the area more than 50 years ago, according to research published recently in the Proceedings of the National Academy of Sciences. “The message is that overfishing and massive extraction can lead to food-web impacts that are unexpected and unintended,” says Alan Springer of the University of Fairbanks, the lead of eight coauthors.
Here’s the chain of evidence: Half a century ago, orcas off Alaska were feeding happily on baleen and sperm whales. After World War II, however, the orcas faced increasing competition from whaling vessels. As hundreds of thousands of whales were removed from the North Pacific from 1946 to 1979, the ocras were forced to hunt other species. They turned to harbor seals (the most nutritious of local pinnipeds), which collapsed beginning in the early 1970s; then to fur seals, which collapsed beginning in the mid-1970s; followed by sea lions, which began to drop in the late 1970s; and finally to sea otters, which started to decline in the 1990s. With the otters reduced, their natural prey—sea urchins—began to increase. The urchins in turn ate up the kelp. “It’s staggering that it occurred over such a large area in such a short time—just a few years,” says Jim Estes, one of the coauthors. “The food-web interconnectivity—that urchin explosions could be linked to whaling 50 years ago—is amazing.”