The Heat Is Online

Collapse of Subarctic Ecosystem Linked to Ocean Warming

Aleutian Islands: A Wilderness Ecosystem in Collapse

Scientists investigate a stunningly swift and extreme transformation

The Philadelphia Inquirer, Jan. 28, 2001

KADAK ISLAND, Alaska - There are few places on Earth that have changed so much and sofast as the narrow arc of islands where the Pacific Ocean greets the Bering Sea.

The Aleutian Islands are in the middle of nowhere. No tourists, no cruise ships, no charteredfishing trips, no quaint country inns. On a quiet day, when the turbulent seas and legendary winds are still, you can hear a killer whale breathe.

But look and listen more closely. Something is missing.

Where are the sea lions, fat and happy, napping on the rocks and barking at their pups? And the furry sea otters crunching on urchins? What became of the ample king crab andshrimp, and the schools of silvery smelt?

And where are the lush, undersea forests of kelp that provided food and refuge for fish?

As sudden and savage as an Arctic storm, some mysterious phenomenon has transformedthis spectacular 1,300-mile archipelago in just a handful of years.

A vast subarctic ecosystem is collapsing, and no one knows why.

The sudden changes in the Gulf of Alaska and the Bering Sea have inspired an eclectic team of men and women to try to solve an extraordinary environmental whodunit. Virtually alone in a forbidding wilderness closer to Siberia than to Anchorage, they have been dive-bombed by eagles, bitten by otters, buffeted by 70 m.p.h. winds, rattled by earthquakes, and lost in storms.

And each year, they return for more, drawn back by the Aleutian paradox. If this rugged, remote ecosystem is collapsing, can any place on Earth be safe?

Jim Estes, a marine ecologist at the U.S. Geological Survey in Santa Cruz, Calif., has traveled to the Aleutians for 30 summers, studying what once was the world's largest and healthiest population of sea otters. Three summers ago, Estes realized the otters had virtually disappeared while he watched.

There were no bodies to dissect, few clues to decipher. The otters are not starving. They are not sick. They have simply vanished.

Throughout the Gulf of Alaska and probably the Bering Sea, too, the balance of prey and predator has been upended, a transformation so extreme that it's being called a "regime shift." Waters once brimming with seals, otters and king crab are now dominated by sharks, pollock and urchins. Virtually no creature remains untouched.

Piece by piece, over the last three years, scientists have started to solve the puzzle. Clues point toward something - almost imperceptible - that happened in the ocean in 1977. But the answers are more disturbing than satisfying, more elusive than conclusive. It seems the ocean's chain of life is actually a fragile, silken web. If just one strand is removed, the whole thing unravels. And it may never be whole again.

In the 1980s, as many as 100,000 otters inhabited the islands. Today, only about 6,000 remain, according to aerial surveys. Between 1992 and 2000, the population dropped by 70 percent, a rate of decline that researchers say is unprecedented for any mammal population in the world.

In 1995, when they began to notice the signs of a population decline, marine biologist Tim Tinker and Estes, who specialize in otter behavior and population biology, at first looked for signs of disease, famine or reproductive troubles. They found none.

For a couple of years, as the decline steepened, they were baffled. If thousands of otters had died, where were the bodies? Then it dawned on Tinker: Perhaps the animals were being eaten.

By killer whales.

Otters are so small and killer whales so voracious that four whales could have eaten 40,000 otters in five years.

But orcas had lived in harmony with otters for thousands of years on the Aleutians. Why, all of a sudden, were they preying on them?

To find the answer, biologists simply had to follow the food chain.

Orcas customarily feed on sea lions and seals, which are packed with high-calorie blubber. But the population of Steller sea lions, the world's biggest sea lions, took a sharp dive in the late 1980s. Harbor seals also declined at a similar rate.

By 1992, otters were the only plentiful marine mammals left in Aleutian waters. The orcas, in their hunt for calories, apparently had been forced to switch prey.

The effects cascaded rapidly down the food chain.

With far fewer otters around to eat them, sea-urchin populations exploded, increasing eightfold within a few years. As many as 100 of the spiny green creatures now cover each square foot of ocean floor around the Aleutians.

The urchins, in turn, ate the kelp.

When the leafy undersea forests vanished, so did many of the rockfish, snails, starfish, and other creatures that use the kelp for food, shelter and breeding grounds. Some local seabirds, mainly puffins and kittiwakes, also are hurting from the lack of fish.

The Aleutians offer proof that one small ecological change can move like a tsunami throughout the entire ocean realm.

Yet the snarl in the food web had to begin somewhere. Where, scientists wondered. And, even more important, who - or what - did it?

Scientists are exploring many factors - global warming, overfishing, pollution - that might have played a role in the Aleutians' misfortunes. Looking back, they theorize that the key event may have come in 1977, when a sudden warming - just two degrees Celsius - in the average temperature of the Gulf of Alaska was recorded.

While they cannot know for sure, researchers believe the chain of events likely happened like this:

Warmer water caused plankton - short-lived and ultrasensitive to temperature changes – to disappear. Tiny copepod and krill probably followed quickly.

The shrimp and crab, along with smelt fishes such as capelin and herring, would have vanished afterward, deprived of their food, to be replaced by an explosion of cod and pollock.

By the mid-1980s, the problems spread to young mammals.

The decline of smelt probably triggered the collapse of the seal and sea-lion populations,say marine mammal biologists, including Kathy Frost of the Alaska Department of Fish and Game. The smelt are high in fat, and without them, baby mammals might not find enough calories to survive the winters.

But salmon like warmer water. Their populations have increased, drawing sharks, which feed on salmon and, at times, on seals and sea lions.

All of a sudden, the Aleutians had turned into a predator pit, unsafe for marine mammals.

Copyright 2001 Los Angeles Times