Penguin Decline Due to Global Warming?

John Roach
for National Geographic News
September 13, 2004

The Earth is getting warmer, according to most scientists. In recent years that phenomenon has prompted researchers to investigate what effect rising temperatures are having on cold-loving penguins and other wildlife species.

Les Underhill directs the Avian Demography Unit at the University of Cape Town in South Africa. He suspects that global climate change may be responsible for declining penguin populations on South Africa's Prince Edward Islands.

The islands dot the Indian Ocean some 1,000 miles (1,770 kilometers) off the South African coast.

Most of the islands' penguin colonies are dwindling. According to Underhill, one reason for the decline may be a climate-induced southward shifting of food-rich waters. The change may have forced the seabirds to swim farther to forage.

Underhill and his colleagues will soon begin to test this idea. The researchers plan to place electronic tracking devices on the islands' penguins to record when they go out to sea to get food for their chicks and when they return.

"We suspect that one of the consequences of global climate change is that, with warmer seas, the journeys will become longer," he said in an interview with the radio program Pulse of the Planet.

Food-Rich Waters

The Prince Edward Islands sit near the southern boundary of the Antarctic Circumpolar Current (ACC). It is in these food-rich waters that the islands' penguins are thought to forage.

Considered the greatest of all ocean currents, the Antarctic Circumpolar Current mixes waters from the Indian, Pacific, and Atlantic Oceans. It swirls about 140 million cubic meters (4.9 billion cubic feet) of water per second around Antarctica.

The southern edge of the current is marked by a boundary separating it from the cold coastal waters along the Antarctic continental shelf. Waters to the north of the boundary are several degrees Celsius warmer than those to the south.

"The southern boundary of the ACC is noted for being a food source," said Eileen Hofmann, an oceanographer at Old Dominion University in Norfolk, Virginia.

Continued on Next Page >>


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