ON THE PORCUPINE RIVER TUNDRA, Yukon Territory — Here on the endlessly rolling and tussocky terrain of northwest Canada, where man has hunted caribou since the Stone Age, the vast antlered herds are fast growing thin. And it’s not just here.
Across the tundra 1,000 miles to the east, Canada’s Beverly herd, numbering more than 200,000 a decade ago, can barely be found today.
Halfway around the world in Siberia, the biggest aggregation of these migratory animals has shrunk by hundreds of thousands in a few years.
Biologists believe the insidious impact of climate change, its tipping of natural balances and disruption of feeding habits, is decimating a species that has long numbered in the millions and supported human life in Earth’s most unforgiving climate.
Many herds have lost more than half their number from the maximums of recent decades, a global survey finds. They “hover on the precipice of a major decline,” it says.
The “People of the Caribou,” the native Gwich’in of the Yukon and Alaska, were among the first to sense trouble, in the late 1990s, as their Porcupine herd dwindled from 178,000 in 1989 to an estimated 100,000 now.
“They used to come through by the hundreds,” James Firth, 56, of the Gwich’in Renewable Resources Board said as he guided journalists across the tundra.
The global survey by researchers at the University of Alberta, published in the journal Global Change Biology, has deepened concerns about the caribou’s future.
Drawing on scores of other studies, government databases, wildlife-management boards and other sources, the biologists found that 34 of 43 herds being monitored worldwide are in decline.
Liv Solveig Vors, the report’s lead author, summarized what is believed behind the caribou crash: “Climate change is changing the way they’re interacting with their food, directly and indirectly.”
Global warming has boosted temperatures in the Arctic twice as much as elsewhere, and Canadian researchers say the natural balance is suffering:
• Unusual freezing rains in autumn are locking lichen, the caribou’s winter forage, under impenetrable ice sheets.
• Mosquitoes, flies and insect parasites have always tormented and weakened caribou, but warmer temperatures have aggravated this summertime problem, driving the animals on crazed, debilitating runs to escape and keeping them from foraging and fattening up for winter.
• The springtime Arctic “green-up” is occurring two weeks or more earlier. The caribou migrations evolved over ages to catch the shrubs on the calving grounds at their freshest and most nutritious. But pregnant, migrating cows may now be arriving too late.
Vors said caribou are unlikely to adjust.
“Evolutionary changes tend to take place over longer time scales than the time scale of climate change at the moment,” she said.
Climatologists foresee northern temperatures rising several degrees more this century unless global greenhouse-gas emissions are sharply reduced soon.
Caribou herds have gone through boom-and- bust cycles historically but were never known to decline so uniformly worldwide.
