The climate-change clock killing caribou
IN THE WILD, TIMING IS EVERYTHING: MILLIONS OF YEARS OF EVOLUTION have made species dependent on seasonal cues. In parts of North America, fall’s cooler weather signals some birds to fly south and avoid Jack Frost’s chill; meanwhile, shifts in both temperature and sunlight tell maple trees to shed their leaves. As Earth warms, some creatures are rapidly recalibrating their clocks. But others, such as caribou in Greenland, have stuck to the same old timetable. For them, the results are catastrophic.
Arctic caribou herds arrive at their far-north calving grounds in early June, when grasses and sedges would begin to sprout, providing tender, nutritious meals. Caribou, whose internal clocks rely on seasonal changes in light rather than temperature, still arrive at the same time, but global warming has pushed the sprouting schedule up by as much as 26 days. Lately, herds can find only tough-tochew mature plants. The early arrival of Arctic mosquitoes makes things worse. Instead of larva, adult biters now overwhelm and even take down newborns. These climate-induced food and pest problems are killing caribou: In years when one Western Greenland herd meets plants and bugs that emerge early, seven times as many calves die.
Big Biter Arctic mosquitoes can grow to lengths of nearly half an inch.