Analysis of older data revealed that NAO-related changes in seasonal ice cover may have contributed to major declines in seal populations on the east coast of Canada from 1950 to 1972 and to a period of steady recovery from 1973 to 2000.
"This clearly shows that harp seal populations across the Atlantic fluctuate pretty much in synch with NAO trends and associated winter ice conditions," Johnston said. "But there's a caveat: regardless of NAO conditions, our models show that sea ice cover in all harp seal breeding regions in the North Atlantic have been declining by as much as 6 percent a decade over the study period. The losses in bad years outweigh the gains in good years."
A key unanswered question, he added, is whether seals will be able to respond to the long-term trend by moving to other, more stable ice habitats.
Recent reports that some harp seals are whelping in new breeding grounds off East Greenland indicate some shifting may be taking place, but thousands still return each year to traditional breeding grounds in the Gulf of St. Lawrence or along the Front, off Newfoundland, regardless of ice conditions.
"There's only so much ice out there, and declines in the quantity and quality of it across the region, coupled with the earlier arrival of spring ice breakup, is literally leaving these populations on thin ice," Johnston said. "It may take years of good ice and steady population gains to make up for the heavy losses sustained during the recent string of bad ice years in eastern Canada."
|Contact: Tim Lucas|