The effects of climate change appear to be driving Arctic fox numbers down in northern Manitoba, threatening their role as “ecosystem engineers” that have a green thumb effect on relatively barren swaths of tundra. That’s according to two separate studies published this summer based on recent research in the Churchill area. “We have classified Arctic foxes as the sort of unique keystone ecosystem engineers in tundra ecosystems because they benefit other plants in the area through their denning activity,” said Sean Johnson-Bice, a PhD candidate at the University of Manitoba (U of M). “These dens are also really important sites likely for other species as well.” In one study, Johnson-Bice and his colleagues spied on Arctic fox dens — from space.
Churchill, about 1,000 kilometres north of Winnipeg, and the neighbouring Wapusk region to the southeast represent the southernmost range of Arctic fox habitat. It’s at these edges where the seasonally snow-white polar predators occasionally decide to dig out dens in otherwise nutrient poor ridges on tundra without much vegetation. Through analyzing high-resolution satellite imagery, the team found they could pick out dens from above. That’s because the dens have a “green up” effect. Over time the once-unproductive tundra ridges undergo a glow up of of sorts, with lush grasses and other vegetation sprouting up all around the dens.
Johnson-Bice said that has to do with what the Arctic foxes are doing, eating and leaving behind around their home. “During the summer they’re bringing all sorts of goose carcasses back and bits of caribou and all that degrading bones and flesh and feathers and stuff … acts as a nutrient sink,” he said. It enriches nutrient poor areas so plants can thrive. Foxes and their cubs are also “pooping and peeing on the dens” and that, too, acts as a fertilizer for local plant growth, said Johnson-Bice. The implication is that the species effectively seeds the area around its den, boosting nutrients and vegetation that in turn provide ecological value to other species. The team found once the foxes colonize a ridge, dens and their associated greenery stick around well after the foxes leave, suggesting the dens bring long-term biodiversity benefits to the area.
