The tiny buffaloberry has been the primary source of food for Alberta’s largest mammal, the grizzly bear, for millennia. But according to research by University of Calgary geographer Greg McDermid, the Earth's increasing temperatures will ripen the berries early, threatening the important meal for the bears.
A polar bear on a shrinking sheet of ice has long been the symbol of climate change. McDermid hopes his research will help Albertans understand climate change is as much a local issue as it is a global one.
“The Arctic is like a precursor of what we’re going to be seeing later on further south,” says McDermid. “It’s not just polar bears and ringed seals and caribou, but things here in our ecosystem too.”
The buffaloberry is the most abundant fruiting shrub in the grizzly bear habitat, and with no salmon in Alberta, it is also the bears’ most important food source. Scientists have documented individual bears in Alberta eating up to 200,000 berries per day.
McDermid says bears spend their entire waking year nose to the ground, sniffing from one seasonal food to another, preparing for hibernation.
Near the end of summer, when the buffaloberries are in season, the bears’ feast on the tart red fruit, marking their most significant caloric intake of the year.
“Essentially, how much weight they put on during buffaloberry season will determine a lot of things,” McDermid says. “Do they have enough fat to last the winter? Will the females be able to have cubs?”
McDermid’s research is based on a concept familiar to gardeners: plant development is tied very closely to temperature accumulation. When there is a hot summer, plants develop quickly and harvest is early.
“If you take a tomato and put it into a greenhouse, it develops twice as fast because it’s warm in the greenhouse,” McDermid says.
Because climate change means warming temperatures, McDermid realized the principle of temperature accumulation could be applied more broadly: from a single plant to an entire landscape.
Based on this, McDermid's PhD student, David Laskin, discovered how to track temperature accumulation in plants with satellite remote sensing, a technique that collects data from the energy that is reflected from Earth. They found this method predicts the stages of the buffaloberries extraordinarily well.
They then applied a formula to predict future development of the berry under warming temperatures.
The results showed that by the year 2080, buffaloberries in the Rockies will ripen nearly three weeks earlier than they currently do.
“So the bears will have to last three weeks longer before they hibernate. That changes things,” says McDermid.
He likens it to getting a paycheque three weeks late but still having bills to pay. Similar to someone altering their lifestyle to meet penny-pinching circumstances, the bears will need to change their behaviour. This likely will mean travelling to new places, he says.
Spotting both grizzly and black bears in communities once the buffaloberry season is over is not unusual. The decorative shrubs and bird feeders in people’s yards provide an alternative food source for the bears when times are lean. An early buffaloberry season may cause an increase in this behaviour, McDermid says.
Bears that have stored sufficient body fat will have more cubs and lactate longer. But the prolonged gap between the bears prime feeding period and hibernation could negatively affect the reproductive rates of the already threatened grizzly bear.
The grizzly bear population has gone down approximately 30 per cent, from 1,000 bears in 2002 to 691 in 2010, according to the most recent report from the Alberta government.
Grizzly bears’ will not be the only species affected by the changing buffaloberry schedule.
“Food webs are complicated. If you change one thing, it reverberates throughout the food web in ways that are difficult to predict,” says McDermid. “It’s going to go beyond grizzly bears.”
Other “less-heralded species” will be affected, as well, but McDermid believes grizzly bears’ will catch Albertans’ attention.
“The grizzly bear is a symbol of our Western wilderness,” he says. “If something as big and powerful as the grizzly bear can be a victim of climate change, it stands as an example.”
- By Kate Mackenzie