The polar bear is emblematic of the Canadian wilderness, but as an apex predator, they are also one of the species most at risk from climate change. The Arctic is experiencing the effects of global warming more than any other place on Earth. Temperatures in the Arctic are rising at almost twice the rate of the rest of the world, and this is causing the early break-up of sea ice. Polar bears are dependent on the ice for their survival, which they use as a hunting platform, to secure mates and to travel.
There is a strong correlation between the decline in polar bears and the reduction in sea ice. The loss of sea ice is making it harder for polar bears to find enough seals to meet their dietary requirements. The result is leaner females that are less capable of successfully reproducing and less able to nurture their cubs once they are born.
As explained by the David Suzuki Foundation, the sea ice cover has declined by approximately nine per cent per decade since 1978, and the rate of melting appears to increase each year.
In 2009, polar bear biologists reported that declining sea ice in the Arctic was already harming some populations. At a meeting in Copenhagen, the Polar Bear Specialist Group made the claim that an increasing number of bear populations were in decline. The only population that was known to be doing well was the one in the Canadian high Arctic.
While more than half of the world’s polar bears live in Canada they can also be found in Alaska, Russia, Greenland and Norway. Many of Canada’s bears can be found in western Hudson Bay. In that part of the world ice is breaking up on average seven to eight days earlier with each passing decade. Melting sea ice is forcing the bears ashore where there is little prey for them to hunt. Increased time on land is leading to weight loss, physical deterioration and decreased rates of reproduction.
A recent aerial survey conducted on behalf of the Nunavut government suggests that there are about 1,013 polar bears in Canada’s western Hudson Bay. This number is similar to a 2004 mark-and-recapture or tagging study. Taken together these studies suggest that the number of polar bears is stable.
Andrew Derocher is one of many who do not agree with this assessment. Derocher is Professor of biological sciences at the University of Alberta, he has studied polar bears for 40 years. As he explained in a phone interview with The Star.com, the study actually revealed substantially reduced numbers of cubs and yearlings.
Derocher believes that two to five times more cubs were born in the 1980s through to the 1990s.
In recent years, Derocher and others have documented a decline in body weight of the bears, leading to less cubs being born and a smaller number surviving to adulthood.
“The science of the effects of climate change on polar bears in Hudson Bay is absolutely profound” Derocher said, “the loss of sea ice reduces the body conditions of bears and bears with lower body condition produce fewer cubs and the bears collectively have lower survival rates.”
Being on land where there is no prey, females end up being 30 to 40 kilograms lighter than they were in the early 1980s and they are producing fewer cubs.
“When you put it all together it summarizes a population that is not reproducing sufficiently to maintain the current abundance and that means the population is in decline,” Derocher said. He concludes by saying that the pattern observed in western Hudson Bay is being replicated in other parts of the Arctic.
This summer, in addition to less ice, the polar bears near Hudson Bay had to contend with high heat and even wildfires. As reported by Reuters, these fires encroached on areas where females make their dens.
A polar bear scientist named Steven Amstrup is concerned about the loss of habitat. Amstrup is a former polar bear specialist with the U.S. Geological Survey and now chief scientist at the nonprofit conservation organization, Polar Bears International.
“Not only is the permafrost no longer permanent, tree roots needed to stabilize the den structure are disappearing,” Amstrup said. “The kinds of habitats where mother polar bears in this area give birth to their cubs are simply disappearing as the world warms and [the cubs] survival depends upon the shelter of the den to protect them from the elements.”
As reviewed in another Reuters article, a 2011 study suggests that increasing mortality rates of polar bear cubs is due to the fact that with less ice they are forced to swim long distances. While adult animals can swim vast distances, this study suggests that protracted swims can prove deadly for the cubs.
Starving polar bears may even be cannibalizing each other. Discovery News reported an incident of cannibalism that was captured on film in Hudson Bay in 2009. This was but one of 8 cases alleged to have taken place in the area that year. In 2011, the journal Arctic published another account of cannibalism witnessed by photojournalist Jenny Ross of the Svalbard archipelago last year. Although not unprecedented, polar bear cannibalism is likely to increase as the bears find it increasingly difficult to gain access to their prey.
A 2010 Reuters article reviewed a study which concluded that significant reductions in carbon emissions could cool the planet and rebuild sea ice.
“This is very much scientific evidence that there is hope,” said Amstrup. “If people think that there’s nothing they can do, they will do nothing. Here we’ve demonstrated that we can conserve polar bears.”
Global warming is threatening the entire Arctic ecosystem and jeopardizing the fate of the polar bear. It is not too late to save these majestic creatures, but to do so we must get serious about reducing emissions.