During the “polar vortex” that recently swept the US, Chicago’s Lincoln Park Zoo was forced to bring its polar bear indoors as it was “too cold” for a bear acclimated to Chicago’s “normal” winters (where temperatures of -20°C are not uncommon). As if on cue, a chorus of media pundits and politicians sang the end of global warming.
We should all know better of course. Fluctuations in the weather, like the recent shift in the polar vortex that brought Arctic deep-freeze to much of the US, will continue, and even be magnified, as the earth steadily warms. Laws of physics require the world to warm as long as atmospheric greenhouse gas concentrations rise. And while North America experienced deep freeze, much of the rest of the world sweltered under record heat, and the globe’s average temperature continued to rise.
For wild polar bears, the continuing rise of the earth’s temperature is a problem. During 30 years of studying these bears in Alaska, I documented positive and then negative trends in their status.
In the early 1980s I discovered Alaska’s great white bears had recovered from the excessive hunting that ceased in the 1970s. By the middle of the last decade, however, I witnessed dramatic changes in the sea ice, with increasingly obvious negative effects on the bears. As had previously been documented in Canada’s Hudson Bay, we noticed reduced stature and physical condition of some sex and age groups. More importantly, survival rates especially of young bears were declining. Although female bears continued to give birth, more and more of their cubs were starving to death before reaching their first birthday. Clearly, this was a trend that could not be sustained.
In September of 2007, after exhaustive analysis of all of the available data, my colleagues and I predicted that we could lose two thirds of the world’s polar bears by the middle of this century — perhaps all of them by 2100. That prediction led to the listing of polar bears as a Threatened Species under the US Endangered Species Act (ESA) – the first species listed under the ESA due to human-caused global warming.
Polar bears occur in 19 populations spread across the vast Arctic expanse. They will not all respond to a warming world in exactly the same way or at the same time. Some already feel the effects others may not for years. But the near-term variation in effects of warming should not distract us from the ultimate certainty that polar bears will disappear without our help.
According to the fossil record, polar bears have specialised to catch seals from the surface of sea ice for more than 120,000 years. They cannot make a living anywhere else. Nobody claims pandas would suddenly take up eating fish if there is a bamboo failure, or that orangutans will adapt if their old growth forests are converted to coffee and palm oil plantations. Similarly we cannot expect polar bears to suddenly start making a living in an Arctic where the critical habitat is fast fading. Even those bears living in the farthest north reaches of their range will ultimately lose the sea ice habitat on which they depend if the warming is allowed to continue.
In 2010, my colleagues and I published a paper showing that preventing the disappearance of polar bears is all about reducing our use of fossil fuels and halting the rise in global temperatures. We showed there is still time to save polar bears. We can solve this problem, but for each year we delay action, the challenges become more daunting.
Because they depend on a habitat that literally melts as temperatures rise, polar bears are truly an early hallmark of human-caused climate change. The prospect of the polar bear’s demise also is a signal that we need to think differently about this conservation challenge. Past efforts to protect threatened species included “on the ground” measures such as fighting poachers, or building fences around important habitat. We cannot, however, build a fence to protect the ice from rising temperatures.
Polar bear conservation cannot be done in the Arctic. It requires each of us to do what we can to minimise our dependence on fossil fuels. This means walking and biking instead of driving, insulating our homes, and turning the thermostat down in winter and the air-conditioning off in summer. But putting these changes in place, in time, requires policy-level leadership. Society’s reliance on fossil fuels is unsustainable, and is presently maintained only because we are deferring its associated costs to future generations.
Policies that require we pay the true costs of using ancient carbon, such as implementing emissions trading schemes and raising the social cost of carbon, could save the polar bear from extinction. More importantly, it would level the commercial playing field, making renewable energy and other sustainable practices more competitive. The resulting competition, in turn, would create jobs and preserve a climate that will sustain not just polar bears but the rest of us as well. Because without fundamental change the polar bear’s fate, while it may come sooner, will ultimately also be ours.