Skating on thin ice: polar bears in a warming future
On International Polar Bear Day, the plight of these apex predators could not be more evident, as a result of a myriad of threats to their existence due to climate change.
As their name suggests, polar bears live in the Arctic polar regions of Canada, Greenland, Russia and Alaska. Kristin Laidre, a UW scientist at SAFS, shares that polar bears require ice for almost every aspect of their existence, including feeding, moving, breeding and in some places, maternity denning.
Why is International Polar Bear Day celebrated on February 27th? Because it’s the time mothers and cubs are denning across the Arctic and highlights just one of the existential threats posed by a warming climate at a particularly vulnerable time in a polar bear’s life.
Studying ecology and population dynamics of Arctic marine mammals, Laidre uses data on individual movements, foraging behavior, and life history to unite behavioral, population, and evolutionary ecology. In this time of global climate change, her research on the impacts of a warming world on ice-dependent species is of particular interest.
The conditions of a polar bear’s body are heavily impacted by the loss of ice according to Laidre. With not enough time to feed and gain the fat resources needed to survive the year, the loss of sea ice causes a cascade of issues including on reproduction, survival, and population abundance.
But is there hope for the future? Can polar bears adapt to a warming climate? Across the polar regions, Laidre says that the type of sea ice, the rate we are losing sea ice, and the productivity of the ecosystem is resulting in a variability of response of the world’s 19 polar bear populations.
However, this regional difference is underpinned by a clear prediction: a 30% reduction in the global abundance of polar bears is forecast over the next several decades if greenhouse gas emissions are not reduced.
So what inspires a new generation of scientists to get involved in polar bear research? Sarah Teman, a MS student at SAFS working in Kristin Laidre’s lab, became interested in studying polar bears due to their unique physiology and life history, and the fact that they face very challenging threats.
In her thesis project, conducted under the ‘One Health’ concept that the health of wildlife, ecosystems, and humans are deeply connected, she aims to measure the health of polar bears in the southern Beaufort Sea over time.
Understanding the health of these apex predators is not only important from a wildlife or ecosystem health perspective, but also for Indigenous communities around the Arctic who rely on bears as an important food and cultural resource.
Meanwhile, PhD student Jenny Stern, also working with Laidre, was drawn to the field due to the extreme nature of the Arctic ecosystem and is exploring what is required for top predators to survive in a rapidly changing climate.
Focusing on the Baffin Bay polar bear subpopulation, Jenny’s dissertation looks at feeding ecology and asks some important questions such as how diet varies among demographic groups and space-use strategies.
Jenny analyzes hair and fat samples collected from captured polar bears using stable isotopes and fatty acid analyses and combines this data with movement data from adult females tracked with satellite collars.
When asked about a memorable field experience, she shared that during a 40-day Arctic Research Expedition on a US Coast Guard icebreaker, she got to see a polar bear approach and stand on its hind legs whilst the ship was stuck for a few days in an ice floe. Watching her subject of research exploring and moving through its environment was a favorite memory of hers.
Research remains a critical frontier in efforts to combat the negative impacts of global climate change on species and environments around the world, and the research underway at SAFS highlights just some of the scientific work involved in that effort.