Loss of Arctic Ice Makes Polar Bears Vulnerable to Extinction
By Katherine Hopwood
Polar bears are one of the most prominent faces of climate change awareness, but not many people understand the true implications that melting sea ice could have on the species, especially on future generations of bears. A recent study by Regehr et al. (2016) found that by the year 2050, the world’s entire population of polar bears could be reduced by anywhere from 30% up to 80% due to extensive habitat destruction and loss of food opportunities caused by the melting ice in the Arctic Circle.
A Changing World
As levels of human-produced carbon dioxide rise, Earth’s climate is being artificially altered in a phenomenon termed anthropogenic (human-caused) climate change. This leads to increased worldwide temperatures and the melting of polar ice caps, as well as many other undesirable impacts. Melting sea ice has a particularly negative effect on polar bears, as it is their prime habitat and they rely on it for food and shelter. The true extent of this damage is still unknown, as emissions being produced today will impact future climate measures, but with current predictions, the Arctic ice cap will continue to shrink well into the future, and polar bear populations will fall with it. The likely inevitable loss of polar bears could be even greater than predicted, since melting ice will trigger cascading losses due to numerous tipping points resulting from receding ice that will only compound the issue.
How Do We Know?
Loss of Arctic ice is fairly well recorded, but its link to polar bear abundance is not. To make a reasonable estimate of the impact of its loss on polar bears in the future, a group of scientists used three different approaches to make future population estimates (Regehr et al 2016). These were based on measurements of past losses of ice in distinct regions of polar bear habitat and how the local bear population had changed relative to the surface area of ice available in those separate areas over a period of thirty years.
The authors of the study then applied those observations to the aforementioned three approaches to making well-founded projections for future sea ice loss in order to be able to model the future regional population decline for each successive generation, with an estimated value of about 35–41 years for three generations. They then compared those losses to the categories laid out by the IUCN Red List, which provides measures for extinction threat on the species and subspecies level.
Using the methods outlined above, the authors of the study found that over the three generations projected, the dire predicted decline of numbers of polar bears qualifies the species to be classified as vulnerable to extinction based on the IUCN Red List specifications. Despite the sensitivity of the short-term predictions to future events, meaning small changes could have large impacts on real future effects on polar bears and sea ice, it is fairly clear that polar bear numbers will suffer a significant decline in the years to come — and humans are almost certainly to blame.
What Does It All Mean (And Why Do We Care)?
Listing polar bears as vulnerable to extinction due to climate change could lead to legislative protections for the species, as well as bringing the issue of the human-caused threats to polar bears to the attention of the world on a more urgent scale. It could also inform conservation movements interested in the protection and well-being of the animals, as well as highlight a greater need to take responsibility for human impacts on the planet and reduce emissions of carbon dioxide and other greenhouse gases within a fairly limited time frame. By extension, taking such steps to protect the polar bears means protecting humans as well, since sea level rise due to melting ice caps directly threatens coastal and island settlements, not to mention the many other unpleasant health and environmental detriments known to be caused by climate change, so it is doubly important and self-beneficial to fight for the protection of polar bears in the uncertain years to come. Additionally, future studies of polar bear populations are important, as they will allow us to see how accurately the projections of this singular study line up with the actual reductions in numbers, to better inform policy decisions and management for the species. Such studies could also incorporate a different set of models to factor in differences in approaches to population measurement to provide a broader view of this vital issue.
Regehr, Eric V., et al. “Conservation status of polar bears (Ursus maritimus) in relation to projected sea-ice declines.” Biology Letters, vol. 12, no. 12, 7 Dec. 2016, p. 20160556., doi:10.1098/rsbl.2016.0556
