Polar Bears and Ringed Seals: Rising global temperatures affect Arctic ecology

Carson Clark

            Warming atmospheric temperatures are poised to shift ecological makeups around the world but changing conditions will impact organisms and locations at different rates. The Arctic is among the locations expected to see the most dramatic and rapid ecological changes. Researchers Cosmo and Hall (2014) have already shown that Arctic temperatures are rising at a rate three times that of average global warming.

            The rapidly shifting temperatures pose a threat to the future and stability of many Arctic organisms. Of particular interest to ecological researcher Charmain Hamilton and her team are the changing interactions between predatorial polar bears and their ice-dwelling prey, the ringed seal.

            Arctic polar bears primarily hunt ringed seal by stalking seals that are “hauled” out on sea-ice or by still-hunting at seal breathing holes in the ice. The longevity of these methods are endangered by the rising temperatures and diminishing Arctic sea-ice. Hamilton and colleagues intend to explore the ecological and behavioral consequences of these rising Arctic temperatures.

           Hamilton and her team captured and tagged a total of 60 seals across two studies--one done in 2002-2004 and the other in 2010-2012--to monitor behavioral changes in polar bears. The researchers were primarily looking at the distance the polar bears in each group moved per day. They wondered whether the reduction in the amount of sea-ice over the time period would correlate with greater distances polar bears would have to move in order to find sufficient food.

“Sea-ice declines in Svalbard have altered the behavior of polar bears”

Fig 1 shows polar bears traveling significantly further each day in the summer months after the 8 year period.

        The results of the study provide convincing evidence for this proposed relationship. As shown in Figure 1 above, the daily distances the polar bears traveled in the summer rose significantly during the 8 year period. This reduction of sea-ice has shown rapid implications to Arctic ecology. Figure 2 below is a graphical representation of the locations of the tagged polar bears during the study. The GPS results are consistent with the notion that polar bears had to travel to different regions of the archipelago to obtain enough food.

Fig 2 GPS data shows that polar bears are moving to new, more northern locations on the archipelago.

      These metrics offer compelling evidence for the fact that warming Arctic temperatures are causing changes in predator-prey systems and organism behavior. In addition to the increasing travel distances, Hamilton and her team also found evidence that polar bears were spending more time near ground-nesting birds, whose eggs have been known to be a secondary food source of the apex Arctic predator. This underscores the interconnectedness of Arctic ecology; reductions in sea-ice have single-handedly reduced the amount of time ringed seal haul on the ice, which in turn forced polar bears to travel further distances for their daily quota of food, as well as encouraged polar bear predation of ground-nesting birds.

      In a broader light, this study displays the dramatic ecological impacts of rising global temperatures. Though the Arctic ecosystem may seem far-removed to many, the rates of ecological disruption will only quicken, and the geographical range of effect will only grow. Further research could offer fresh insight and evidence for the breadth of change our global ecosystem and biosphere could soon undergo.

Sources

Hamilton, Charmain D., et al. "An Arctic predator‐prey system in flux: climate change impacts on coastal space use by polar bears and ringed seals." Journal of Animal Ecology (2017).

Comiso, Josefino C., and Dorothy K. Hall. "Climate trends in the Arctic as observed from space." Wiley Interdisciplinary Reviews: Climate Change 5.3 (2014): 389-409.