Why are polar bear populations declining?
It is not new information that climate change is having a negative impact on polar bear populations, but what is the reason behind their decreasing numbers?
Polar bears rely on sea ice to hunt and catch seals, which is their main source of prey for survival in the harsh Arctic environment. Global temperatures are expected to increase by as much as 16 degrees by 2100, as long as we continue to emit the same volume of emissions into the atmosphere as we are today (Romm, 2011). The current and increasingly longer ice-free periods in the polar regions, force polar bears ashore where they remain reliant on their body-fat reserves and lactation for survival of themselves and their cubs(Molnár et al., 2020). Therefore, if sea ice were to be removed completely from the planet, polar bears would lose both their best option for hunting prey as well as their homes! We all know that everything that lives must obtain food in some way or another, meaning polar bears relying on their body energy reserves as their primary source for survival will not last long, resulting in the inability to raise cubs due to the lack of lactation for their young, leading to an inevitable downward trajectory of polar bear populations eventually leading into the extinction of this beautiful species.
What evidence suggests that polar bears could become extinct?
With Arctic sea ice receding at a rate of 13.3% per decade since 1979 (Serreze and Stroeve, 2015), simulations such as the Geophysical Fluid Dynamics Laboratory Coupled Physical Model of the Canadian Arctic Archipelago (CAA) can predict the lengthening periods of ice-free regions and decreasing sea ice thickness in the 21st Century (Hamilton et al., 2014). With lengthening ice-free regions, periods of starvation for polar bears would likely increase since their platform for catching seals is disappearing. Without enough body mass to support their energy and metabolic needs, this data also supports the increased likelihood of reproductive failure.
Now, you might be thinking, polar bears are already being forced to hunt on land, could they not just obtain other sources of food this way? Yes, it is true that polar bears have been witnessed stealing eggs from bird nests, berries, sea birds, rodents and just about any other types of food that they can get, but the equivalence to the energy obtained from one adult ringed seal is next to impossible to achieve. This would be equivalent to approximately 1.5 caribou (Rangifer tarandus), 37 Arctic char (Salvelinus alpinus), 74 snow geese (Anser caerulescens) and 216 snow goose eggs (Pagano and Williams, 2021)! Therefore, without ice to catch seals, polar bears will be unable to survive on such small amounts of energy.
What can we do to help save the polar bears?
In order to slow the rate of the global warming, global increase in temperatures, every single one of us has the potential to can make a huge impact! We have all heard that turning the lights and running water off when not in use are ways to help the changing climate, but what else can we do to help? Here are the top 3 things that you can do to help save our planet and in turn, save the polar bears:
1 = Reduce your meat consumption
Romm, J., 2011. Science stunner: On our current emissions path, CO2 levels in 2100 will hit levels last seen when the Earth was 29°F (16°C) hotter. [online] Thinkprogress.org. Available at: <https://thinkprogress.org/science-stunner-on-our-current-emissions-path-co2-levels-in-2100-will-hit-levels-last-seen-when-the-494580182716/> [Accessed 20 May 2021].
Stirling, I., Andrew, D., 1993. Possible Impacts of Climatic Warming on Polar Bears. Arctic, 46(3), pp. 240–245.
Molnár, P., Bitz, C., Holland, M., Kay, J., Penk, S. and Amstrup, S., 2020. Fasting season length sets temporal limits for global polar bear persistence. Nature Climate Change, 10(8), pp. 732-738.
Serreze, M. and Stroeve, J., 2015. Arctic sea ice trends, variability and implications for seasonal ice forecasting. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 373(2045).
Hamilton, S., Castro de la Guardia, L., Derocher, A., Sahanatien, V., Tremblay, B. and Huard, D., 2014. Projected Polar Bear Sea Ice Habitat in the Canadian Arctic Archipelago. PLoS ONE, 9(11).
Pagano, A. and Williams, T., 2021. Physiological consequences of Arctic sea ice loss on large marine carnivores: unique responses by polar bears and narwhals. Journal of Experimental Biology, 224(Suppl_1).