When the topic of climate change is brought up, people usually find themselves thinking of the famous photograph of a polar bear stranded on a block of ice. These bears have become a sort of icon for global warming, and for good reason; even this tough, genetically diverse species cannot persevere when an essential part of their survival is being slowly but surely destroyed.
Background
Global warming refers to the increasing global temperatures due to the greenhouse effect; although this phenomenon is essential to all life on earth, abnormal amounts of greenhouse gasses released from human activities have essentially strengthened this effect to the point where it is harmful. Global warming has hit particularly hard for the Poles; in the Arctic, temperatures are rising about four times faster than the global average, causing sea ice to melt.
Polar bears have relatively high genetic diversity; they have been able to adapt to some environmental changes, including foraging for food on land and swimming more. However, adapting to the loss of sea ice will prove to be a much harder challenge. Sea ice is essential to all polar bears’ survival, including the ability to hunt, mate, and breed.
Hunting
Polar bears get two-thirds of their energy in the late spring and early summer and survive off of that energy in the remaining parts of the year when prey is less abundant. However, as global warming becomes more severe, the sea ice starts to retreat earlier and form later. Although polar bears are strong swimmers, this lengthened period of decreased sea ice causes the bears to catch less prey and swim greater distances; essentially, they obtain less energy but are forced to use more. Polar bears heavily depend on the ice for hunting. Their main prey, seals, are caught by either waiting for them to surface at breathing holes or when they go on the ice to rest. With less sea ice, polar bears have to exhaust much more effort to hunt their prey. Although polar bears can fast for relatively long periods of time, they have a threshold that cannot be crossed; for cubs, this is about 117 days.
Because of this, polar bears have become increasingly dependent on prey other than seals. These include whale carcasses, sea duck eggs, and reindeer. All of these foods are found on land, which shows that polar bears are being forced to adapt to forage more of their food on land.
Breeding
The mating season typically occurs during the months of March to May, causing female polar bears to give birth during the fall. To give birth, these bears dig a den into the snow drift and stay there to mate and care for their cubs for a few months. As temperatures rise, more sea ice and snow melt. Denning periods are very sensitive times, where cubs have a survival rate of 50% or less; decreased thickness of sea snow has made dens prone to collapse. Two-thirds of denning habitats have disappeared since the 1980s.
Humans
Greenhouse gas emissions are the main cause of the polar bears’ downfall; the burning of fossil fuels releases gasses such as carbon dioxide into the atmosphere, which absorb and trap heat close to Earth. This has caused sea ice and snow to melt, destroying an essential part of the bears’ survival. Because of this habitat loss, polar bears are forced to move onto land, therefore, closer to humans. This is where other factors come into play, such as human hunting and oil and gas activities. The Arctic is famous for its large reserves of oil and natural gas; pollution in Arctic waters heavily affects top predators with both bioaccumulation and biomagnification in the bears’ blubber.
Conclusion
These bears’ conservation status is “vulnerable,” because they do not meet the criteria to be formally considered endangered. However, their decline is still very much real; polar bears are losing their only home. According to Dena Cator, former coordinator of the Species Survival Commission, says, “The single most important factor to improve the long-term survival of polar bears is reducing greenhouse gas emissions and stabilizing Arctic sea ice.” A transition into green energy is the path Earth must take to save these animals.
Works Cited
“Global Warming vs. Climate Change | Facts – Climate Change: Vital Signs of the Planet.” NASA Climate Change, https://climate.nasa.gov/global-warming-vs-climate-change/. Accessed 29 January 2023.
“Polar bear | Description, Habitat, & Facts | Britannica.” Encyclopedia Britannica, 5 December 2022, https://www.britannica.com/animal/polar-bear. Accessed 29 January 2023.
“Polar Bears and Climate Change | Pages | WWF.” World Wildlife Fund, https://www.worldwildlife.org/pages/polar-bears-and-climate-change. Accessed 29 January 2023.
“Polar bears and climate change: What does the science say?” Carbon Brief, 7 December 2022, https://interactive.carbonbrief.org/polar-bears-climate-change-what-does-science-say/. Accessed 29 January 2023.
“Polar bears and climate change: What does the science say?” Carbon Brief, 7 December 2022, https://interactive.carbonbrief.org/polar-bears-climate-change-what-does-science-say/. Accessed 29 January 2023.
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