The decline in populations of Arctic polar bears is due to the ever-increasing temperatures of Earth due to climate change. According to a new study conducted by the U.S. Geological Survey (USGS), greenhouse gas emissions are the biggest threat to the existence of polar bears. The new study shows that increasing average temperature Earth could cause an extinction-level event for polar bears by 2100.
The USGS study looked at four ecoregions in the Arctic Circle, areas with divergent, convergent, archipelago, and seasonal ice. By using sea ice data from the UN’s Intergovernmental Panel on Climate Change to create forecast models to the end of the century, researchers were able to create two scenarios with different levels of greenhouse gas emissions. The first scenario gave scientists and idea of how reduced greenhouse gas emissions could affect polar bears, and the second showed the current rates of increase if nothing is done to slow emissions.
Researchers found that with the current rate of climb in the Earth’s temperature, the loss of all four subregions of ice in the Arctic circle is the greatest extinction-level threat to polar bears. Mike Runge, a research ecologist with the USGS, stated policymakers across the globe need to address the increasing rates of sea ice loss. Moreover, he said, “Because carbon emissions accumulate over time, there will be a lag, likely on the order of several decades, between mitigation of emissions and meaningful stabilization of sea ice loss.” Therefore, policy solutions need to be made years in advance to combat the environmental doomsday.
Under the heavy greenhouse gas emissions scenario, levels of divergent and convergent ice will greatly decrease nearly 25 years earlier than if carbon emissions were regulated even stricter. When examining the stabilized scenario, greenhouse gas emissions peak near 2040, and then begin to decline into 2080, and through the end of the century. Scientists believe during this stage, archipelago ice in the high-latitude regions of the Canadian Arctic will be all that is left by 2100. This is the region where ice is present longer during summer months. The archipelago ecoregions will be a key natural refuge for polar bears nearing the end of the century.
Some claim that environmental stressors like oil and gas exploration, sea mining, and shipping routes are causing polar bear populations to decline. However, Todd Atwood, a research biologist with the USGS and lead author of the study, stated these human-induced stressors to the Arctic region, “had only negligible effects on polar bear populations—compared to the much larger effects of sea ice loss and associated declines in their ability to access prey.”
The researchers also found that if ice-free periods in the summer last for longer than four months, polar bear populations will die off even quicker. These Arctic animals depend on ice to be able to travel to where sources of food are located. When the bears retreat inland, their food supply is essentially cut off.
The USGS study shows that managing man-made environmental disasters other than greenhouse gas emissions could possibly lessen the blow to the polar bear population worldwide. However, much of the damage has already been done, and it is irreversible. Scientists believe the only way to ensure the survival of polar bear through 2100 is to, “limit global warming to less than 2°C above preindustrial levels.” With that said, based on USGS’s study, the extinction of Arctic polar bears could possibly happen by the end of the century – all because of man-made greenhouse gas emissions.
By Alex Lemieux
USGS: Greenhouse Gas Emissions Remain the Primary Threat to Polar Bears
USGS: Evaluating and Ranking Threats to the Long-Term Persistence of Polar Bears
USGS: Changing Arctic Ecosystems Initiative
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