Researchers say greenhouse gas emissions are helping push polar bears toward extinction by 2100

A July 20 research report highlights that high greenhouse gas emissions are contributing to the potential extinction of polar bears by the year 2100.

Published in the Nature Climate Change journal, an abstract for "Fasting season length sets temporal limits for global polar bear persistence" describes how the animals are being impacted by global warming and declines in sea ice — something that polar bears require to capture seals, a main food source for the species.

The researchers said, as of yet, it had not been possible to forecast when different subpopulations of polar bears would decline because data that linked ice availability to a particular demographic’s performance was unavailable and "unobtainable a priori for the projected but yet-to-be-observed low ice extremes."

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"We establish the likely nature, timing and order of future demographic impacts by estimating the threshold numbers of days that polar bears can fast before cub recruitment and/or adult survival are impacted and decline rapidly," researchers said in the abstract. "Intersecting these fasting impact thresholds with projected numbers of ice-free days, estimated from a large ensemble of an Earth system model, reveals when demographic impacts will likely occur in different subpopulations across the Arctic."

After using their model to observe trends from 1979 to 2016, the researchers noted that survival impact thresholds may have "already been exceeded" in some polar bear subpopulations. Their findings also suggest that with greenhouse gas emissions, "steeply declining reproduction and survival will jeopardize the persistence of all but a few high-Arctic subpopulations by 2100."

Sadly, the researchers noted that even with moderate mitigation of emissions, those actions are "unlikely to prevent some subpopulation extirpations within this century."

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The harms of global warming on vulnerable animal populations has been heavily researched over the past few decades. The World Wildlife Foundation (WWF) highlights how climate change is impacting species such as the African elephant and giant panda, as well as larger places and ecosystems including the Coral Triangle and the Eastern Himalayas.

As for the Arctic, the WWF notes that greenhouse gases are prompting temperatures to rise at an increased rate, "resulting in lower levels of sea ice, melting permafrost and rising sea levels all over the world." 

That loss of sea ice has severely impacted polar bear population counts. The nonprofit Polar Bears International said that according to 2018 estimates, there were around 23,000 of the animals left in the world.