Polar bears (Ursus maritimus) have survived for centuries the main threat to their survival, hunting, but now they face new challenges that have arisen or been caused by humans. The greatest of these dangers is climate change, which alters the living conditions of this and many other species of animals and plants in regions as sensitive to rising temperatures as the Arctic.
There is no doubt, and this has been shown by various studies and observations in recent years, that global warming is reducing ice masses, especially those floating in the Arctic Ocean, and this circumstance makes movement, reproduction and feeding difficult. of polar bears (which cannot easily locate and hunt their prey in the absence of ice). This is an example of the relationship between climate change and the survival of the so-called white bear.
A study led by researchers from the University of Washington and the organization Polar Bears International, in Bozeman (United States), now for the first time quantifies the relationship between greenhouse gas emissions (causing climate change) and the survival of polar bear populations. One of the objectives of this study is to provide specific data that makes possible the application in the United States of a law that states that new activities that produce greenhouse gases cannot be authorized if it is shown that these emissions cause damage to protected species.
An article by these authors published this week in the journal Science presents the results of “combining established research with new analysis to provide a quantitative link between greenhouse gas emissions and polar bear survival rates.” , as reiterated by the University of Washington in a note presenting the results of the work of its researchers.
Reviewing the data already known, the authors recall that “the warming of the Arctic is limiting the access of polar bears to sea ice, which these animals use as a hunting platform.” “In the ice-free summer months, the bears must fast. Although in the worst case the adult bears will die, before they lose the ability to raise cubs successfully,” they indicate.
“Until now, scientists have not offered quantitative evidence to link greenhouse gas emissions to population decline,” explains Cecilia Bitz, study co-author and professor of atmospheric sciences at the University of Washington.
Bitz and his team conducted data analysis for the new report showing a direct link between greenhouse gas emissions (such as CO?) and changing polar bear demographics. The link largely explains recent downward trends in some polar bear subpopulations, such as in western Hudson Bay. The document also has political implications because it allows for a formal assessment of how future proposed actions – such as new hydrocarbon-firing plants – would affect polar bears.
“I hope the United States government meets its legal obligation to protect polar bears by limiting greenhouse gas emissions from human activity,” Bitz said in statements released by his university. “I hope that investments are made in alternatives to fossil fuels that exist today and that new technologies are discovered that avoid greenhouse gas emissions,” the atmospheric researcher specifies.
In 2008, polar bears became the first species listed under the US Endangered Species Act due to the threat of climate change. The biological link between warming and the survival of polar bears was clear, and scientists projected that up to two-thirds of the world’s polar bears could be extinct by mid-century.
The Endangered Species Act requires that any project authorized by the US government, including oil and gas development, not place any protected-listed species in further jeopardy. But a document published by the US Department of the Interior in 2008, known as the Bernhardt Opinion, required for the application of this law specific evidence of how greenhouse gas emissions from a proposed project would affect the survival of a species. before the law could be fully implemented for species threatened by climate change.
“We have known for decades that continued warming and loss of sea ice can ultimately only result in a decline in the distribution and abundance of polar bears,” said Steven Amstrup, lead author of the new study, lead investigator emeritus of Polar Bears International and an adjunct professor at the University of Wyoming. “In this new paper, we reveal a direct link between anthropogenic greenhouse gas emissions and bear cub survival rates,” says Amstrup.
The new article, published coinciding with the 50th anniversary of the US Endangered Species Act and the 15th anniversary of the listing of polar bears, provides what its authors consider “new scientific evidence” to answer questions legal requirements such as the Bernhardt Opinion, the authors reiterate the study.
Advances in climate science mean that precise links between emissions and species survival can now be made. Bitz was also a co-author of a study published in Nature Climate Change in 2020 that presented a model for polar bear survival in the face of declining sea ice, connecting polar bear fasting to ice-free days and calculating the limits of annual fasting leading to mortality. This 2020 study considered not only the survival of adult polar bears, but also their reproductive success, that is, their ability to bear cubs and raise them to the age at which they become independent from their mothers.
The new paper links ice-free days and fasting limits for polar bears to cumulative greenhouse gas emissions. It finds that, for example, the hundreds of power plants in the United States will emit more than 60 gigatons of greenhouse gas emissions during their 30-year lifetime, which would reduce the survival of polar bear cubs in the population of the United States. southern Beaufort Sea by about 4%.
“Overcoming the challenge of the Bernhardt Opinion absolutely belongs to the realm of climate research,” says Professor Bitz. “When the memo was drafted in 2008, we couldn’t say how human-generated greenhouse gas emissions equated to a decline in polar bear populations. But within a few years we could directly relate the amount of emissions to climate warming and, later, also to the loss of sea ice in the Arctic. “Our study shows that not only sea ice, but also the survival of polar bears may be directly linked to our greenhouse gas emissions.”
According to the authors, the new study has implications beyond polar bears and sea ice. The same method of analysis can be adapted to other species and habitats of species with direct connections to global warming, such as coral reefs, the endangered Key deer residing in the Florida Keys, or nesting species. on the beaches and that are affected by the rise in sea level.
“Polar bears are beautiful creatures and I hope they survive global warming. However, the health and well-being of human beings, especially the most vulnerable, is of the utmost importance”, explains Bitz, expanding the limits of studies such as his. “All of us have experienced extreme heat in recent years. The damage is inescapable.
“Everything that governments and industries can do to reduce greenhouse gas emissions is important and will help avoid the worst consequences, concludes Professor Bitz.
