Polar bears were listed as a threatened species 10 years ago. How are they faring now?
In this Q & A with Polar Bears International’s chief scientist, Dr. Steven Amstrup, we look at the history of the listing and where we are today.
Q: When and why were polar bears listed as threatened?
A: On May 14, 2008, the U.S. Secretary of the Interior, Dirk Kempthorne, announced his decision to list the polar bear as a threatened species under the Endangered Species Act, citing the ongoing and projected future decline of Arctic sea ice as a threat to their survival.
In a press conference at that time, Kempthorne said, “Because polar bears are vulnerable to this loss of habitat, they are—in my judgment—likely to become endangered in the foreseeable future.”
Q: You played a role in the listing. Can you tell us about that?
A: Prior to joining Polar Bears International as chief scientist, I was head of polar bear research in Alaska for 30 years. One of my last major tasks as a government scientist was to lead a U.S. Geological Survey research team in producing series of reports for the Interior Department. The findings in those reports convinced the Secretary that the polar bear’s future was indeed threatened by sea ice loss.
Q: When the listing was made, it was clear that action on climate change was urgently needed to save the sea ice that polar bears need for their survival. What has happened since then?
A: In 2010 my colleagues and I showed there is a linear, but inverse, relationship between global mean temperature and sea ice extent. More recently it has been shown this same linear relationship holds between CO2 concentrations and sea ice extent. This means that if we stop CO2 rise, we stop sea ice decline. Unfortunately, we have not stopped CO2 rise. and since polar bears were listed, the Arctic has lost another million square kilometers of summer sea ice and decline in winter ice extent has accelerated. The last five years have had weaker sea ice development than any other years on record.
Recent research has confirmed that bears stuck on land over most of the Arctic will be fasting because Arctic terrestrial habitats do not host foods rich enough to replace the seal diet that polar bears lose as sea ice availability declines. New work has confirmed that polar bears lose about a kilogram each day they stay on land. In Western Hudson Bay, bears are now on land for nearly a month longer than they were 30 years ago. Bears have an incredible ability to fast, but there is a limit!
And, new research reinforces our understanding of the importance of sea ice. We now know that the carbon composing polar bears’ bodies comes mainly from the tiny creatures that live on the underside of sea ice. Sea ice, therefore, is not just a hunting platform for polar bears, but the primary nutrition source for the food chain on which polar bears depend.
It’s also important to note that, all sea ice is not created equally. Our research in Alaska showed that polar bears prefer to feed on ice over the productive shallow continental shelf waters. Radiotracking bears in the Beaufort Sea revealed that they used to feed throughout the summer on that near-shore ice. With summer ice now retreating away from those shallow water areas, most bears follow the ice as it retreats over deep polar basin waters. It has long been known that these deep waters are relatively unproductive. New findings have revealed polar bears that follow the pack ice over the deep polar basin waters, apparently are, like those on land in Hudson Bay, food-deprived. This helps explain why the southern Beaufort Sea population, which I studied for 30 years, has declined by approximately 40%.
Although the relationships between CO2 temperature and average sea ice extent are largely linear, there are dangerous thresholds as we allow continued warming. The “average” sea ice extent is calculated from many individual years, and there is great variability among those years. An important threshold, from a polar bear perspective, is the frequency of ice-free summers as we go forward into a warmer world. In a world that is 2 degrees C warmer, we can anticipate the Arctic will be largely ice free every third summer, whereas if we were able to hold temperature rise to 1.5 degrees C, as was set as a goal at the Paris Climate talks in 2015, ice-free summers will occur only about 3% of the time.
And, the dangers of warming the world go far beyond polar bears. The difference between a 1.5 degrees C and 2 degrees C warmer world is literally an issue of remaining above water for some small island nations. New research has revealed that by mid-century water temperature and oxygen saturation values will be unrecognizable in 42% of marine protected areas, with continued business-as-usual warming. By the end of the century summer temperatures over most of the globe will hotter than anything we ever have experienced. Severe precipitation events, a long-predicted symptom of a warmer world, already are occurring more frequently in every part of the U.S, while worldwide drought frequency and intensity are increasing.
Yet, the U.S. has pulled out of the 2015 Paris Climate Agreement. which charted a path to a maximum of 2 degrees C warming (and a target of 1.5 degrees C)—a path that would assure polar bear survival over much of their current range. Instead current U.S. leadership is pushing us farther down the business as usual path toward polar bear extinction. Because all of the energy it contains comes from oxidizing carbon, coal is the single most dangerous of fossil fuels. Yet, the U.S. is pushing hard to expand the burning of coal. At the same time the U.S. is creating ever-more incentives for hydrocarbon development—including opening the previously protected polar bear denning areas in the Arctic National Wildlife Refuge to oil and gas exploration.
Even as they are compounding threats to the security of species worldwide, the current administration and our Congress have set their sights on reducing protections of the Endangered Species Act and has overturned the protections of the National Environmental Policy Act (NEPA), both of which have served our environment well since the Nixon Administration.
Q: How optimistic are you that we can save polar bears?
A: Since joining PBI, I’ve witnessed a great shift in public knowledge. Most people now understand that climate change is real, human-caused, and a threat to polar bear survival. Almost all countries of the world support action to reduce the emissions that are causing the planet to warm and the sea ice to melt—and individuals, cities, states, businesses, and universities are joining them in solutions. There are many encouraging changes taking place.
But U.S. leadership is sorely lacking. All citizens must do what they can to reduce personal carbon footprints. And most important we must vote for candidates at all levels of government who recognize the urgency and support action to halt climate change.
We know what we need to do to save polar bears and we know it is still possible. Now we need to turn that possibility into plausibility. Acting in time to save polar bears, also will ensure a better future for our children and grandchildren.