Minding the Sciences — Smarter Than Your Average Bears


Remember those pathetic photographs of polar bears standing on tiny ice floes, scanning the horizon for the tasty seals that were no longer there? Those viral photos of an emaciated polar bear, starving because its prey has disappeared along with the sea ice that has melted away due to climate change? The very same photos for which National Geographic had to apologize for publishing such blatantly deceptive climate agitprop? The starving-polar-bears climate narrative collapsed so spectacularly that even The Guardian had to say that maybe it’s time to dial back on the polar bear porn.

Nevertheless, the polar bear remains a popular avatar for climate change activism. National Geographic still has the starving polar bear footage on its YouTube channel. Alamy, the stock photo site, has dozens of starving polar bear photos just in case one is needed for a fundraising campaign. And polar bears are very useful for dragooning science into the service of climate activism. A late August edition of Science, features an example of such activism: “Unlock the Endangered Species Act to address GHG emissions.” The Endangered Species Act (ESA) is “locked”? I had no idea, but apparently it is, at least according to the article’s authors, who complain that the ESA contains an inconvenient provision that blocks using polar bears as a wedge to force nations to scale back fossil fuels. “Unlocking” the ESA means finding a way around that barrier.

The provision, known as the Bernhardt Memorandum, constrains how the U.S. Department of the Interior may use the ESA to mitigate the effects of greenhouse gas emissions. Specifically, the memorandum specifies that “impacts” requiring mitigation should be traceable to a specific source. If a city dumps sewage into a river, for example, and an endangered species of fish living downstream is harmed thereby, the ESA can be used to force mitigation—that is, to impose changes in how the city handles its sewage.

With respect to greenhouse gases, the Bernhardt Memorandum opined that the sources of greenhouse gases were too diffuse to qualify for what the ESA can claim as a “source.” The United States contributes only 15 percent of global CO2 emissions. The bulk of the remainder (30%) comes from China, the European Union (9%), India (7%), Russia (5%), and Japan (4%), with the rest coming from the other 162 countries in the world, including Canada. The Bernhardt Memorandum is what the authors of the Science paper want to “unlock.” To do so, a firm chain of causation needs to be established between greenhouse gas emissions and harm to polar bears.

The hurdle is that the plight of polar bears is a myth. Polar bear populations were once estimated to be near a perilous 5,000. However, as methods for estimating wildlife populations have improved, so has the estimated number of polar bears worldwide. A 2018 report pins the current number closer to 25,000 to 30,000 and rising. Polar bears, in other words, are a conservation success story, owing more to better management of seal populations, and better regulation of Inuit traditional hunting limits than climate change. This is why polar bears are classified as “threatened” or “vulnerable” rather than “endangered.” To bring polar bears under the umbrella of the ESA, they must be reclassified as endangered. To do that, a different measure of harm is needed.

The authors of Science’s article argue that demographics, not populations, is the better measure. We just haven’t seen the harmful effects yet, the argument goes, but we will see it further down the road as future cohorts of polar bears come into breeding age. Fewer bear cubs born now will result in fewer breeding bears in the future, with demographic collapse being the eventual outcome.

The authors’ metric for assessing harm is “fasting duration” (FD). When polar bears come out of hibernation, they seek sea ice, where their preferred prey, ringed seals, may be found. Once they have feasted and built up their fat reserves, the bears migrate back to land where the sows have cubs and nurse, all the while fasting and depleting those built-up fat reserves. In a warming Arctic, the argument goes, it will take longer for the bears to find sea ice suitable for hunting seals and shorten the time that seals will be found on sea ice. From the prolonged fasting duration, there will follow a reduction of fecundity.

The ESA obliges agencies to follow the “best science” available. Is the Science paper now the “best science” on polar bears? The paper’s authors think so, claiming to have “confirmed the direct link between [greenhouse gas emissions] and polar bear demography.” As a result, “the Department of the Interior now has the scientific justification to rescind” the Bernhardt Memorandum and so “provide the government an important and previously unavailable tool for addressing anthropogenic climate warming.” This means empowering the Department of Interior to mandate immediate reductions in greenhouse gas emissions, which amounts to phasing out fossil fuels.

Fasting duration for four populations of polar bears, plotted versus cumulative emissions of gigatonnes greenhouse gases to the atmosphere. Amstrup and Bitz, Science 381(6661): 949-951 (2023).

The link is not as clear-cut as the Science paper’s authors might think. The centerpiece of their argument is a series of graphs that depict longer annual fasting durations since 1979 versus cumulative emissions of greenhouse gases. Cumulative emissions add each year’s emissions to the summed emissions of all the previous years, so that the number always increases over time, irrespective of annual emissions, or whether they might rise or fall from year to year. From this, and other studies of the energy cost of polar bear reproduction, the authors derive what they claim is a precise correlation: fasting duration increases by two-and-a-half to three days each year as greenhouse gases accumulate.

Cumulative emissions of greenhouse gases are a curious choice for the x-axis. Carbon dioxide cycles in and out of the atmosphere quickly, methane more so, and water vapor more quickly still. A more direct climate link might have been provided by correlating the annual observed fasting duration against the annual observed variation of arctic sea ice. After all, it is the year-to-year paucity of sea ice that is presumed to be prolonging the fasting duration. Those data would likely have been less congenial. While long-term trends in the extent of Arctic sea ice show a small decline from 1979 to 2010, they have been rising since 2017 or so. Would polar bear fecundity for those years show an increase? Not if the fasting duration were buried under the steadily increasing weight of cumulative emissions.

The extent of sea ice globally (top trace), in the Arctic (middle trace) and Antarctic (bottom trace) from 1979 through August 2023. The red line is the average extent, the large annual swings are annual variations, and the small annual swings are the 13-month running average. Source: Climate4You.

Another odd feature of the data is those points in the graphs: How were these point data obtained? Had teams of researchers fanned out over all these regions and painstakingly observed the comings and goings of the local polar bears? No, not quite. Field observations of this sort are extraordinarily challenging. Observing the comings and goings of polar bears requires placing radio collars, which often come off or malfunction. Direct observations were only done for the polar bear populations around Hudson Bay, where such measurements are feasible. For the other eighteen populations distributed around the Arctic Ocean and archipelago, the Science authors used satellite observations of the local extent of sea ice, and used the Hudson Bay data to estimate fasting durations there. This explains why the extent of sea ice was not the x-axis in their plots: fasting duration was in fact an estimate derived from the extent of sea ice. So, the apparent point data for fasting durations are not direct observations, but statistical inferences based on the comings and goings of sea ice.

The Science paper is an exemplar of a common problem with “climate science”: it presents its conclusions as well-established scientific facts, when they are actually chains of statistical inferences, each carrying a burden of uncertainty. Presenting fasting durations as points, as the Science paper did, is misleading because it obscures the inherent uncertainty surrounding those points, which would have been better represented as diffuse blobs rather than points. The uncertainty is considerable, compounded by a chain of uncertainty that builds with every link the authors use to connect greenhouse gas emissions to polar bear demography. For example, what is the likelihood that a statistical model of fasting duration at one well-studied population (Hudson Bay) can be extended to the nineteen distinctive polar bear habitats in the Arctic? We don’t know. Estimates of fecundity derived from fasting duration are themselves statistical inferences, with their own set of errors, as are models for the metabolic costs for foraging, birthing, and nursing. And so, inference is piled on inference, compounding the uncertainty at every step. Even granting the authors’ assertion that their study represents the best science available, it remains weak science.

There is another common problem with “climate science”: it sits positioned deliberately at the intersection between science and political activism, which are opposing virtues. The Science paper has a clear political aim: to remove an administrative obstacle to using polar bears as a tool to force reductions in fossil fuels. This is not speculation: it’s stated in the paper’s title, and in the text of the Science paper and other publications by the same authors. How do the Science paper’s authors balance the opposing virtues of science and activism? The Science paper’s senior author is the Chief Scientist at an activist group, Polar Bears International, which operates as a registered charity in both the United States and Canada. Groups like Polar Bears International depend upon charitable donations, which amounted to about 93% of their $4.9 million revenues for 2022. Scientists working for Polar Bears International must therefore be attentive to donors’ motivations: should the scientists in their employ discover that polar bears will probably be OK after all, donations to Polar Bears International will likely dry up. Motivation matters, in other words.

Should this serve as a pretext to dismiss the Science paper out of hand? Actually, I would say no. The Science paper lays out an interesting argument, albeit an unpersuasive one, in my view. They weren’t dishonest: there was some data prestidigitation at work, to be sure, although you’d have to dig deeply into the supplemental data of the paper and other publications by the same authors to uncover it. And to be frank, competing motivations is simply a fact of life in science. Is this a bad thing, an example of politics corrupting objective science? Not necessarily.

Polar Bears International is one of several polar bear conservation charities, all competing for donors who may themselves bring a variety of motivations to their donations. The conservative-leaning Heartland Institute, for example, also has scientists engaged in polar bear conservation. It is a fair bet that the Heartland Institute’s polar bear conservation efforts will attract a different set of donors with different motivations than those who would contribute to Polar Bears International.

The result is something approaching a scientific free market, where different scientific points of view contend and jostle for funds, just as providers of goods and services do. Competition for donors may actually strengthen polar bear science, not weaken it. This free market of ideas has, for example, brought out just how resilient polar bears are in the face of a changing climate, no matter what the cause. For example, if seals are absent or difficult to come by, we know polar bears will hunt reindeer,  or colonies of sea birds, or even forage trash. When sea ice is absent, as it is for eight months of the year in Greenland’s fjords, polar bears hunt differently, floating along on floes calved from glaciers. Polar bears, it seems, are more clever than we give them credit for. It took a scientific free market to bring those nuances to light. Competition for donors may actually be strengthening polar bear science, not weakening it.

So, the question for polar bear science, indeed for science generally, is how best to foster a scientific free market of ideas? It once was the case that universities were the natural home for that. As government and corporate interests have come to dominate university funding, including research, the academic intellectual free market is finding itself increasingly crushed under pressure to conform to the political agendas of its paymasters.

The future of intellectual diversity may therefore lie in competition between private entities which reflect the diversity of thought of donors making free choices about the charitable use of their money. This is one reason why the NAS supports this kind of independent science, as a haven for scientists to do their science outside the completely politicized academy-government-corporate complex.

Editor’s Note: This piece is part of a new Minding the Campus article series called Minding the Sciences, wherein we are renewing our focus on the sciences given the many threats it faces in modern academia. Click here to learn more.

Image: Adobe Stock


  • J. Scott Turner

    J. Scott Turner is the author of The Extended Organism: The Physiology of Animal-Built Structures (Harvard University Press, 2000). He is also director of the Prometheus Project at the National Association of Scholars.

3 thoughts on “Minding the Sciences — Smarter Than Your Average Bears

  1. Yes, polar bears are at the top end of a chain of feeding that starts at the microscopic. What has seemed to be most effective at protecting polar bear populations has been managing what polar bears eat. When harvesting of baby seals was banned in Canada, polar bears got a boost, just because there was now more food for polar bears. Similarly, polar bear populations are susceptible to the indigenous traditional hunt quotas allocated to the Inuit and other arctic tribes. What effect would managing that have on polar bear demography compared to reducing GHG emissions? The authors don’t say, really.

  2. OK. Polar Bears eat Ringed Seals. So what do Ringed Seals eat?

    Ringed Seals eat Herring.

    And what do Herring eat? Herring eat Krill.

    And what do Krill eat? Krill eat phytoplankton.

    Phytoplankton are (essentially) plants — they use sunlight and carbon dioxide to create food. So more carbon dioxide means more phytoplankton, which means more krill, which means more herring, which means more seals and thus more bears….

    But there’s a larger issue here that isn’t mentioned when people talk about sea surface temperatures, that of hurricanes. Hurricanes apparently bring up a lot of deeper (colder) water, to the point where a recent hurricane heading for the Gulf of Maine was greatly weakened when it went through the wake of an earlier hurricane.

    Well then, it would appear to matter where you take your surface temperature readings, and how recently a hurricane has gone through the area. And I’ve never seen either adjusted into the water temperature estimates.

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