More polar bear shenanigans from scientists and NatGeo
- Ivo Vegter
- 06 Feb 2018 01:28 (South Africa)
National Geographic, spurred on by shoddy science, has been writing sensational but untrue headlines again. Headlines like: “Polar Bears Really Are Starving Because of Global Warming, Study Shows”.
No, they really are not starving, and no, the study doesn’t show that.
Perhaps the writers at NatGeo were a little sensitive over their last polar bear faux pas, in which they brazenly misrepresented a video of a single starving polar bear as illustrative of what was happening to polar bears in general because of a lack of sea ice. This new article opens with a long self-justifying paragraph about that fiasco, admitting that it was “controversial” and “ignited a firestorm of debate”, and that “it’s impossible to know for sure what ailed that individual”. Whatever it was, it wasn’t climate change that ailed it.
The latest story is based on a study conducted by Anthony Pagano and others, entitled “High-energy, high-fat lifestyle challenges an Arctic apex predator, the polar bear”. It claims to have studied the feeding habits and metabolic rates of polar bears. It concluded that loss of sea ice habitat makes it harder for the animals to acquire sufficient food to meet their energy needs, which – the authors speculated – are likely to have a negative effect on reproductive success, and ultimately on polar bear populations.
It isn’t a really strong study. It is a really, really weak study. It is so weak that one should not draw any conclusions from it at all. How on earth it passed peer review to get published in Science is a mystery. Perhaps it just chimes with the journal’s own confirmation bias.
Let me explain why I say it is a weak study. For a start – and this should be quite enough to disqualify it as serious science – it was conducted on a sample of nine polar bears. Nine. For some of its results, the study relied on as few as five bears. There was no attempt to show that this tiny handful of bears was statistically representative of any population, or that the results were statistically significant. That’s probably because they couldn’t possibly have been, with such a small sample.
NatGeo’s “best estimate” population numbers of 20,000 to 30,000 polar bears is inaccurate, and lower than the IUCN’s estimate of 22,000 to 31,000, which itself is considerably higher than its past estimates of 20,000 to 25,000. The magazine claims that there are four polar bear populations that are declining, while five are stable, and the status of the rest is unknown. This is blatantly wrong, and also contradicts the latest data from the IUCN’s Polar Bear Specialist Group. As the WWF showed in this population chart, of the populations for which adequate data exists, two populations are on the increase, seven are stable, and only one is believed to be in decline.
Suspiciously, the Pagano study’s sample was selected from the sole declining polar bear population, those of the southern Beaufort Sea. This is cherry-picking of the worst kind, designed to bias the results to play into the researcher’s desired conclusion: that polar bears are not doing well.
The study says that the bears were studied during April of 2014 to 2016, “each year”. However, none of the results, charts or data suggests that any bear was studied more than once. The tracking map, for example, shows the movements of only nine bears, from first capture to recapture. All the other charts show only a single data point for each of the nine bears, showing that the bears were not studied in April of each year between 2014 and 2016. Each bear was studied only once. And the fact that different bears were studied in different years adds a confounding factor that is not addressed or even noted.
The bears were studied over a period of only eight to 11 days. Why the bears were only studied over such a short period of time is another mystery the study authors fail to explain. According to the WWF, a single 55kg seal can provide eight days’ worth of energy for a polar bear. The Pagano study itself says that an adult female in spring needs one adult seal every 10 to 12 days. If you’re only studying them for eight to 11 days, you’re bound to find a few that don’t feed during that time. In addition, any weight fluctuations over such a short period, in animals that can gain 20% of their body mass in a single meal, are bound to be temporary and unrepresentative of the longer-term health of the animals.
The WWF also reports that polar bears put on most of their weight annually between late April and mid-July. Pagano’s study doesn’t say exactly when in April the bears were studied, but the timing does seem to be awfully close to the end of the Arctic winter, in which little or no food is available to polar bears. If you’re looking at springtime weight gain, a study in May or June would have been more useful. The early timing would add yet another source of bias that plays into the desired narrative of starving bears.
The study admits that as a result of their capture and sedation, bears may have shown lower activity levels for as much as two or three of the eight to 11 days for which they were studied, which adds yet more bias, again in the same direction: the bears don’t eat enough.
The Pagano study cites “previous researchers” (which happen to include Pagano and Amstrup) as reporting that “42% of adult female polar bears in the Beaufort Sea during the spring from 2000 to 2016 had not eaten for “7 days before capture”. They continue: “This rate of fasting was 12% greater than measurements from 1983 to 1999, suggesting that spring ice conditions are affecting prey availability for polar bears even before the summer open water period.”
What it fails to point out is that the very same study reported the opposite effect in the Chukchi Seas, where fasting had become less frequent, which that study said was “consistent with studies demonstrating higher primary productivity and maintenance or improved body condition in polar bears, ringed seals, and bearded seals, despite recent sea ice loss in this region”.
That study also cites others which conclude that “global warming is expected to result in highly variable and difficult to predict changes in productivity of regional seas due to spatial variation in ice cover, stratification, and wind patterns”.
Wouldn’t do to mention data that contradicts your desired conclusions, now would it? Uncertainty and an inability to make predictions wouldn’t do if you’re trying to get into NatGeo.
As it is, with the sample size so small, the results of the latest Pagano study were all over the place. Four bears increased in mass, four decreased in mass, and one remained stable. Two didn’t eat, four ate once, one ate twice, and two ate three times over the very short study period.
One cannot conclude anything at all from these results. The sample is way too small, so the results are indistinguishable from chance. The population it was drawn from is known not to be representative. The study period was so short it could fall right between meals, making it impossible to conclude anything. The study’s authors wittingly omitted relevant data from other studies that they cited, and even co-wrote.
The Pagano study is so amateurishly terrible that it looks blatantly dishonest. But hey, it’s good enough for an alarming NatGeo headline. And that will greatly help Pagano and his mates to raise funds for their next trip to Alaska, where they can hang out taking pictures and tracking the occasional bear or two for a week.
When you read that polar bears are starving because of climate change, there not only is no good reason to believe it, but there are very good reasons to disbelieve it. It’s junk science by the researchers, and fake news by National Geographic. Simple as that. DM
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