THIS POST IS A CRITICAL COMMENTARY ON THE CLIMATE SCIENCE ASSUMPTION IN POLAR BEAR RESEARCH THAT OBSERVED CHANGES IN POLAR BEAR COUNTS AND PHYSICAL CONDITIONS OVER DECADAL TIME SCALES CAN BE UNDERSTOOD IN TERMS OF REDUCED SEA ICE EXTENT AND THEREFORE IN TERMS OF CLIMATE CHANGE WITH THE IMPLICATION THAT WE CAN SAVE POLAR BEARS BY TAKING CLIMATE ACTION.
PART-1: THE VIEW FROM CLIMATE SCIENCE AND THE MEDIA
- Fasting season length sets temporal limits for global polar bear persistence. Péter K. Molnár ETAL, Nature Climate Change volume 10, (2020): Abstract: Polar bears require sea ice for capturing seals and are expected to decline range-wide as global warming and sea-ice loss continue. Estimating when different subpopulations will likely begin to decline has not been possible to date because data linking ice availability to demographic performance are unavailable for most subpopulations and unobtainable a priori for the projected but yet-to-be-observed low ice extremes. Here, 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. Intersecting these fasting impact thresholds with projected numbers of ice-free days, estimated from a large ensemble of an Earth system models, reveals when demographic impacts will likely occur in different subpopulations across the Arctic. Our model captures demographic trends observed during 1979–2016, showing that recruitment and survival impact thresholds may already have been exceeded in some subpopulations. It also suggests that, with high greenhouse gas emissions, steeply declining reproduction and survival will jeopardize the persistence of all but a few high-Arctic subpopulations by 2100. Moderate emissions mitigation prolongs persistence but is unlikely to prevent some subpopulation extirpations within this century.
- NEW YORK TIMES: https://www.nytimes.com/2020/07/20/climate/polar-bear-extinction.html July 20, 2020: CITING THE MOLNAR PAPER: Polar bears could become nearly extinct by the end of the century as a result of shrinking sea ice in the Arctic if global warming continues unabated. Nearly all of the 19 subpopulations of polar bears, from the Beaufort Sea off Alaska to the Siberian Arctic, would face being wiped out because the loss of sea ice would force the animals onto land and away from their food supplies for longer periods. Prolonged fasting, and reduced nursing of cubs by mothers, would lead to rapid declines in reproduction and survival.
- There are about 25,000 polar bears in the Arctic. Their main habitat is sea ice, where they hunt seals by waiting for them to surface at holes in the ice. In some areas the bears remain on the ice year round, but in others the melting in spring and summer forces them to come ashore. They need the sea ice to capture their food. There’s not enough food on land to sustain a polar bear population. But bears can fast for months, (8 months). Arctic sea ice grows in the winter and melts and retreats in spring and summer. As the region has warmed rapidly in recent decades, sea ice extent in summer has declined by about 13 percent per decade compared to the 1981-2010 average. Some parts of the Arctic that previously had ice year-round now have ice-free periods in summer. Other parts are now free of ice for a longer portion of the year than in the past. The Molnar paper studied 13 of the subpopulations equal to 80 percent of the total bear population. They calculated the bears’ energy requirements in order to determine how long they could survive or, in the case of females, survive and nurse their cubs while fasting. Combining that with climate-model projections of ice-free days to 2100 they found that, for almost all of the subpopulations, the time that the animals would be forced to fast would eventually exceed the time that they are capable of fasting. The animals would starve. Longer fasting time also means a shorter feeding period. Not only do the bears have to fast for longer and need more energy to get through this, they also have a harder time to accumulate this energy. While fasting, bears move as little as possible to conserve energy. But sea-ice loss and population declines require having to expend more energy searching for a mate and that also affects survival. Even under more modest warming projections, in which greenhouse gas emissions peak by 2040 and then begin to decline, many of the subgroups would still be wiped out. Over the years, polar bears have become a symbol both for those who argue that urgent action on global warming is needed and for those who claim that climate change is not happening or, at best, that the issue is overblown. Groups including the Cato Institute, a libertarian research organization that challenges aspects of climate change, have called concerns about the bears unwarranted, arguing that some research shows that the animals have survived repeated warm periods. But scientists say during earlier warm periods the bears probably had significant alternative food sources, notably whales, that they do not have today. Poignant images of bears on isolated ice floes or roaming land in search of food have been used by conservation groups and others to showcase the need for action to reduce warming. Occasionally, though, these images have been shown to be not what they seem. After a video of an emaciated bear picking through garbage cans in the Canadian Arctic was posted online by National Geographic in 2017, the magazine acknowledged that the bear’s condition might not be related to climate change. Scientists had pointed out that there was no way of knowing what was wrong with the bear; it might have been sick or very old. The new research did not include projections in which emissions were reduced drastically, said Cecilia M. Bitz, an atmospheric scientist at the University of Washington and an author of the study. The research needs to be able to determine the periods when sea ice would be gone from a particular region. Andrew Derocher, a polar bear researcher at the University of Alberta said the findings “are very consistent with what we’re seeing” from, for instance, monitoring the animals in the wild. “The study shows clearly that polar bears are going to do better with less warming,” he added. “But no matter which scenario you look at, there are serious concerns about conservation of the species. Of the 19 subpopulations, little is known about some of them, particularly those in the Russian Arctic. Of subpopulations that have been studied, some generally sub-populations in areas with less ice loss have shown little population decline so far. But others, notably in the southern Beaufort Sea off northeastern Alaska, and in the western Hudson Bay in Canada, have been severely affected by loss of sea ice. One analysis found that the Southern Beaufort Sea subpopulation declined by 40 percent, to about 900 bears, in the first decade of this century (2000-2010) . Derocher said one drawback with studies like these is that, while they can show the long-term trends, it becomes very difficult to model what is happening from year to year. Polar bear populations can be very susceptible to drastic year-to-year changes in conditions, he said. “One of the big conservation challenges is that one or two bad years can take down a sub-population that is healthy and push it to really low levels.
BIASED RESEARCH QUESTION AND METHODOLOGY WITH AN EXCLUSIVE FOCUS ON SEA ICE EXTENT AS THE ONLY DETERMINANT OF POLAR BEAR SUB-POPULATION DYNAMICS: As seen in the variables listed below that are known to affect polar bear subpopulation dynamics, it is a gross over-simplification to interpret these dynamics purely in terms of summer minimum sea ice extent. Human predation of polar bears in terms of hunting for food and hide has been a feature of polar bear subpopulation dynamics (PBSPD) for thousands of years. Its intensity increased sharply 500 years ago when commercial bear hide trade boomed and again 70 years ago when snowmobiles, speed boats, and aircraft were employed in the post war explosion of the bear hide business. It is widely believed that polar bear hunting has now been banned but this is not true outside of Norway and some regions of Siberia where some restrictions have been placed on polar bear hunting. Native Arctic humans that have always hunted polar bears for food, clothing, and other purposes have no restrictions. However, polar bear hunting by outsiders is restricted by an international agreement that forbids the use of snowmobiles, speedboats, and aircraft in these hunts. This agreement does not prohibit hunting of polar bears for hide. Non-human predation: in addition to human predation, we find that young polar bears cubs are hunted by wolves and by adult polar bears for food. Starving nursing mothers may also feast on her cubs. In general Intra-species predation is prevalent among polar bears where strong young males may feast on cubs or weaker females. Also, fighting among males for mating partners or hunting rights may also result in death and cannibalism. Polar bears may look cute and cuddly but they are not as nice as they look.
NON-CLIMATE FACTORS IN POLAR BEAR SUB-POPULATION DYNAMICS
LONGEVITY: Generally 20 to 30 years but as low as 15 and as high as 32. You can tell how old it is by looking at a thin slice of tooth and counting the layers. PREDATION: Adult polar bears have no predators except other polar bears but cubs less than one year old sometimes are prey to wolves and other carnivores and newborns may be eaten by the polar bears themselves especially if the mother is starved. INTRA-SPECIES PREDATION: This does not happen a lot but males fight over females and will kill the competition to get the lady he wants. In extreme hunger conditions, male polar bears may attack, kill, and eat female polar bears. This is not a normal behavior pattern but it does happen. HUMAN PREDATION: Humans have hunted, killed, and eaten Polar bears for thousands of years. Arctic people have traditionally hunted polar bears for food, clothing, bedding, and religious purposes. More recently commercial hunting for polar bear hides got started more than 500 years ago. There was a sharp rise in the kill rate in the 1950s when modern equipment such as snowmobiles, speedboats, and aircraft were employed in the polar bear hide trade. The hunt expanded to what was eventually viewed as a threat to the survival of the species and an International Agreement was signed in 1973 to ban the use of aircraft and speed boats in polar bear hunts although hunting continued to the extent that they were still the leading cause of polar bear mortality. It is popularly believed that polar bear hunting is now banned. STATE OF HUMAN PREDATION: Today, polar bears are hunted by native arctic populations for food, clothing, handicrafts, and sale of skins. Polar bears are also killed in defense of people or property. However, hunting is strictly regulated in Canada, Greenland, Norway, and Russia. In Norway and Russia hunting polar bears is banned. CLIMATE CHANGE IMPACT: Increasing temperatures are associated with a decrease in sea ice both in terms of how much sea ice there is and how many months a year they are there. Polar bears use sea ice as a platform to prey mainly on ringed and bearded seals. Therefore, a decline in sea ice extent reduces the polar bear’s ability to hunt for seals and can cause bears to starve or at least to be malnourished. YOUNG POLAR BEARS: Subadults are inexperienced hunters, and often are chased from kills by larger adults. OLD & WEAK BEARS are also susceptible to starvation for the same reason. They can’t compete with younger and stronger bears. In hunt constrained situations, as in limited sea ice, kids and seniors starve first. Climate change scientists have found (bibliography in related post) that polar bear subpopulations have shown increasing evidence of food deprivation including an increase in the number of underweight or starving bears, smaller bears, fewer cubs, and cubs that don’t survive into adulthood partially because in food constrained situations cubs are more likely to be eaten by adult polar bears. This takes place in areas that are experiencing shorter hunting seasons with limited access to sea ice. These conditions limit the bears’ ability to hunt for seals.
The implication for climate impact studies is that a comparison of polar bear subpopulation counts across time at brief decadal time scales, in and of itself, may not have a climate change sea ice interpretation because of the number of other variables involved in these dynamics.
Yet another factor is the assumption that observed changes in September minimum sea ice extent are driven by global warming such that they can be moderated by taking climate action by reducing or eliminating the use of fossil fuels. This critical causal relationship is simply assumed in climate science. However, as shown in related posts: LINK: https://tambonthongchai.com/2020/09/25/list-of-arctic-sea-ice-posts/ , detrended correlation analysis does not show that September minimum Arctic sea ice extent is responsive to air temperature above the Arctic. This means that we have no evidence to support he assumption that fossil fuel emissions cause lower September minimum sea ice extent and that this trend can be attenuated by taking climate action. Thus, in short, the two critical causations in polar bear research by climate scientists, (1) that fossil fuel emissions lower September minimum sea ice extent and (2) that polar bear sub-population dynamics are the creation of changes in September minimum sea ice extent, are simply assumed with no empirical evidence provided to support them.
Whether the polar bears are in trouble is not the issue. The only issue is whether their trouble if any is caused by fossil fuel emissions and whether it can be moderated by taking climate action. This important aspect of the polar bear issue in climate science is missing from polar bear research carried out by climate science apparently to provide the needed motivation for climate action.