More Research Finds Polar Bears’ Condition Unaffected by Reduced Summer Sea Ice.
Although the Inuit steadfastly claim it is “the time of the most polar bears”, the most recent IUCN polar bear assessment predicts a 30% drop in the global polar bear population by mid‑century by assuming a linear correlation between summer sea ice melt and polar bear survival. They suggest bears “require sea ice to hunt” and thus predict less sea ice will prevent access to their preferred prey. However polar bear ecology and observations contradict that simplistic assertion. As listed below the current alarming predictions are due to extremely biased models and critical sins of omission presented in USGS publications, which ultimately misguide conservation efforts and the public’s understanding of the effects of climate change. Please petition congress to promote more reliable polar bear population studies and sign the petition here:
1) Greater than eighty percent of most polar bears’ annual stored fat is accumulated during the ringed seal pupping season that stretches from late March to the first week of May. Well‑documented observations (Stirling 2002, Harwood 2012, Chambellant 2012) report that cycles of heavy springtime sea ice have drastically reduced ringed seal reproduction. Heavy springtime ice is likely the greatest cause of polar bear nutritional deprivations, yet not one USGS model incorporates sea ice conditions during this critical time.
2) In areas like the Chukchi Sea that have experienced some of the greatest reductions in summer sea ice, there has been no reduction in polar bear body condition and some improvement (Rode 2014), contradicting USGS models driven by the hypothesis that less summer sea ice leads to nutritional deprivation.
3) All USGS models incorporate measures of minimal summer sea ice area in September despite the fact that ringed seals leave the ice in June, after pupping and molting, and swim in distant open waters. During this time less summer ice has little effect on the accessibility of seals.
4) USGS models assume more open water is detrimental to polar bears. But all published ecological studies (i.e. Harwood 2012, Chambellant 2012) show that ringed seal body condition, and thus seal reproductive outputs, decline when sea ice is slow to clear in the spring. It is longer periods of sea ice that cause lower ringed seal body condition and reproductive fitness that ultimately reduces the polar bears’ prey availability.
5) The IUCN’s assessment predicting a 30% decline in the global polar bear population is driven largely by the USGS’ models suggesting unique declining polar bear population in Southern Beaufort Sea’s. USGS models:
a. -calculated unrealistic bear survivorship estimates (0.77 here) during 2005 and 2006 based on mark and recapture models, that were unrealistic compared to known survivorship calculations of radio-collared bears (0.969 here) and survivorship estimates in 2002 to 2004. Only by uncritically embracing unrealistically low survivorship, USGS models created a dramatic drop in estimated abundance.
b. -blamed less summer ice and global warming for re‑capturing fewer bears, despite observations that heavy springtime sea ice had reduced seal ovulation rates to 30% in 2005 (Harwood 2012), the year models determined the lowest survivor rate for adult bears.
c. -ignored the 70% reduction in seal pups in 2005 due to heavy springtime ice that forced polar bears to increasingly hunt outside the USGS’ study area and making marked bears unavailable for re‑capture. As discussed here and here, the lack of recaptures due to temporary emigration is easily mistaken as a bear’s death. The USGS dismissed their own observations of increased transiency. And despite acknowledging an increased number of radio-collared bears outside the study area in 2005 and 2006, USGS modelers suggested that instead of searching elsewhere, bears just died, resulting in a dramatic population decline without the bodies to prove it.
d. -never published calculations of biological survival for known radio‑collared bears (10% of their study). Biological survival calculations provide a constraint on the reliability of estimated apparent survival from mark and recapture models. Previous research demonstrated that modeled apparent survival dramatically underestimates true biological survival.
Additional Supporting Evidence for Petitioning a USGS investigation
Whether or not reduced Arctic sea ice is the result of natural variability or rising CO2, reduced sea ice benefits the Arctic ecosystem. As discussed in Why Less Summer Ice Increases Polar Bear Populations, evidence and theory unequivocally demonstrates that less ice allows more sunshine for plankton to photosynthesize, causing marine productivity to increase 30% this decade (i.e. Arrigo 2015). Increased marine productivity then reverberates throughout the entire Arctic food chain benefitting cod that are fed on by seals that are fed on by bears. Furthermore all observations have determined that thinner sea ice benefits ringed seals, the polar bears main prey item. Contrary to alarming assertions, less sea ice has generated a more robust food chain!
In a recently published United States Geological Survey (USGS) article, Rode et al (2015) Increased Land Use by Chukchi Sea Polar Bears in Relation to Changing Sea Ice Conditions, researchers tracked radio-collared bears in the Chukchi Sea region and analyzed how much time bears spent on land versus sea ice for the months of August to October. Then they compared that behavior between the 1986–1995 period to 2008–2013. As should be expected with less sea ice, bears naturally spent more time on land. However despite theoretical assertions that less sea ice causes polar bears to suffer “nutritional deprivation”, these researchers observed that a
This confirmed an earlier study during that same time period concluding, “body condition was maintained or improved when sea ice declined”.
“lack of a change in the body condition and reproduction of Chukchi Sea polar bears during the time period of this study suggest that Chukchi Sea polar bears either come onshore with sufficient body fat or they are finding sufficient food resources on land (marine or terrestrial) to offset increased durations on land.”
This confirmed an earlier study during that same time period concluding, “body condition was maintained or improved when sea ice declined”.
In 2007 the 2nd greatest decrease in Arctic sea ice was observed in the waters surrounding Wrangel Island in the Chukchi Sea. That summer researchers likewise observed greater numbers of polar bears on the island. However again contradicting the “less‑ice‑means‑starving‑bears” theory, there were no signs of increased nutritional stress. Quite the opposite! Researchers determined that only less than 5% of the Wrangel Island bears were skinny or very skinny and that compared very favorably to their previous designations of the 7 to 15% skinny bears observed in years with heavier ice. Furthermore researchers determined that not only did 29% of all bears look “normal”, the remaining 66% were fat or very fat. Those polar bear experts wrote,
“Under certain circumstances, such as were observed on Wrangel Island in 2007, resources available in coastal ecosystems may be so abundant that polar bears are able to feed on them more successfully than while hunting on the sea ice.”
Wrangel Island equally illustrates Rode (2015)’s alternative explanation for finding healthy polar bears on land: bears can find sufficient food resources on land to supplement their diet after ringed seals leave the ice.” In the essay Has David Attenborough Become A Propaganda Mouthpiece Promoting Climate Fear? I provided links to published accounts from past centuries and earlier BBC videos demonstrating that polar bears throughout the Chukchi Sea commonly hunt walrus on land; a fact that Attenborough distorted into a cinematic illusion misrepresenting a natural behavior as a function of catastrophic climate change. There is a long list of observations of bears on land actively hunting walruses, reindeer and fish, foraging on berries or scavenging whale carcasses. Although there has been a hypothetical debate on whether or not such supplemental diets could provide the appropriate calories to maintain polar bears’ body condition, based on observations, most bears are doing just fine during years with reduced sea ice.
So why is it suggested that less sea ice reduces polar bears access to food? The short answer is the politics of the “climate wars”. For centuries walruses and polar bears have been observed on land despite much heavier Arctic sea ice during the Little Ice Age. However in the past decade there is a widespread attempt in the media to characterize observations of walruses and bears on land as a “perversion” caused by less sea ice from rising CO2. Skinny injured bears absurdly become media icons of climate change. Yet there is a multitude of peer-reviewed evidence (i.e. McKay 2008, Fisher 2006) that bears and walruses are well adapted to thrive in the extensive periods of reduced Arctic sea ice that were much less than today and persisted throughout the last 10,000 years of the Holocene.
Nearly every alarmist publication that asserts less sea ice causes polar bears to suffer from nutritional stress references as “proof” a 1999 paper by Ian Stirling showing body condition of bears in the western Hudson Bay declined from the 1980s to 1997. However, as seen in the graph below, since 1997 western Hudson Bay polar bears’ body condition has been improving surpassing levels observed in the1980s despite, or because of, years of reduced sea ice. The unpublished improvements of polar bear body condition during the 2000s corresponds well with published reports that since the heavy ice years of the early 1990s reduced ringed seal body condition and reproduction, ringed seal pups tripled during subsequent lighter ice years of the 2000s. However Nicholas Lunn of Environment Canada, has yet to publish that data, while Lunn and other PBSG researchers continue to reference only older zombie pre‑1997 data in assessments as recently as 2014. Publication bias that fails to report positive changes has been a disturbing phenomenon observed elsewhere by authors making catastrophic climate assertions (here and here). Dr. Susan Crockford has also highlighted Lunn’s penchant for deceptive reporting here as he attempts to downplay a recent survey that reports increasing bear populations in the Hudson Bay area.
The recent assessment submitted to the International Union for the Conservation of Nature argued a “reduction in mean global population size greater than 30%” by mid‑century. In contrast all polar bear populations have increased after imposing hunting regulation in the late 60s and 70s. Despite a decadal trend of declining sea ice only 3 of 19 populations are now reported to be declining and uniquely only the Southern Beaufort Sea population is attributed to climate change. The Baffin Bay population has declined due to increased hunting by Greenlanders, and declines in the Kane Basin are attributed to low seal populations due to thick multiyear ice. Of the 7 sub‑populations for which there was comparative data presented in the IUCN’s report, four sub‑populations (Foxe Basin, Gulf of Boothia, Davis Strait, Northern Beaufort) have shown increasing populations. Two subpopulations (Western and Southern Hudson Bay) have shown no significant population change (Stapelton 2014).
Only the Southern Beaufort Sea population suggests a dramatic loss of polar bears, yet before the heavy springtime ice in 2005 there was little sign of reduced body condition. A 2007 USGS study reported that between 1982 and 2006, 95% of the bears in the Beaufort Sea region, exhibited body conditions that were stable or improving. Adult female bears that represented about 34% of all captures exhibited improved body condition. All other categories of bears showed no trend in body condition except for sub-adult males that comprised a mere 5% of the individuals examined. Stable and/or improving body condition again is evidence that the lack of summer sea ice has no detrimental effect on the body condition of polar bears. Nonetheless a co-author of that 2007 study, USGS’ Eric Regehr, used the same data to proclaim in a 2010 paper, “evidence suggests that polar bears in the southern Beaufort Sea are under increasing nutritional stress. From 1982 to 2006, body size and body condition for most sex and age classes were positively correlated with the availability of sea ice habitat, and exhibited a statistically significant decline during this period.”
It is well documented that the Arctic undergoes periodic events producing heavy springtime sea ice that reduces local ringed seal populations in various locations. Ian Stirling co-authored a paper reporting, “heavy ice reduces the availability of low consolidated ridges and refrozen leads with accompanying snowdrifts typically used by ringed seals for birth and haul-out lairs.” He observed in 2005 and 2006, “Hunting success of polar bears (Ursus maritimus) seeking seals was low despite extensive searching for prey.” The most recent paper by USGS researchers Bromaghin 2014 (and discussed here) acknowledges the decline in seal reproduction, yet they never acknowledge that it was a result of a cyclic increase in thick spring ice. As spring ice conditions have now returned to normal, seal ovulation rates also returned to normal, approaching 100%, and the Southern Beaufort bear population is now increasing. Yet because the USGS researchers continue to assert population declines are due to less summer ice and CO2 climate change, they conclude,
“For reasons that are not clear, survival of adults and cubs began to improve in 2007.”
But the reasons are not unknown! The USGS simply refuses to acknowledge global warming and lost summer sea ice has not produced any catastrophic change for polar in the recent past. And the prediction of a 30% decline is a myth that they choose to perpetuate.
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