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.
