A new paper on Baffin Bay polar bears reports data on body condition and litter sizes collected as part of a major study of the region completed in 2013 compared to sea ice declines since the 1990s; based on a computer model, the authors predict that in 37 years time (if sea ice declines continuously), the incidence of twin litters could “largely disappear.” However, no decline in population numbers was predicted and a critical caveat acknowledges that factors other than changes in sea ice could have affected the body condition and litter size data the authors analyzed, which means the conclusions are scientifically inconclusive.
The last (2013) polar bear population survey of Baffin Bay (SWG 2016) generated an estimate of almost 3,000 (2,826; range 2,059-3,593), which means that regardless of some slight changes in body condition and litter size over the last two decades (which may or may not have been caused by loss of sea ice), there are currently a lot of bears in Baffin Bay.
Posted in Conservation Status, Life History, Sea ice habitat
Tagged baffin bay, body condition, causation, correlation, extinction, fatness, Greenland, litter size, NASA, polar bear, sea ice, weight
Results from spring Norwegian fieldwork in the Svalbard region of the Barents Sea are in and they show that despite having to deal with the most extreme loss of summer sea ice in the Arctic, polar bears in this region continue to thrive.
Svalbard polar bear territory (managed by Norway) includes sea ice to the Russian boarder to the east as well as the area around the Svalbard archipelago: the map below is from Aars et al. 2017.
Observations were collected around Svalbard by a team lead by Jon Aars and Magnus Andersen of the Norwegian Polar Institute between March and May this year, and posted online 4 June 2019. Kudos to them for making their on-going observations and analysis available, in a timely manner for all to see.
Note that Svalbard is the western half of the ‘Barents Sea’ polar bear subpopulation: in recent years, most of the region’s polar bears have been living around Franz Josef Land in the eastern (Russian) sector where Norwegian researchers are not permitted to work.
Posted in Conservation Status, Population, Sea ice habitat
Tagged Barents Sea, condition, data, litter size, males, Norway, number of cubs, observations, polar bear, sea ice, Svalbard
Last week, the Norwegian Polar Institute updated their online data collected for the Svalbard area to include 2017 and 2018 — fall sea ice data and spring polar bear data. Older data for comparison go back to 1993 for polar bears and 1979 for sea ice, showing little to no impact of the reduced ice present since 2016 in late spring through fall.
Here’s what the introduction says, in part [my bold]:
“…The polar bear habitat is changing rapidly, and the Polar Basin could be ice-free in summer within a few years. Gaining access to preferred denning areas and their favourite prey, ringed seals, depends on good sea ice conditions at the right time and place. The population probably increased considerably during the years after hunting was banned in 1973, and new knowledge indicates that the population hasn’t been reduced the last 10-15 years, in spite of a large reduction in available sea ice in the same period.”
See Aars et al. 2017 for details on the 2015 Svalbard polar bear population count, keeping in mind that the subpopulation region is called “Barents Sea” for a reason: only a few hundred individuals currently stick close to Svalbard year round while most Barents Sea bears inhabit the pack ice around Franz Josef Land to the east (Aars et al. 2009; Crockford 2017, 2018).
Posted in Advocacy, Conservation Status, Sea ice habitat
Tagged Barents Sea, body condition, decline, denning, Derocher, Franz Josef Land, litter size, mothers with cubs, polar bear, population, sea ice, Svalbard
What exactly are Western Hudson Bay (WHB) polar bear researchers hiding? Since 2004, research on the body condition and cub production of Western Hudson Bay (WHB) polar bears has been carried out but none of the results of these mark-recapture studies have been made public.
The researchers all claim that WHB polar bears are struggling to survive because of recent sea ice changes but won’t release the 10 years worth of updated information they possess on the bears or the sea ice.
Posted in Advocacy, Conservation Status, Population, Sea ice habitat
Tagged Amstrup, body condition, climate change, cub mortality, Derocher, global warming, invasive research, litter size, Lunn, mark-recapture, misinformation, photo ops, polar bear, polar bear survival, polar bear week, Polar Bears International, population estimate, propaganda, vital rates, western hudson bay
So far, I’ve not discussed the Barents Sea subpopulation in very much detail, except in comparison to other groups. For example, the Barents is considered to be the same type of sea ice “ecoregion” as the Chukchi Sea and the Southern Beaufort (discussed here). Previous studies on the Barents Sea polar bear population (Derocher 2005) indicate it may have recovered from extreme levels of overhunting (discussed here) and had stabilized, or was increasing very slowly, as early as 2002 (discussed here) — similar to what has happened in Davis Strait (discussed here).
Figure 1. Polar bear subpopulations, with the Barents Sea region highlighted; map courtesy the IUCN Polar Bear Specialist Group (PBSG), extra labels added.
The most recent Barents Sea population estimate was done in 2004 (2,650; range ~1900-3600), based on an aerial survey (Aars et al. 2009). Aerial surveys are the only practical method of establishing population counts in regions like this where many bears never set foot on land. The previous estimate for the Barents (1982) was “2,000-5,000” but its accuracy was considered “poor” (discussed here).
The IUCN Polar Bear Specialist Group (PBSG), in their most recent report, lists the Barents Sea population as “data deficient” for status, current trend and estimated risk of decline within 10 years (Obbard et al. 2010:62, Table 1) and the “notes” for this entry say:
“Population estimate is based on a new aerial survey. There was likely an increase in the subpopulation size after 1973 until recently. Current growth trend is unknown.”
This 2004 estimate is now almost a decade old and potentially no longer an accurate representation of what’s happening in the Barents Sea. The most up-to-date information has not yet been published but it is available online. It’s eye-opening to say the least, if only that it appears to be yet another example of a polar bear population that is so far not showing signs of being harmed by sea ice declines, as I’ve discussed before (here).
[Update October 15, 2013: I’ve simplified the text discussion and figure regarding the Aars and Andersen denning study from the original posted]
Posted in Conservation Status, Life History, Population, Sea ice habitat
Tagged aerial survey, Barents Sea, body condition, Derocher, ecoregrions, Environmental Monitoring of Svalbard and Jan Mayen, Jon Aars, litter size, Magnus Andersen, maternity dens, Mauritzen, MOSJ, number of cubs, Olga Pavlova, population size, pregnant females, reproduction, sea ice, Sebastian Gerland, Svalbard
One aspect of the recently published study on Chukchi Sea polar bears (Rode et al.2014 [now in print]
2013; see here and here) has not been stressed enough: their finding that the differences in overall condition between bears in the Chukchi and Southern Beaufort Seas came down to disparities in spring feeding opportunities and therefore, the condition of spring sea ice.
The fact that spring — not summer — is the most critical period for polar bears is something I’ve pointed out before (see here and here, for example) but it’s worth repeating at this time of year, when all eyes are on the annual ice minimum. It is often treated as a given that the decline in extent of summer sea ice in the Arctic since 1979 has been detrimental to polar bears. However, this is an assumption that we can now say is not supported by scientific evidence (see summary of that evidence here).
The results published by Rode et al. (2014
2013) not only add further support to the conclusion that declines in summer sea ice have not harmed polar bears, but should put the matter to rest – unless new evidence to the contrary is produced.
Chukchi bears, the report tells us, had more food available in the spring than Southern Beaufort bears (see map below) and this was the primary reason that bears were doing very well in the Chukchi and not quite as well in the Southern Beaufort. And because the polar bears for this study were captured and measured in mid-March to early May, from 2008 to 2011, they reflect spring-time conditions for 2008-2011 as well as year-round conditions from 2007 through 2010.
This means that the annual low ice extent for 2007 (record-breaking at the time), in the fall before this study began, had no discernible negative effect on either Chukchi or Southern Beaufort polar bears – and neither did similarly low annual minimums in two of the three remaining years of the study (Fig 1).
Posted in Conservation Status, Life History, Sea ice habitat
Tagged annual summer minimum, arctic sea ice, Beaufort Sea, body condition, Cherry, Chukchi, declining sea ice, Eastern Beaufort, good news, heavy sea ice, Hudson Bay, ice-free Arctic, litter size, loss of summer ice, Pilfold, polar bear, record low, Regehr, ringed seals, Rode, sea ice extent, Southern Beaufort, Stirling, summer ice minimum, summer sea ice, thick spring ice