Reposted from Dr. Susan Crockford’s Polar Bear Science
Posted on July eight, 2020 |
This up to date weblog submit of mine from final 12 months is as pertinent now because it was then: it’s a fully-referenced rebuttal to the deceptive ‘details’ so usually introduced this time of 12 months to help the notion that polar bears are being harmed attributable to lack of summer time sea ice. Polar Bears Worldwide developed ‘Arctic Sea Ice Day’ (15 July) to advertise their skewed interpretation of polar bear science on the top of the Arctic soften season. This 12 months I’ve add a ‘Polar Bears and the Arctic Meals Chain‘ graphic, which readers are free to obtain and share. For additional data, see “The Polar Bear Disaster That By no means Occurred“.
Summer time sea ice loss is lastly ramping up: first 12 months is disappearing, because it has executed yearly since ice got here to the Arctic hundreds of thousands of years in the past. However important misconceptions, fallacies, and disinformation abound relating to Arctic sea ice and polar bear survival. Forward of Arctic Sea Ice Day (15 July), listed below are 10 fallacies that lecturers and oldsters particularly have to learn about.
As all the time, please contact me if you need to look at any of the references included on this submit. These references are what make my efforts totally different from the activist group Polar Bears Worldwide. PBI nearly by no means present references throughout the content material it gives, together with materials it presents as ‘instructional’. Hyperlinks to earlier posts of mine that present expanded explanations, photographs, and extra references are additionally supplied.
Sea ice background: extent during the last 12 months
Summer time sea ice minimal 2019 (from NSIDC):
Winter sea ice most 2020:
Sea ice at 7 July 2019: early summer time extent
Although 2019 had the 2nd lowest extent for the month of June since 1979, by the tip of June 2020 (as was additionally the case in 2019), there was nonetheless ice adjoining to all main polar bear denning areas throughout the Arctic (see chart beneath).
In lots of areas – together with Western Hudson Bay, Wrangel Island, and Franz Josef Land – pregnant females that can give delivery on land in December come ashore in summer time and keep till their new child cubs are sufficiently old to return with them to the ice the next spring. See Andersen et al. 2012; Ferguson et al. 2000; Garner et al. 1994; Jonkel et al. 1978; Harington 1968; Kochnev 2018; Kolenosky and Prevett 1983; Larsen 1985; Olson et al. 2017; Richardson et al. 2005; Stirling and Andriashek 1992.
Ten fallacies and disinformation about sea ice
1. ‘Sea ice is to the Arctic as soil is to a forest‘. False: this all-or-nothing analogy is a specious comparability. In reality, Arctic sea ice is sort of a large wetland pond that dries up a bit each summer time, the place the quantity of habitat accessible to maintain aquatic vegetation, amphibians and bugs is diminished however doesn’t disappear utterly. Wetland species are tailored to this habitat: they can survive the diminished water availability within the dry season as a result of it occurs yearly. Equally, sea ice will all the time reform within the winter and keep till spring. Throughout the two million or so years that ice has shaped within the Arctic, there has all the time been ice within the winter and spring (even in hotter Interglacials than this one). Furthermore, I’m not conscious of a single trendy local weather mannequin that predicts winter ice will fail to develop over the following 80 years or so. See Amstrup et al. 2007; Durner et al. 2009; Gibbard et al. 2007; Polak et al. 2010; Stroeve et al. 2007.
2. Polar bears want summer time sea ice to outlive. False: polar bears which have fed adequately on younger seals within the early spring can reside off their fats for 5 months or extra till the autumn, whether or not they spend the summer time on land or the Arctic pack ice. Polar bears seldom catch seals in the summertime as a result of solely predator-savvy grownup seals can be found and holes within the pack ice enable the seals many alternatives to flee (see the BBC video beneath). Polar bears and Arctic seals really require sea ice from late fall via early spring solely. See Crockford 2017, 2019; Hammill and Smith 1991:132; Obbard et al. 2016; Pilfold et al. 2016; Stirling 1974; Stirling and Øritsland 1995; Whiteman et al. 2015.
Three. Ice algae is the premise for all Arctic life. Solely partially true as a result of plankton additionally thrives in open water through the Arctic summer time, which finally gives meals for the fish species that ringed and bearded seals eat through the summer time, which fattens the seals up earlier than the lengthy Arctic winter (because the graphic beneath exhibits).
Current analysis has proven that much less ice in summer time has improved ringed and bearded seal well being and survival over circumstances that existed within the 1980s (when there was a shorter ice-free season and fewer fish to eat): as a consequence, ample seal populations have been a boon for the polar bears that rely upon them for meals in early spring. For instance, regardless of dwelling with essentially the most profound decline of summer time sea ice within the Arctic polar bears within the Barents Sea round Svalbard are thriving, as are Chukchi Sea polar bears – each opposite to predictions made in 2007 that resulted in polar bears being declared ‘threatened’ with extinction below the Endangered Species Act. See Aars 2018; Aars et al. 2017; Amstrup et al. 2007; Arrigo and van Dijken 2015; Crawford and Quakenbush 2013; Crawford et al. 2015; Crockford 2017, 2019; Frey et al. 2018; Kovacs et al. 2016; Lippold et al. 2019; Lowry 2016; Regehr et al. 2018; Rode and Regehr 2010; Rode et al. 2013, 2014, 2015, 2018.
four. Open water in early spring in addition to summer time ice soften since 1979 are unnatural and detrimental to polar bear survival. False: melting ice is a traditional a part of the seasonal adjustments within the Arctic. Within the winter and spring, numerous areas of open water seem as a result of wind and currents rearrange the pack ice – this isn’t soften, however relatively regular polynya formation and growth. Polynyas and widening shore leads present a helpful mixture of ice resting platform and nutrient-laden open water that draws Arctic seals and gives wonderful looking alternatives for polar bears. The map beneath exhibits Canadian polynyas and shore leads recognized within the 1970s: comparable patches of open water routinely develop in spring off jap Greenland and alongside the Russian coast of the Arctic Ocean. See Dunbar 1981; Grenfell and Maykut 1977; Hare and Montgomery 1949; Smith and Rigby 1981; Stirling and Cleator 1981; Stirling et al. 1981, 1993.
Recurring polynyas and shore leads in Canada recognized within the 1970s. From Smith and Rigby 1981
5. Local weather fashions do a great job of predicting future polar bear habitat. False: My current ebook, The Polar Bear Disaster That By no means Occurred, explains that the virtually 50% decline in summer time sea ice that was not anticipated till 2050 truly arrived in 2007, the place it has been ever since (but polar bears are thriving). That’s a very dangerous monitor document of sea ice prediction. Additionally, opposite to predictions made by local weather modelers, first 12 months ice has already changed a lot of the multi-year ice within the southern and jap portion of the Canadian Arctic Archipelago, to the good thing about polar bears. See additionally ACIA 2005; Crockford 2017, 2019; Durner et al. 2009; Hamilton et al. 2014; Heide-Jorgensen et al. 2012; Perovich et al. 2018; Stern and Laidre 2016; Stroeve et al. 2007; SWG 2016; Wang and Overland 2012.
Simplified predictions vs. observations as much as 2007 supplied by Stroeve et al. 2007 (courtesy Wikimedia). Sea ice hit an excellent decrease extent in 2012 and all years since then have been beneath predicted ranges.
6. Sea ice is getting thinner and that’s an issue for polar bears. False: First 12 months ice (lower than about 2 metres thick) is one of the best behavior for polar bears as a result of it is usually one of the best habitat for Arctic seals. Very thick multi-year ice that has been changed by first 12 months ice that melts utterly each summer time creates extra good habitat for seals and bears within the spring, after they want it essentially the most. This has occurred particularly within the southern and jap parts of the Canadian Arctic Archipelago (see ice chart beneath from Sept 2016). Due to such adjustments in ice thickness, the inhabitants of polar bears in Kane Basin (off NW Greenland) has greater than doubled because the late 1990s and numbers of bears in M’Clintock Channel (within the SE Archipelago) have reportedly additionally elevated. See Atwood et al. 2016; Durner et al. 2009; Lang et al. 2017; Stirling et al. 1993; SWG 2016.
7. Polar bears in Western and Southern Hudson Bay are most prone to extinction attributable to international warming. False: Ice decline in Hudson Bay has been among the many lowest throughout the Arctic. Sea ice decline in Hudson Bay (see graphs beneath) has been lower than someday per 12 months since 1979 in comparison with greater than four days per 12 months within the Barents Sea. Hudson Bay ice decline additionally uniquely occurred as a sudden step-change in 1998: there has not been a gradual and regular decline. Since 1998, the ice-free season in Western Hudson Bay has been about Three weeks longer general than it was within the 1980s however has not turn out to be any longer during the last 22 years regardless of declines in whole Arctic sea ice extent or elevated carbon dioxide emissions. Ice protection over Hudson Bay on the finish of June in 2020 was as excessive as final 12 months, offering good sea ice circumstances for WH and SH polar bears for the final 5 years not less than. See Castro de la Guardia et al. 2017; Regehr et al. 2016.
Lack of summer time sea ice per 12 months, 1979-2014. From Regehr et al. 2016.
eight. Breakup of sea ice in Western Hudson Bay now happens three weeks sooner than it did within the 1980s. False: Breakup now happens about 2 weeks earlier in summer time than it did within the 1980s. The whole size of the ice-free season is now about Three weeks longer (with numerous year-to-year variation). WH polar bears tagged final 12 months have been nonetheless on the ice on the finish of June 2020. See Castro de la Guardia et al. 2017; Cherry et al. 2013; Lunn et al. 2016; and video beneath, displaying the primary bear noticed off the ice at Cape Churchill, Western Hudson Bay, on 5 July 2019 – fats and wholesome after consuming effectively through the spring:
9. Winter sea ice has been declining since 1979, placing polar bear survival in danger. Solely partially true: whereas sea ice in winter (i.e. March) has been declining step by step since 1979 (see graph beneath from NOAA), there isn’t a proof to recommend this has negatively impacted polar bear well being or survival, because the decline has been fairly minimal. The ocean ice chart in the beginning of this submit exhibits that in 2020 there was loads of ice remaining in March to satisfy the wants of polar bears and their main prey (ringed and bearded seals), regardless of 2019 being the 11th lowest since 1979 (and the very best since 2013).
10. Specialists say that with 19 totally different polar bear subpopulations throughout the Arctic, there are “19 sea ice eventualities enjoying out“ (see additionally right here), implying that is what they predicted all alongside. False: So as to predict the longer term survival of polar bears, biologists on the US Geological Survey in 2007 grouped polar bear subpopulations with comparable sea ice varieties (which they referred to as ‘polar bear ecoregions,’ see map beneath). Their predictions of polar bear survival have been primarily based on assumptions of how the ice in these 4 sea ice areas would change over time (with areas in inexperienced and purple being equally extraordinarily susceptible to results of local weather change). Nevertheless, it seems that there’s way more variation inside and between areas than they anticipated and extra variations in responses to summer time sea ice loss than predicted: opposite to predictions, the Barents Sea has had a far higher decline in summer time ice extent than some other area, and each Western and Southern Hudson Bay have had comparatively little (see #7). See Amstrup et al. 2007; Atwood et al. 2016; Crockford 2017, 2019, 2020; Durner et al. 2009; Lippold et al. 2019; Regehr et al. 2016. My newest ebook, The Polar Bear Disaster That By no means Occurred, explains why this prediction primarily based on sea ice ecoregions failed so miserably.
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