Tag Archives: habitat

Arctic sea ice habitat for polar bears is like a big pond that dries up partially in summer

What’s a good analogy for sea ice as essential polar bear habitat? Biologist Andrew Derocher claims that the soil in a forest is appropriate, because without the soil you can’t have the forest ecosystem. However, that’s a specious comparison because the amount of soil in a forest does not change markedly with the seasons the way that Arctic sea ice does.

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A much better analogy is a big pond that dries up a bit every summer. The amount of habitat available to sustain aquatic plants, amphibians and insects is reduced in the dry season but many species have special adaptations for surviving reduced water availability. For the rest of the year, however, the pond provides an abundant and non-limiting habitat for all the creatures and plants that live there.

Beaver pond USFWS

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Sea ice is critical habitat for polar bears from late fall through late spring only

Sea ice is said to be “an essential habitat for polar bears” but that’s an overly simplistic advocacy meme as ridiculous as the “no sea ice, no polar bears” message with which the public is constantly bombarded. Polar bears require sea ice from late fall to late spring only: from early summer to mid-fall, sea ice is optional. Historical evidence of polar bears that spent 5 months on land during the summer of 1874 proves an extended stay ashore is a natural response of polar bears to natural summer ice retreat, not a consequence of recent human-caused global warming. Sea ice is a seasonal requirement for polar bears: it’s not necessary year round.

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[This PBI newsletter from 2011 repeats this meme and Andrew Derocher’s recent tweet conveys a similar message (“Sea ice loss = habitat loss for polar bears”)]

As long as sea ice is available from late fall through late spring (December to early June) and accompanied by abundant seal prey (sometimes it isn’t, see Derocher and Stirling 1995; Stirling 2002; Stirling et al. 1981, 1982, 1984), polar bears can survive a complete or nearly complete fast from June to late November (and pregnant females from June to early April the following year). That’s the beauty of their Arctic adaptation: fat deposited in early spring allows polar bears to survive an extraordinary fast whether they spend the time on land or sea ice.

Young and very old bears, as well as sick and injured ones, are the exception: these bears often come ashore in poor condition and end up dying of starvation — as a much-publicized bear on Baffin Island who likely had a form of cancer did last summer (Crockford 2018). Competition with bigger, stronger bears means these bears can’t keep what they are able to kill and they are most often the bears who cause problems. Starvation is the leading natural cause of death for polar bears because if they cannot put on the fat they need in spring, they will not survive the low food months of summer and winter, whether they are on land or out on the sea ice (Amstrup 2003). Continue reading

Just look at what the ‘global heat wave’ is doing to polar bear sea ice habitat!

According to the Guardian (9 July 2018), there is a “global heat wave” going on right now.

In Siberia, the heat is supposedly “completely unprecedented” and will surely (we are told) impact Arctic sea ice — the habitat of the iconic polar bear.  Yet a comparison of previous years shows little to no impact on sea ice: there is more ice present than there was in 2007.

Polar Bear Breaks Ice

Said The Guardian:

“But though we cannot say definitively that the current heatwave is caused by carbon emissions, it fits the pattern of long-term changes that we call climate. It is part of a global phenomenon, even if not the most important part. The really significant change is happening in eastern Siberia at the moment, where a completely unprecedented heatwave is warming that Arctic coastline, with consequences that are unpredictable in detail but surely bad on a large scale.” [my bold]

The heat — which some folks admit they not only expect during this season called summer but anticipate with joy — has been around since late June, with several locales outside Siberia affected, including southern Ontario, Quebec, Los Angeles CA, Britan, many locations in the eastern USA, Europe.

With so many locations across the Northern Hemisphere experiencing very hot weather over the last few weeks (maybe record-breaking, maybe not), let’s take a look at what all that heat is doing to Arctic sea ice compared to previous years.
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Low Bering Sea ice mostly due to south winds, no data on an impact for polar bears

Sea ice in the Bering Sea this winter was said to be the lowest since the 1850s, largely driven by persistent winds from the south rather than the usual north winds although warm Pacific water was a factor early in the season (AIRC 2018). But what, if any, impact is this surprisingly low winter and spring ice cover likely to have on Chukchi Sea polar bear health and survival?

Rode and Regehr 2010_Chukchi_report2010_Fig1_triplets_labelled

In fact, research on Chukchi Sea polar bears has included so few examples of individuals utilizing the Bering Sea in winter (Jan-March) and early spring (April-May) that any conclusions regarding an impact from this year’s sea ice conditions are likely to be invalid. In short, we don’t know what will happen since it has not happened before within living memory; the opinions of polar bear specialists must be taken with a grain of salt because so many of their previous assumptions have turned out to be wrong (Crockford 2017a,b, 2018), see here, here, and here. Seals, walrus and polar bears are much more flexible and resilent to changes in habitat conditions than most modern biologists give them credit for and consequently, it will be fascinating to see how the ice will change over the coming months and how the animals will respond.

Sea ice extent 2018 March average NSIDC

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Winter polar bear sea ice habitat by early March 2018 varied little from 2006 or 2017

Here’s a polar bear habitat update for early March: some folks are wringing their hands over the relatively extent of ice this season but ice maps show that as far as polar bear habitat is concerned, conditions are not materially different this year from what they were in 2006 or 2017. There is still plenty of late winter sea ice for polar bears needing a platform from which to hunt Arctic seals, which in some areas will have already begun giving birth to their fat furry pups (harp seals first, other species later).

The MASIE map for 5 March 2018 (Day 64) shows ice extent at 14.5 mkm2:

masie_all_zoom_4km 2018 March 5

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Experts talk of their bleak future, W Hudson Bay polar bears get earliest freezeup in decades

It seems that Churchill residents and visitors woke up this morning to find most local polar bears had left to go hunting — on the sea ice that supposedly doesn’t exist. Right in the middle of the Polar Bear Week campaign devised by Polar Bears International to drum up donation dollars and public sympathy for polar bear conservation!

Polar bear on the sea ice_Churchill_8 Nov 2017_Explore dot org cam my photo 2Frigid temperatures and north winds last night helped the process along, but this early freeze-up has been in the works for almost a week. From what I can ascertain, it appeared the only bears around onshore today were a mother with her young cub moving out towards the ice (females with cubs are usually the last to move offshore, probably to reduce the risk of encounters with adult males who might kill the cubs).

Tundra Buggy cams at Explore.org have been showing markedly fewer bears today and those that have been seen were on the ice (see above and below) or heading out to it.

The chart below is for yesterday (7 November), before the cold and north winds hit the region. It shows the concentration of ice that’s >15 cm thick.

Hudson Bay North 2017 concentration Nov 7

The chart for 8 November is below, after the storm.

Hudson Bay North daily ice concentration 2017_Nov 8

This is ice thick and extensive enough for polar bears to go hunting. Some bears almost certainly left shore yesterday, with the rest following quickly on their heals today. There are sure to be some stragglers left ashore that will leave over the next few days but the fact remains: there is sea ice to be had for those polar bear willing to start hunting.

Watch polar bear on the WHB sea ice below (screen caps below – and one above – were taken the afternoon of 8 November, from the Tundra Buggy Cam live feed near Churchill).

Polar bear on the sea ice_Churchill_8 Nov 2017_Explore dot org cam my photo 3

Keep in mind that in the 1980s, bears left for the ice on 8 November, on average. That means we’re back to a 1980s freeze-up scenario, at least for this year.

Funny how no one bothered to mention the potential for an early freeze-up to the media last week, when scientist were so eager to talk about the imminent demise of WHB bears. And funny that Polar Bears International hasn’t tweeted a word today about the famous Churchill bears having enough sea ice to go hunting, smack in the middle of Polar Bear Week.

Yes, the “Save Our Sea Ice” PBI rallying cry sounds a bit hollow with sea ice as far as the eye can see off Churchill today. But will anyone in the mainstream media point out the irony?

See charts below for years back to 2004, on this date (2005 missing for some reason), to compare to the above 8 November image (2004 is as far back as the archive goes).

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Svalbard polar bear habitat higher than average – here’s what that looks like

Polar bear habitat around Svalbard in the Barents Sea is currently slightly above average for 23 June 2017: this short post records what that amount of ice looks like according to the Norwegian Ice Service (NIS).

Svalbard ice extent 2017 June 23_NIS from archive

Compare to 2015 at the same date, the year that the last polar bear count was conducted for the Svalbard region, when many cubs were seen and the bears were reported in excellent condition:

Svalbard ice extent 2015 June 23_NIS from archive

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