Tag Archives: population decline

Graphing polar bear population estimates over time

I’ve already commented on the 2013 update of polar bear population status released by the IUCN Polar Bear Specialist Group (PBSG).

However, I thought it might be interesting to graph the changes in global population estimates over time (from 1981-2013) — not just the actual estimates from PBSG status tables (with their min/max error ranges) but those totals plus the so-called “inaccurate” estimates that the PBSG have dropped from their accounts in recent (2005-2013) assessments: Chukchi Sea, East Greenland, Queen Elizabeth Islands (now known as the “Arctic Basin”), and Laptev Sea.

In 2001, those “inaccurate” estimates contributed 5,000-5,400 bears to the global total, but now they’re gone — no bears from those regions contribute to the official totals listed on recent PBSG status tables.

Adding those dropped estimates back into the global totals makes it possible to generate a graph in which the global estimates are truly comparable over time.

To see how the dropped estimates influenced the perception of population change over time, I’ve also graphed the estimates given by the PBSG in their status tables. I’ve combined the two into one image (Fig. 1, click to enlarge) to make comparison easy.

UPDATE 5 December 2014: Links to more recent posts relevant to this issue added below. The most recent numbers, added 31 May 2015, are here.

UPDATE 26 March 2019: See “Latest global polar bear abundance ‘best guess’ estimate is 39,000 (26,000-58,000)
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Polar bears at Kaktovik, Alaska not stranded due to retreating ice

“I’ve lived here all my life and there are more bears every year. I read stories about polar bears being on the brink of extinction because of global warming, look out of my window and start to laugh.” Tori Sims, Kaktovik (Mail on Sunday, Sept. 28, 2013).

As you can see, Kaktovik is in the news again. This tiny community sits on the edge of the Beaufort Sea, on Barter Island on the North Slope of Alaska (Fig. 1). It lies within the Southern Beaufort polar bear subpopulation, which has been classified as “declining” by the IUCN Polar Bear Specialist Group (Obbard et al. 2010).

The determination of “declining” was based on a small dip in population numbers between 2001 and 2006 (not statistically significant), plus a decline in body size and condition, and smaller litter sizes documented between 1986 and 2006 (Rode et al. 2010). A new population survey is underway.

Figure 1. Kaktovik, Alaska, from Google maps.

Figure 1. Kaktovik, Alaska, from Google maps. Click to enlarge.

There have been suggestions that bears become “stranded” along the Alaska coast near Kaktovik because of retreating sea ice, and that more bears present in this area in recent years are an indication that they are in trouble due to global warming.

I’ve compiled some quotes, maps, and links to stories, photos and videos about Kaktovik polar bears to show that this claim is false.

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The two faces of polar bear biologists – Zac Unger interviews Amstrup and Stirling

Former firefighter Zac Unger has been in the news quite a lot over the last few months, promoting his new book, “Never Look a Polar Bear in the Eye” (see Zac’s website here, where you’ll find a list of some of the articles he’s written; the Canadian Geographic one is very good (“The truth about polar bears”) and was the one that originally caught my attention in early December 2012. One article that I’ve read is missing from that list, “Are Polar Bears Really Disappearing?” (Wall Street Journal, Feb. 8, 2013). There is a book review in the Winnipeg Free Press here (Feb. 2, 2013) and on climate scientist Judith Curry’s blog (Dec. 21, 2012), and an interview with Globe and Mail columnist Margaret Wente here from Feb. 23, 2013).

I’ve mentioned bits from some of these articles previously: Featured Quote #32 (Feb. 23, 2013) and in my Dec. 16, 2012 post, ‘Species-threatening’ population declines vs. polar bear declines.

In my last post, I promised a follow-up discussion on cannibalism in polar bears, as it has been promoted by polar bear biologists. I recalled a discussion of this by Unger, which I think makes a nice lead-in for my own essay, which I should have up in a few days.

Here is the money quote from Unger (with a link to the NBC interview with Amstrup and Stirling he is talking about). A lengthy excerpt from the article is below, for the context – it’s well worth a read:

[In 2008, after watching polar bear biologist Dr. Steve Amstrup give an interview on NBC News explaining “the evidence behind the decision to list the polar bear as threatened. Evidence like cannibalism.”] “Wait a second. Hadn’t Amstrup just finished telling me that the cannibalism thing was getting too much play by a bloodthirsty media?” Zac Unger, PS Magazine, Dec. 17, 2012 [2:40 min. NBC News video here]

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