Unsurprisingly warmer
conditions in the Arctic allows for an increase in the number of polar bears,
surely by making it easier to go after seals.
The only place that they could experience negative population pressure
would be South Hudson Bay and that appears to be minor.
Importantly the screams
of environmentalists and their doubtful science are clearly countered in the
best way possible and that is by a visibly thriving population.
The climate is warmer
in the Arctic but this only makes more sea ice accessible for exploitation by
the seals and that allows an increase in Polar Bear populations. That should have been obvious from the
beginning long before they went after endangered species designation.
Global population of
polar bears has increased by 2,650-5,700 since 2001
Posted
on July 15, 2013 |
The
official population estimates generated by the IUCN Polar Bear Specialist Group
(PBSG) give the impression that the global total of polar bears has not changed
appreciably since 2001:
2001
PBSG
report
21,500-25,000
2005
PBSG report
20,000-25,000
2009
PBSG
report
20,000-25,000
2013
PBSG website
20,000-25,000
However,
some accounting changes were done between 2001 and 2009 (the latest report
available) that mean a net increase in numbers had to have taken place (see
summary map below and previous post here.Note this is a different issue than the misleading
PBSG website graphic discussed here).
And
while it is true that population “estimates” are just that — rather broad
estimates rather than precise counts — it is also true that nowhere do the
PBSG explain how these dropped figures and other adjustments were accounted for
in the estimated totals.
The
simple details of these changes are laid out below, in as few words as I could
manage, to help you understand how this was done and the magnitude of the
effect. It’s a short read — see what you think.
Polar
bear subpopulations as defined by the PBSG: Top, in the 2001 report; Bottom,
2009 report. Map courtesy PBSG, with a few labels added and the subpopulations
identified where “accounting” changes or adjustments to estimates took place.
SB, Southern Beaufort; NB, Northern Beaufort; VM, Viscount Melville; MC, M’Clintock Channel; LS, Lancaster Sound; GB, Gulf of Boothia; NW, Norwegian Bay; KB, Kane Basin; WH, Western Hudson Bay. Click to enlarge.
Changes
in the early 2000s
Between 2001 and 2005 the ‘Queen Elizabeth Islands’ region in northern-most Canada (see map above) was dropped altogether as a distinct subpopulation (along with its estimated 200 bears) and the tentative total of 2,000 bears estimated for ‘East Greenland’ was also dropped (from both minimum and maximum portions of the “21,500-25,000″ range).
In
addition, about 1,000 was added to the minimum and about 1,000 subtracted
from the maximum totals because a new, more accurate estimate for the
Barents Sea became available in 2004, replacing the guess of “2,000-5,000” used
in the 2001 report.1
That
means between 2001 and 2005, due to accounting and ‘upgrade’ changes only,
a total of 1,200 bears was removed from the minimum portion of the global
estimate and 3,200 removed from the maximum portion of the global estimate, changes
that had nothing to do with documented declines in subpopulations. These
changes were all the result of differences in the way the data was presented
(or not).
As
a consequence, if the total population of polar bears had otherwise been
unchanged or declined in the early 2000s, the total in 2005 should
have been 20,300-21,800 — or less. However, the official total for
2005 was given as “20,000-25,000” – reflecting a reduction of 1,500 in the minimum portion
of the estimate only (i.e. down from “21,500-25,000” in 2001).
This
means there must have been a net increase of 300-3,200 bears (average
1,750) among the remaining subpopulations during the early 2000s. A comparison
of the tables suggests these increases occurred in the Lancaster Sound, Gulf of
Boothia and Davis Strait subpopulations.
Changes
in the late 2000s
In 2009, the tentative total of 2,000 bears estimated for the ‘Chukchi Sea’ subpopulation was dropped – from both the minimum and maximum total estimates – because it was deemed not accurate enough: “2,000″ became “zero,” even though bears are well known there (see previous posts here and here).
In
addition, in the 2009 report, the Barents Sea subpopulation estimate was
changed: given as “2,997 (2,299-4,116)” in 2005, based on studies completed in
2004, it was adjusted down to “2,650 (1,900-3,600)” in 2009, based on the
same 2004 data. This ‘adjustment’ dropped another 350 bears from the minimum
total2 and a whopping 500 bears from the maximum total (numbers rounded to
keep things simple 2) that again,had nothing to do with a documented
change in the number of bears in the Barents Sea but rather, a change in
accounting.
But
did the total estimate of polar bears worldwide in 2009 drop from
“20,000-25,000” to “17,650-22,500” to reflect the removal of the Chukchi
estimate and the adjustment in the Barents Sea figure? No, it did not.
[Now,
the Barents Sea estimate is not the only subpopulation estimate that was
'adjusted' from one number to another based on the same survey data, but since
we are tracking the Barents Sea figures from a "guess" in the 2001
report to a scientific estimate in 2009, it's important to include this final
adjustment]
As
a consequence, because the global estimate did not change between 2005 and
2009, there must have been another net increase of 2,350-2,500
polar bears among the remaining subpopulations in the late 2000s.
In
summary, in order for the worldwide estimate of polar bears to have remained
virtually unchanged since 2001, the global population must have increased
by 2,650-5,700 bears (average 4,175) between 2001 and 2013. These
increases did not off-set the slight declines in other subpopulations, as the
unchanging totals imply, but were in addition to them.
In
other words, it appears that the global population of polar bears could not
have remained stable since 2001 – it had to have increased by an average of
almost 4,200 bears!
Footnotes
1. The Barents Sea subpopulation was roughly estimated to have been “2,000-5000” in 2001. This means that of the “20,000-25,000” total estimate, 2,000 of the “20,000” minimum came from the Barents Sea and 5,000 of the “25,000” maximum came from the Barents Sea. However, the contribution of Barents Sea bears to the total changed in 2005 because a new, more accurate estimate became available (stated as “2,997 average, range of 2,299-4,116”). No other subpopulation estimate, except the Barents Sea, changed from a tentative, ‘educated guess’ to a science-based estimate between 2001 and 2012, so I contend it is valid to include this as an “accounting change.”
2.
In 2005, as far as I can tell 2,997 of the “20,000” total minimum estimate came
from the Barents Sea, and 4,116 of the “25,000” maximum estimate came from the
Barents Sea (that’s because in contrast to previous years, in 2005 the total
estimate range (i.e. “20,000-25,000”) appears to be the total of the average estimate for
each subpopulation (rather than the minimum) and the total of the maximumestimate for
each subpopulation, see previous post here.
References
2001 PBSG report:
Lunn, N.J., Schliebe, S., and Born, E.W. (eds.). 2002. Polar Bears: Proceedings of the 13th working meeting of the IUCN/SSC Polar Bear Specialists Group, 23-28 June , 2001, Nuuk, Greenland. Gland, Switzerland and Cambridge UK, IUCN.
2005
PBSG report:
Aars, J., Lunn, N. J. and Derocher, A.E. (eds.) 2006. Polar Bears: Proceedings of the 14th Working Meeting of the IUCN/SSC Polar Bear Specialist Group, 20-24 June 2005, Seattle, Washington, USA. Occasional Paper of the IUCN Species Survival Commission 32. IUCN, Gland, Switzerland and Cambridge, UK.
2009
PBSG report:
Obbard, M.E., Theimann, G.W., Peacock, E. and DeBryn, T.D. (eds.) 2010. Polar Bears: Proceedings of the 15th meeting of the Polar Bear Specialists Group IUCN/SSC, 29 June-3 July, 2009, Copenhagen, Denmark. Gland, Switzerland and Cambridge, UK.
1 comment:
This is awesome!
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