polar bears of western hudson bay and climate change: are warming spring air temperatures the...
Post on 19-Dec-2015
214 views
TRANSCRIPT
Polar bears of western Hudson Bay and climate change: Are warming spring air temperatures the ‘‘ultimate’’survival control factor?
John GarciaLuisa Ricaurte
9th March 2009 1Polar bears of western Hudson Bay and climate change
Based on Dyck et al. (2007) Polar bears of western Hudson Bay and climate change: Are warming spring air temperatures the ‘‘ultimate’’ survival control factor? ecological complexity 4:73 – 8 4
Overview:- Introduction- Polar Bears: Food availability,
competition and interactions with human populations.
- Air temperature and climate variability around Hudson Bay
- Extrapolating findings to global population of Polar Bears
- Conclusions- Questions
9h March 2009 2Polar bears of western Hudson Bay and climate change
Polar Bears (Ursus maritimus)
“a multipurpose natural resource”
Charismatic megafauna that symbolize the Artic Traditional role for the Canadian Inuit: spiritual, mystical, cultural Economic role Sport hunting: local communities
“is endangered due to climate change and environmental stress” (Stirling, WWF, Derocher)
or simply “due to unsustainable harvests by human hunters” (Taylor et al., 2005)
9h March 2009 3Polar bears of western Hudson Bay and climate change
9h March 2009 4Polar bears of western Hudson Bay and climate change
Discussion points
An earlier break-up of Hundson Bay iceand Increase of the air temperature in spring
„a long-term warming trend of spring atmospheric temperatures“(Sterling et al.,….)
NOT SHOWN DIRECTLY TO BE THE „ULTIMATE FACTOR“Polar bears and shrinking ice habitat:
used to argue severity of climate change and global warming to the
general public
Most cited bears: Southern Hudson Bay polar bear–1 of 14 populations
found in Canada-reaches farther south
Population stresses have been observed: decreases of reproduction, subadult survival, body mass of some of those bears
Cause:
Nonclimatic causes
Nonclimatic causes
Human-polar bear interactions in Western Hudson Bay
1. Scientific research
2. Tourism
3. Polar Bear Alert System
•Since 1966. Marked 80% of bears. Capturing and handling wildlife repeatedly: effects on females with cubs•Works in spring: high stress-lactation, emerge from dens, end of fasting period
•Since 1980, during the fall, Oct.-Nov., early freezy-up, north migration•Polar bear viewing, short season, intensive, 6000 tourists, 15 tundra vehicles per day•Baiting, harassment and chasing of bears have been documented to occur
•Initiated in 1969, to protect local residents and vice versa•Bears will be deterred, captured, handled or destroyed•up to 2000: 1547 bears have been handled, average of 48 per year
9th March 2009 5Polar bears of western Hudson Bay and climate change
Data are not clearly reported and
conflicting information exists
Handled bears
2772 captured bears, 145/ year1100 recaptured bears (52-90%)
WH polar bear population between around 1100 bears
WH most stable population
9th March 2009 6Polar bears of western Hudson Bay and climate change
Decline of WH Polar bear has accelerated over the
time (Stirling et al.)
Decline has been constant! (Dyck et al.)
Up to 1997 did not change significantly, aprox. 1200
bears
Estimate of WH Bay polar bear. Regehr et al., 2007.
Dyck et al., 2008.
9th March 2009 7Polar bears of western Hudson Bay and climate change
Food availability and competition
1. Derocher and Stirling (1995): 1977-1992 - increasing trend (F = 4.16, p = 0.06, r2 = 0.23) not significant
2. Lunn et al. (1997a), 1984 -1995 - indicate a stable population (F = 0.71, p = 0.42, r2 = 0.07)
3. When both data sets are combined there is a significant increase in the population size (F = 6.40, p = 0.02, r2 = 0.27)
“Incoherence between the long-term data on population estimates and the predictions made by the authors”
- Stirling et al, the data responses reflect density-dependent population control mechanisms- Dyck et al., argue that these responses are typically detected in increasing populations
9th March 2009 8Polar bears of western Hudson Bay and climate change
South Hudson polar bear
Population distribution of Ursus maritimus in the southern HB
„independent populations; Increasing competition; food supply insufficient“Bears have learned to hunt seals during the ice-free period along the shores in
tidal flats
Western Hudson polar bear
9th March 2009 9Polar bears of western Hudson Bay and climate change
Air temperature and climate variability around Hudson Bay
Source of Data: NASA and U.S. National Climatic Data Center
9h March 2009 10Polar bears of western Hudson Bay and climate change
Air temperature and climate variability around Hudson Bay
Source of Data: NASA and U.S. National Climatic Data Center
9h March 2009 11Polar bears of western Hudson Bay and climate change
Temperature and Artic Circulation Oscillation Index
9h March 2009 12Polar bears of western Hudson Bay and climate change
- Strong cooling trend (about 0.4 ºC per decade since 50s)
- Temperature and AO (Artic Circulation Oscillation Index) are strongly correlated
- AO appers to be responsible for the changes in the tickness of sea-ice in the region.
- Because of the sea-ice becomed less thin, the air Tº increased.
Conclusions from Dyck et al., on Stirling et al. 1999
9h March 2009 13Polar bears of western Hudson Bay and climate change
Warming temperatures are the ultimate factor that explain Polar Bear population
conditions status in WH and in the Artic in general – unsupportable! Not scientific
sound.
Models do not support the disappearance of Polar Bear as a species
Uni-dimensional or reductionist thinking – not useful on complex systems!
Polar bear WH is exposed to several environmental perturbations :unknown seal
populations size, competition with other polar bear populations and human
interactions.
Dyck et al, argue:
„global warming may indeed have an effect on the ecology of polar bears, but it must be assessed with all the likely stress factors and their cumulative impacts“
“it needs the combined assessment of both natural and social systems”
“rather the consideration of isolated components”
9th March 2009 14Polar bears of western Hudson Bay and climate change