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John Garcia Luisa Ricaurte

Polar bears of western Hudson Bay and climate change: Are warming spring air temperatures the ‘‘ultimate’’survival control factor?. John Garcia Luisa Ricaurte. 9 th March 2009. Polar bears of western Hudson Bay and climate change. 1.

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John Garcia Luisa Ricaurte

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  1. Polar bears of western Hudson Bay and climate change: Are warming spring air temperatures the ‘‘ultimate’’survival control factor? John Garcia Luisa Ricaurte 9th March 2009 Polar bears of western Hudson Bay and climate change 1

  2. 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 Polar bears of western Hudson Bay and climate change 2

  3. 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 Polar bears of western Hudson Bay and climate change 3

  4. Discussion points Population stresses have been observed: decreases of reproduction, subadult survival, body mass of some of those bears Cause: • An earlier break-up of Hundson Bay ice • and 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 Nonclimatic causes 9h March 2009 Polar bears of western Hudson Bay and climate change 4

  5. Nonclimatic causes Human-polar bear interactions in Western Hudson Bay • 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 • Scientific research • Tourism • Polar Bear Alert System • 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 Polar bears of western Hudson Bay and climate change 5

  6. Data are not clearly reported and conflicting information exists WH polar bear population between around 1100 bears WH most stable population 2772 captured bears, 145/ year 1100 recaptured bears (52-90%) Handled bears 9th March 2009 Polar bears of western Hudson Bay and climate change 6

  7. Dyck et al., 2008. 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. 9th March 2009 Polar bears of western Hudson Bay and climate change 7

  8. Food availability and competition “Incoherence between the long-term data on population estimates and the predictions made by the authors” 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) - 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 Polar bears of western Hudson Bay and climate change 8

  9. 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 South Hudson polar bear 9th March 2009 Polar bears of western Hudson Bay and climate change 9

  10. Air temperature and climate variability around Hudson Bay Source of Data: NASA and U.S. National Climatic Data Center 9h March 2009 Polar bears of western Hudson Bay and climate change 10

  11. Air temperature and climate variability around Hudson Bay Source of Data: NASA and U.S. National Climatic Data Center 9h March 2009 Polar bears of western Hudson Bay and climate change 11

  12. Temperature and Artic Circulation Oscillation Index - 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. 9h March 2009 Polar bears of western Hudson Bay and climate change 12

  13. Conclusions from Dyck et al., on Stirling et al. 1999 • 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. 9h March 2009 Polar bears of western Hudson Bay and climate change 13

  14. 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 likelystress 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 Polar bears of western Hudson Bay and climate change 14

  15. QUESTIONS??? 9th March 2009 Polar bears of western Hudson Bay and climate change 15

  16. 9th March 2009 Polar bears of western Hudson Bay and climate change 16

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