1. 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
9th March 2009
Polar bears of western Hudson Bay and climate change 1

2. Polar 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
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)
Significance to Inuit people
Significance as species to the world
Population stresses have been observed
- Stirling suggested that this is due to increase in spring temperatures
9h March 2009
Polar bears of western Hudson Bay and climate change 3

4. Cause: Discussion points An earlier break-up of Hundson Bay ice
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“
Most cited bears: Southern Hudson Bay polar bear–1 of 14 populations found in Canada-reaches farther south
Polar bears and shrinking ice habitat: used to argue severity of climate change and global warming to the general public
Nonclimatic causes
9h March 2009
Polar bears of western Hudson Bay and climate change 4

5. Polar bears of western Hudson Bay and climate change
Nonclimatic causes
Human-polar bear interactions in Western Hudson Bay
Scientific research
Tourism
Polar Bear Alert System
Since 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
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. Decline has been constant! (Dyck et al.)
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 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. Polar bears of western Hudson Bay and climate change
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): increasing trend (F = 4.16, p = 0.06, r2 = 0.23) not significant
2. Lunn et al. (1997a), 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
- Interannual temperatures vary too much, and this makes it difficult to establish a long term trend, specially because we are considering a short period of time .
- Trend determination is highly sensitive to the time interval considered.
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
Temperature considered forApril, May and June
Dotted line
No statistically significant warming trend can be confirmed for the period considered (1932 to 2002).
Thus, the hypothesis that a warming trend is the principal causative agent for the supposed earlier spring melt and later fall freeze of the sea-ice around WH cannot be confirmed.
Because is not statistically significant different from 0, it can not be assumed that anthropogenic are forcing the trend.
Dashed line
Data agree with Stirling 1999
However when a longer period (until 2002) is considered the trends fails to persist
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
They examine variations of T with the AO (Artic Circulation Oscillation Index). AO -> the dominant pattern of non-seasonal sea-level pressure variations north of 20N latitude, and it is characterized by pressure anomalies of one sign in the Arctic with the opposite anomalies centered about 37-45N.
AO index -> A low (negative) AO value represents higher-than-normal Arctic atmospheric pressure, less cold polar stratosphere and weak subpolar A storm or wind coming from the west.
Temperature and AO (Artic Circulation Oscillation Index) are strongly correlated.
such a complex physical picture connecting oceanic and atmospheric processes with sea-ice variability is dramatically different from Stirling et al. (1999)’s suggestion in which warm spring air temperature is considered to be the ultimate cause for the earlier spring sea-ice break-up4 and poorer conditions of polar bears.
AO index -> potential to understand trophic relation is artic systems, for example high AO values (colder T), were associated with a decrease in plant growth and in reindeer population growth rate. Could be due to bottom-top approach, and then a top-bottom effect due to higher density of reindeer populations too dense, that further lower the plant population
- 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.
Models do not support the disappearance of Polar Bear as a species, specially because even in the worst scenarios the Hudson Bay remain covered by ice in part of the years. Bears are already adapted to have ice-free habitats, because the bay is always ice free in this time of the year. Several trends that contradict CO2 scenarios have been observed: ice thickening, lower Temperatures
Historical records should be further explored, specially in the late 18th century and early 19th century where are clear indications of a climate change in Hudson Bay from temperate to artic conditions.
9h March 2009
Polar bears of western Hudson Bay and climate change 13

14. Polar bears of western Hudson Bay and climate change
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”
- Improved understanding of polar bear resiliency and adaptive strategy to climatic changes must consider human–bear interactions, natural population dynamics, and the dominant components of variability of the Arctic ice, ocean and atmosphere that operate naturally on decadal to multidecadal timescales
Because of this complex situations Polar Bear shouldn’t be considered as the ideal indicators of climatic warming.
Everything for the bear. The comprehensive understanding of the situation will result in more sounding management decisions.
There is no reason to alert the public about an inminent extintion of polar bears when the models are full of uncertainties.
9th March 2009
Polar bears of western Hudson Bay and climate change 14

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

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