Geoscience Reference
In-Depth Information
Table A1.
(continued)
Node
Name
Node Title
Node Description
States
U
Reproduction
The sum of trends in numbers of cubs produced and the effect of retreating sea ice on
the ability of females to reach traditional denning areas.
increased
same_as_now
decreased
V1
Cub production
per event
This node describes the number of cubs produced per denning attempt.
fewer_than_now
same_as_now
more_than_now
l
Juvenile
Survival
Annual natural survival rate of cubs and yearlings. Note that this is conditional on sur-
vival of the mother. This is the survival rate for juveniles that would occur in absence
of hunting or other anthropogenic factors. Those anthropogenic factors that would
influence survival are included in node F.
increase
no_change
decrease
l1
Adult Female
Survival
Annual natural survival rate of sexually mature females. This is the survival rate for
adult females that would occur in absence of hunting or other anthropogenic factors.
Those anthropogenic factors that would influence survival are included in node F.
increase
no_change
decrease
k
Adult Body
Condition
Body mass index or other indicator of ability of bears to secure resources. Our analysis
suggests body stature has been declining in the SBS and is inversely correlated with
ice extent. Also recent analyses indicate that body condition may soon be an important
predictor of survival of polar bears in ShB.
increase
same_as_now
decrease
Summary Nodes - USFWS Listing Factors
b
F2
Factor A.
habitat Threats
This node summarizes the combined information about changes in habitat quantity
and quality. It approximately reflects factor A of the proposal to list polar bears as
threatened.
improvement
no_effect
minor_restriction
major_restriction
A1
Factor B.
Overutilization
This node approximates the FWS listing factor B. It includes the combination of hunt-
ing (harvest), take for scientific purposes, and take for zoos. It also includes mortalities
from bear-human interactions etc. brought in from factor E. These all are factors which
serve to modify the population changes that would be brought about without the direct
local interference of humans.
fewer
same_as_now
more
A4
Factor C.
Disease,
predation
This node expresses probability of changing vulnerability of polar bears to diseases
and parasites, and to potential increases of intraspecific predation/cannibalism.
same_as_now
worse
A6
Factor E. Other
factors (natural
or man-made)
This node approximately corresponds to factor E of the listing proposal. It includes
factors (other than the changes in sea ice quality and quantity) which may affect habitat
suitability for polar bears. Also, its effects can be directly on population dynamics fea-
tures. hence, it applies directly to both the habitat and population sides of our network.
Included here are effects of a variety of contaminants, including: petroleum hydrocar-
bons, persistent organic pollutants, and metals. Although we do not know much quanti-
tatively about effects of these contaminants at the population level, we know qualita-
tively that effects on immune systems and steroid levels etc. will ultimately have such
effects. We also know that oil spills will have immediate and dire effects.
It also includes effects of human activities and developments which may directly affect
habitat quality, including: shipping and transportation activities, habitat change, noise,
spills, ballast discharge, and ecotourism. This includes disturbance but not direct killing
of bears by humans as a result of DlP cases (direct killing is included under node A1).
I viewed human disturbances as the most predictable in their negative effects until pol-
lution levels reached their greatly elevated stage at which time, their import to future
populations was judged to be great.
improvement
no_effect
minor_restriction
major_restriction
Descriptive (Disconnected) Nodes
c
Q
Time Period
The states for this node correspond to years −10 (historic), 0 (now), 25 (early century),
50 (mid century), 75 (late century), and 95 (end of century).
historic (1985-1995)
now (1996-2006)
early century
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