polar bear assessment

polar bear in press

people kinda expected a listing higher than special concern

the press argued that canada’s system for assessment (COSEWIC) was flawed with no expert opinion…

they claimed old data, etc

polar bear designations

special concern in Canada based on our pop only (no pop decline overall), quantitative criteria

threatened in US based on global population, qualitative def

vulnerable from IUCN, based on global (=threatened for COSEWIC), quantitative criteria

why didnt COSEWIC assess sub popns of polar bears as different DUs?

it didnt meet the criteria:

no genetic, behavioural, life history differences

no range disjunction

occupy a single ecozone

critera for COSEWIC listing for polar bear

B - EO is too large, no severe fragmentation

D - number of individuals too large

A,C - rely on population decline which is based in generation length (not shown to decline with either generation length)

E - used data from Bayesian Analysis, would have supported threatened criteria but there was only one expert on the case and he said he was just modelling things so there wasn’t enough justification

COSEWIC generation length

generation time = mean age of reproductive individuals

ex polar bears had 12 years, for 3 generations it was 36 years

note a longer generation time results in a larger decline

IUCN generation length

generation = age at first reproduction + half the length of the reproductive period in a complete life cycle

so for polar bears ex. 5 (even tho this is very low, only 26% are) + 20/2 = 15 years, for 3 generations is 45 years

to use this definition they need to be able to support it, age 5 was hardly supported - note a longer generation time results in a larger decline

so why did the IUCN rank higher?

they can basically say whatever they want with no legal backing, no legal repurcussions

vs cosewic who is legally bound, the govt has to be able to support the decisions they make / the assessment