Andrew Revkin just posted a nice link to a recent response by one of the world's foremost polar bear experts to an attack on global-warming based predictions of polar bear declines. The original critique was written by J. Scott Armstrong, a Professor Marketing at the Wharton School. As I've noted before, Armstrong's paper suffers from a number of pretty significant flaws, not the least of which is its total inversion of the precautionary principle.
In a related story, Andrew also recently wrote about a study on the capacity of polar bears to adapt to global warming by shifting their foraging from seals to snow goose eggs during extended ice-free summers. I've now had a chance to read the full study and, as I suspected, although very interesting, it contains some significant caveats that ought to prevent us from deriving too much hope from the author's conclusions. Key graphs:
Competition could lead to a "tragedy of the commons" situation (Rankin et al. 2007), where individual self-interests degrade a resource the whole group could use. Preliminary simulations indicate that if more than 36% of the nests are depredated the snow goose colony would decline. Both Madsen et al. (1998) and Drent and Prop (2008) indicate that polar bear depredation on Svalbard is sufficient that it is impacting the resident goose populations.
While the energy from snow goose eggs may reduce or delay the immediate impact of climate change on the polar bears of this region, simple extrapolation of the available egg energy values indicate that other food sources will have to play a role if the polar bears are to persist in the long term.
The authors also say that: "It is our view that in monitoring the health of this species, we should pay particular attention to the polar bears' diverse foraging abilities and their attempts to cope with environmental changes. We feel this is a better approach than making predictions based only on their historic behaviors in habitats that are themselves now changing."
While I disagree with this conclusion both as a matter of policy and law, it's only fair to note.