Page 675 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Chapter 19 ecosystem essentials 639
visualanalysis 19 Declining food, climate change impacts, and animal stress
Declining food resources due to a loss of sea ice in an Arctic food web. A male polar bear (Ursus mari- timus) walks between the ocean and a walrus (Odo- benus rosmarus) haul along the ice-free shore of Phippsøya (Phipps Island), Arctic Ocean, in 2013. Sea ice, including the multiyear ice preferred by polar bears in their hunt for seals, dominated this same scene in the early 2000s. Without sea ice for their hunting platform, polar bears must forage for food on land, searching for bird eggs, injured wal- ruses or seals, and even consuming kelp. Mean- while, walruses feed on clams in the shallows near land, brushing aside sand and sediment with their whiskers, pulling the clam meat into their mouths with a powerful sucking action. These walrus males weigh more than 1000 kg each. The hungry bear keeps its distance, instinctively avoiding exposure to the dangerous walrus tusks.
1. Describe the conflict in the bear between an instinctual fear of the tusks and the hunger he is experiencing. What do you think happened at this scene? [See answer below]
2. Where would this polar bear normally feed, if sea-ice conditions were similar to the year 2000 and earlier?
3. How are climate-change impacts impacting the different polar bear and the walrus food webs?
[What happened: after 20 minutes of the wal- ruses looking but not moving, and the polar bear blocking their escape route to the sea, sniffing the air, and inspecting the haul out, the polar bear left the scene, still hungry.]
[Bobbé Christopherson.]