As the world gets hotter, migratory animals move north

Reports are piling up of odd animal sightings in northern regions: salmon swimming through the Bering Strait between Alaska and Russia; birds like the Cape May warbler moving from U.S. spruce forests to cooler Canadian climes; a fish usually found off the coasts of Africa or southern Europe swimming in a Norwegian fjord; Texas political hatchet men passing pork-filled legislation in Washington, D.C. Scientists are increasingly worried about the impacts such species shifts may have on delicately balanced ecosystems. Those wandering warblers eat a lot of spruce budworm caterpillars, for example, and warbler-free forests will be more vulnerable to wood-drying infestation and subsequent fires. Though many observers link the migrations to global warming, not everyone is convinced. “If you want to measure temperatures, you use a thermometer, not a bird,” said noted climate-change skeptic Fred Singer. “Birds have all sorts of reasons for moving north, south, sideways, or whatever.” Ah, those whimsical birds.