Professor John J. Wiens of the University of Arizona, will focus on how species respond to climate change. If climate change causes conditions to shift outside the climatic niche of a species, then populations must either move, acclimate behaviorally or physiologically, or adapt evolutionarily and shift their climatic niche. Otherwise, the species may go extinct. The discussion will expand on two key issues: (a) how quickly do climatic niches evolve relative to the projected pace of future climate change? (b) what causes species and populations to go extinct as climate changes?