Geography 2156B Lecture Notes - Lecture 2: Pleistocene Megafauna, Cambrian Explosion, Defaunation

• School: Western University
• Department: Geography
• Course: Geography 2156B
• Professor: tony weis

Document Summary

Short period of time in which large share of species go extinct. "background rate" at which species evolve and die off. "spasm" rapid pace in relatively short period u the cambrian explosion ~540m yrs ago rise of most major animal phyla. Precipitous declines from hunting: passenger pigeons, blue whale, fin whale, gray whale (n. atlantic: extinct) Global homogenization of plants & animals: spread of non-native species around the world, humanity using 25%-40% of the planet s net primary production (hanpp) Un milennium ecosystem assessment (2005: ~expected extinctions, over 100yrs: 32% of fish; 12% of birds; 25% of mammals, present: ~1000x "background rate"; next future, ~10,000x.