Mass extinctions

  • For millions of years, the average rate of extinction was one species per century. Most of the extinctions since prehistoric times were in the last 300 years. Of those, over half took place in the last 50 years. Of those, over half took place in the last 10 years. There are currently more than 1000 different species of plants and animals becoming extinct every year. Mark Cawardine, in Adams, 241
  • There have been five major extinction events in known natural history where species diversity plummeted in a short period of time – called the "Big Five". We are currently in a period of possibly similar extinction event proportions, likely caused by humans. Theorists are already terming this the "Sixth Extinction." Kolbert, 3
  • The change in temperature projected by 2100 is ~as big as the temperature swings of the ice ages, but at least 10 times faster. In order for organisms to survive, they will have to adapt an order of magnitude faster than they have before. Kolbert, 161-162
  • Species-area relationship: S = cA^z where z is less than 1. S=number of species, A=area, c=some constant (asymptotal graph). As conditions change, directly or indirectly by climate, a species's ability to adapt or move (incl. dispersal over generations) to stay in favorable conditions determines its survival. Based on this, about 24% (pretty definitely this order of magnitude) of species will be committed to extinction by 2050 if current climate change rates continue. This puts the current extinction at a "lesser" extinction level compared to the earth's history, not quite on par with a big five extinction event Kolbert, 166-168
  • Salmon as particular case study: 5 major factors influencing are harvest (overfishing), hydropower (dams), habitat, hatcheries Montgomery, 5
  • Salmon runs in the Pacific Northwest are stronger when the ocean's surface climate is cooler. This happens with a periodicity (opposite Alaska's) every 25 to 30 years. Cooler in 2001ish Montgomery, 43

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