CFE agenda 121216 - Laserfiche WebLink

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Revised draft (BK Dec 5, 2016 consequences was that reef building stopped, resulting in reef gaps in the geologic record. Such gaps mark at least four mass extinctions. The largest mass extinctions are: end of Permian (252 Ma), end of Triassic (200 Ma), and end of Cretaceous (66 Ma). They coincided with the three largest regional outpourings of flood basalt. The Permian extinction was the biggest in history wiping out an estimated 90% of all life and lasted no more than 200,000 years, a geologic instant. The subsequent recovery of biodiversity took about 50 million years. Global warming and mass extinction were already underway when an asteroid impact dramatically ended the Cretaceous and the dinosaurs, paving the way for mammals to take over and ultimately leading to the origin of Homo sapiens. What emerges from the geologic record is that mass extinction has occurred multiple times and is likely to occur again. In fact, extinction is underway now and has been termed the Anthropocene extinction, beginning when human activity started to impact global earth systems. Only the starting point is in question. Many point to the start of the industrial revolution. Others would start the clock earlier during the Pleistocene (Ice Age). Humans caused the extinction of the Ice Age megafauna and Neanderthals in a geologic instant but it was too gradual to be perceived by the perpetrators. Right now humans are causing extinction. The contemporary extinction rate greatly exceeds the naturally occurring background rate. Whether humankind continues on a path to mass extinction or one similar to the many lesser extinction events that punctuated the Phanerozoic remains to be seen. Homo sapiens as the agent of extinction risks being one of its victims.