Mass extinctions
(a) Mass extinction and the regaining of biodiversity. Fossil evidence indicates that there have been several mass extinction events in the past. Following each mass extinction event, biodiversity has been regained slowly due to speciation of survivors. The difficulties in estimating past and current species extinction rates. The extinction of mega fauna correlated with the spread of humans. The escalating rate of ecosystem degradation caused by humans is causing the rate of species extinction to be much higher than the natural background rate.
