In light of recent news, the topic of the KT extinction seemed fitting. It has been announced that we have lost around 60% of animal populations since 1970. Whilst the loss of species abundance and biodiversity are different, this figure of 60% is reminiscent of biodiversity loss resulting from the last mass extinction, a meteorite impact responsible for wiping out the dinosaurs 66Ma, where an estimated 57-83% of species went extinct.
The Cretaceous was unlike today, although the continents were migrating towards their present day positions. The climate was very warm (with reptiles being able to exist above the arctic circle) and sea levels were at the highest they have ever been with most of Europe being entirely submerged and a vast seaway present across America, effectively dividing it in two (this site has some excellent palaeogeographic reconstructions).
The Cretaceous marked the end of the Mesozoic, an era dominated by dinosaurs. However, it is becoming increasingly apparent that the End-Cretaceous was undergoing a gradual decline in biodiversity in the millennia leading up to the extinction. The bolide impact was only one of many factors responsible for this massive drop in biodiversity, other factors included continental drift and disruption of thermohaline circulation, gradual cooling and intensive volcanism.
Modern rates of biodiversity loss are higher than at any point in recent history and has gone beyond the threshold level of "safe levels" of biodiversity loss. This raises and interesting, if frightening, thought: could human activity eventually have the same effect on global biodiversity loss as volcanism, a 10-15km asteroid impact and continental drift had over many thousands of years at the End-Cretaceous, and are we heading for our sixth mass extinction?
Comments