Mass Extinction Events

In this month's focus magazine ( http://www.bbcfocusmagazine.com/ ) there is an article on endangered species and how by the end of the century more than 50% of all species around today could be gone by the end of the century. Within the article it lists the biggest five extinction events in the Earth's history and the remarkable thing is that the K-T event ( http://en.wikipedia.org/wiki/Cretaceous%E2%80%93Tertiary_extinction_event ), which is probably the most famous mass extinction, didn't actually kill off as much of life as you might think. It wiped out the dinosaurs (with the exception of birds) but compared to the other mass extinction events it was actually relatively tame.

The banner in the article states the following:

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ORDOVICIAN-SILURIAN
-440 Million Years Ago-
The second largest extinction. Up to 85% of species vanish probably due to global cooling.

LATE DEVONIAN
-364 Million Years Ago-
20% of all species, mostly marine based, die out in a massive environmental shift. The root cause is not known.

PERMIAN-TRIASSIC
-251 Million Years Ago-
The biggest extinction event in history - the 'Great Dying'. A combination of natural disasters kills off 96% of marine species and 70% of land species.

TRIASSIC-JURASSIC
-199-214 Million Years Ago-
Massive volcanic eruptions are the prime suspect in the demise of 23% of all species. It vacated ecological niches to be exploited by dinosaurs.

CRETACEOUS-TERTIARY (K-T)
-65 Million Years Ago-
A meteor collides with Earth. The effects of the impact probably killed off 16% of marine species and 18% of land animals - including the dinosaurs.

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Now if the scientists are correct then this century will see the 3rd largest extinction level event in the Earth's history; and it is primarily humankind's fault. Humans ARE an extinction level event! Makes you think doesn't it?