More specifically, they suggest an extinction rate of 10 times the background rates.

The extinction rate peaked about a million years before the end of this stage.

He says that the only scientifically observed extinction rate in this century is one species a year.

Without human intervention, he said, the natural extinction rate is about 1 plant species every 1,000 years.

This country is desperately trying to stem the extinction rate of species.

But it's clear there may have been other things going on at the same time that enhanced the extinction rate.

Lower extinction rates lead to more species in the tropics.

One is to show how the damage has moved onto a new scale by comparing past and present extinction rates.

Then repeat the same thing after humans arrived to find an 'artificial' extinction rate.

But today, the extinction rate appears to be anywhere from 100 to 1,000 times greater than that.