What is mass extinction and are we facing a sixth one?
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The definition of a mass extinction
Extinction is a part of life, and animals and plants disappear all the time. About 98% of all the organisms that have ever existed on our planet are now extinct.
When a species goes extinct, its role in the ecosystem is usually filled by new species, or other existing ones. Earth’s ‘normal’ extinction rate is often thought to be somewhere between 0.1 and 1 species per 10,000 species per 100 years. This is known as the background rate of extinction.
A mass extinction event is when species vanish much faster than they are replaced. This is usually defined as about 75% of the world’s species being lost in a ‘short’ amount of geological time - less than 2.8 million years.
Katie Collins, Curator of Benthic molluscs at the [Natural History] Museum says, ‘It’s difficult to identify when a mass extinction may have started and ended. However, there are five big events that we know of, where extinction was much higher than normal background rate, and these ...
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