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Nature is believed to kill off around one in every ten million animals each year.

At this rate, for every 10,000 species of mammal on the planet, an entire species will have become extinct in the last millennium.

But now that humans are on the scene, species are dying off as much as 1,000 times faster than they did 60 million years ago, according to a new US study.

Nature is believed to kill off around one in every ten million animals each year. Pictured is a Sumatran orangutan twenty-four year old female, named Ratna, playing with her female baby, named Global. The Sumatran oranguatan are critically endangered

The study at Brown University analysed genetic variation in the family trees of a number of plant and animal species to look at how they spread over time. It also looked at fossil records.

Previous estimates looked only at fossils, which the authors said made previous estimates on extinction rates inaccurate as it didn't consider the exact species.

Scientists calculated a 'normal background rate' of extinction of 0.1 extinctions per million species per year.

Past estimates for the normal background rate was 10 yearly extinctions for 10 million species.

The new study found the pre-human extinction rate was 10 times lower than scientists had believed, which means that the current level is 10 times worse.

A map of the distribution of threatened bird species in the Americas, showing their concentration in the coastal forests of Brazil and in the northern Andes. Red means more species

Future extinction rates are likely to be 10,000 times higher than nature's rates of extinction. Pictured is a golden snub-nosed monkey in China. The species is on the endangered list

'This reinforces the urgency to conserve what is left and to try to reduce our impacts. It was very, very different before humans entered the scene,' said Jurriaan de Vos, a Brown University Phd researcher.

And they believe future extinction rates are likely to be 10,000 times higher than nature's rates of extinction.

'It's rather like your bank account on the day you get paid,' said Mr de Vos. 'It gets a burst of funds — akin to new species — that will quickly become extinct as you pay your bills.'

This paper follows a recent one in Science that tracks where species that are threatened or confined to small ranges around the world.

A white-footed sportive lemur in Madagascar (left) and a giant panda (right), both endangered. The main cause of extinctions is thought to be human population growth

In most cases, the main cause of extinctions is human population growth, although the paper also says how humans have been able to promote conservation.

'We've known for 20 years that current rates of species extinctions are exceptionally high,' said Stuart Pimm, president of the conservation nonprofit organisation SavingSpecies.

'This new study comes up with a better estimate of the normal background rate — how fast species would go extinct were it not for human actions. 

'It's lower than we thought, meaning that the current extinction crisis is much worse by comparison.'