Roughly 90 per cent of the species in the world have yet to be discovered, described and catalogued by humans, according to a new scientific study.

The study by Canadian researchers estimated the number of species at 8.7 million. The scientists developed a new method of estimating the global total, and published their findings in the journal PLoS Biology on Tuesday.

“We are astonishingly ignorant about how many species are alive on earth today, and even more ignorant about how many we can lose yet still maintain ecosystem services that humanity ultimately depends upon,” Oxford University zoologist Robert May wrote in a separate paper for the same edition.

Previous estimates of the world’s species ranged from 3 million to 100 million.

The study conducted at Dalhousie University of Halifax estimated that 86 per cent of all terrestrial species and 91 per cent of all marine species have yet to be catalogued.

It estimated about 7.8 million species of animals, 298,000 of plants, 611,000 of fungi, 36,400 of protozoa and 27,500 of chromists - which include algae and water moulds.

It said only about 7 per cent of fungi and 12 per cent of animals have been identified, compared with 72 per cent of plants.

The methodology excluded microorganisms and viruses, and carried a standard error margin of 1.3 million. The study estimated there are 2.2 million marine species, with the rest being terrestrial.

Marine biologist Boris Worm, one of the co—authors, said Earth is a system with millions of vital parts, many of which regularly disappear.

“If you think of the planet as a life-support system for our species, you want to look at how complex that life-support system is,” he said.

“We’re tinkering with that machine because we’re throwing out parts all the time.”

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