A new report has found that nearly 90 per cent of Australia's mammals and reptiles are found nowhere else in the world.

The audit by Australian scientists, titled Numbers of Living Species in Australia and the World, found there are nearly 1.9 million known animal and plant species on the planet.

Environment Minister Peter Garrett says the review includes the discovery of a number of new species unique to Australia.

"We know that Australia is a mega-diverse continent, but this is absolutely confirmation of that," he said.

"I guess the other thing is it shows we are actually discovering new species, with some 48 new reptiles, eight new mammals, 1,100 flowering plants and nearly 1,000 mites, spiders and scorpions also being discovered."

The report found that only about a quarter of Australia's flora and fauna has been discovered and named.

It also found that in the last three years, 18,000 new species were discovered each year. About three-quarters of those were invertebrates.

Mr Garrett says the audit is a crucial benchmark.

"It will be a really important contribution in the global fight to save biodiversity, so I am delighted it's happening in Australia," he said.

Details of the official audit will be unveiled by Mr Garrett today at the Australian Institute of Marine Science, south of Townsville.