Saturday, 1 October 2011

Globe's species may number just two million

Far fewer species live on earth than previously thought, and all 2 million are likely to have been discovered by the end of the century, a New Zealand scientist has told an international conference.

Auckland University Associate Professor Mark Costello told the World Conference on Marine Biodiversity last night that previous work on how many species existed had overestimated the numbers.

Speculation has generated estimates that vary by tens of millions, with a recent United States study putting the figure at more than 8 million.

However, in a new paper by Dr Costello and scientists at Trinity College Dublin, the scientists concluded there were likely to be just 1.8 million to 2 million species on Earth. He told The Dominion Post it was the lowest estimate in a "long, long time", but had positive consequences.

"There are always those rare things that will keep being discovered for centuries. But we should get most of the job done in the next 50 or 60 years."

Dr Costello acknowledged the estimate would be considered as low because of the high number of new species being discovered.

"But there has never been so many scientists in the world and people all over the world exploring. This is really the golden age of discovery on planet Earth."

The scientists had adjusted the rate of discovery to reflect the high number of people now involved in such work, and that had led to the new estimate.

The consequences held exciting prospects, Dr Costello said.

"The discovery and description of new species is essential if we are to protect them."

People often despaired that it would be impossible to describe all of Earth's species before they became extinct, but such thinking was based on significant overestimations of the number of species and the rate of extinction.

Dr Costello and the study's authors concluded about 16 per cent, or 0.3 million, of the world's species were marine – significantly fewer than previously thought.

They predict 24 to 31 per cent more marine species, and 21 to 29 per cent more terrestrial species, remain to be discovered.

National Institute of Water and Atmospheric Research principal scientist Dennis Gordon said Dr Costello's argument was convincing if only non-bacterial life was considered. However, though there was a large-enough pool of people able to recognise and describe new species, the work was poorly funded in New Zealand.

Scientists knew of about 46,000 described species in New Zealand's land, sea, and freshwater environments, with a further 8000 undescribed species in museum collections. There were perhaps another 50,000 undiscovered species.

On average, fewer than 200 new species were described each year for New Zealand. Internationally, about 18,000 species were described each year.

Kiran Chug
- The Dominion Post

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