Mass extinction? Man may still have time to catalog Earth's species.

The analysis, co-written by Oxford University zoologist Robert May and Nigle Stork at Griffith University in Australia, draws on several recent studies to suggest that cataloging species before they vanish may be more tractable than many believe.

Better scientific housekeeping – settling on one scientific name for an organism (many creatures often had several) has helped lower the estimate of known species from about 1.9 million to 1.5 million, Costello says. Improvements in the methods for estimating Earth's biodiversity have narrowed the range of extant nonbacterial species from between 30 million and 100 million to perhaps 2 million to 8 million, with the team's best estimate at 5 million.

Meanwhile, the pace of discovery has been picking up. Over the past 10 years, an average of 17,500 new species have been described each year, a rate that has reached 18,000 a year since 2006.

It has been difficult to determine the overall global extinction rate for nonbacterial organisms. Some vertebrates have been disappearing at rates comparable to previous mass extinctions, the team notes. But conservation efforts, habitats that may be degraded or fragmented, but not destroyed, and the adaptability of some organisms to farmland or human-managed forests, could well be slowing the planet's overall pace of extinctions, the team suggests.

For all the efforts to improve estimates of the planet's overall species count, that number remains highly uncertain, cautions Andrew Hamilton, a biologist and executive director of academic innovation at the University of Houston.

"The fact of the matter is we don't know, even within an order of magnitude, how many species there are on the planet," he says.

In the end, however, the numbers may be less important than the analysis's overall message that while formidable, the cataloging task is attainable within a reasonable period of time, given money and creative ways to enlist more hands and eyes to the task, Dr. Hamilton says.

For instance, with the range of technologies available – from vast online data bases to smart phones that can take a high-resolution picture; stamp it with date, time, and a GPS location; then upload it to a central repository – the discovery effort can enlist dedicated amateurs for some aspects, researchers say.

One popular approach is known as a BioBlitz – a 24-hour assault on a particular patch of land by professionals and volunteers to record as many organisms as possible in that location.

The American Museum of Natural History's Novacek recalls a BioBlitz the museum and other groups sponsored in Central Park in 2003. More than 800 species were identified in the trees, on the ground, and in ponds, with participants discovering a new species of centipede, Novacek says.

The effort represents nothing less than planetary exploration, Hamilton suggests.

"If we organize our workforce efficiently and we treat this like a mission to a little-known planet," it's possible to assemble the catalog of nonbacterial organisms within a generation, Hamilton says.

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