Posted on | August 26, 2011 | Comments Off
There are 8.7 million species on Earth, give or take 1.3 million. That is the new, estimated total number of species on the planet—the most precise calculation ever offered—with 6.5 million species found on land and 2.2 million (about 25 percent of the total) dwelling in ocean depths.
“The question of how many species exist has intrigued scientists for centuries and the answer, coupled with research by others into species’ distribution and abundance, is particularly important now because a host of human activities and influences are accelerating the rate of extinctions,” says lead author and Mānoa Assistant Professor Camilo Mora. “Many species may vanish before we even know of their existence.”
Census of Marine Life scientists say the figure is based on an innovative, validated analytical technique that dramatically narrows the range of previous estimates. Until now, the number of species on Earth was said to fall somewhere between 3 million and 100 million. The study published on Aug. 23 by PLoS Biology says a staggering 86 percent of all species on land and 91 percent of those in the seas have yet to be discovered, described and catalogued.
“This work deduces the most basic number needed to describe our living biosphere,” says co-author Boris Worm of Dalhousie University in Halifax, Canada. “If we did not know—even by an order of magnitude such as 1 million, 10 million, 100 million—the number of people in a nation, how would we plan for the future?”
Mora and colleagues refined the estimated species total to 8.7 million by identifying numerical patterns within the taxonomic classification system (which groups forms of life in a pyramid-like hierarchy, ranked upwards from species to genus, family, order, class, phylum, kingdom and domain). Analyzing the taxonomic clustering of the 1.2 million species today in the Catalogue of Life and the World Register of Marine Species, the researchers discovered reliable numerical relationships between the more complete higher taxonomic levels and the species level.
“With the clock of extinction now ticking faster for many species, I believe speeding the inventory of Earth’s species merits high scientific and societal priority,” says Mora. “Renewed interest in further exploration and taxonomy could allow us to fully answer this most basic question: What lives on Earth?”