Researcher leads precise, innovative effort to count species on Earth

University of Hawaiʻi at Mānoa
Posted: Aug 23, 2011

Dr. Camilo Mora
Dr. Camilo Mora
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.
Announced today by Census of Marine Life scientists, 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. Furthermore, the study published today 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.
Said lead author and researcher Dr. Camilo Mora of the University of Hawai‘i at Mānoa’s Geography Department, “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. Many species may vanish before we even know of their existence, of their unique niche and function in ecosystems, and of their potential contribution to improved human well-being.”
Added co-author Boris Worm of Dalhousie University in Halifax, Canada, “This work deduces the most basic number needed to describe our living biosphere. 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? It is the same with biodiversity. Humanity has committed itself to saving species from extinction, but until now we have had little real idea of even how many there are.”
Drs. Mora and Worm, together with the latter’s Dalhousie colleagues Derek P. Tittensor, Sina Adl and Alastair G.B. Simpson, 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.
Based on current costs and requirements, the study suggests that describing all remaining species using traditional approaches could require up to 1,200 years of work by more than 300,000 taxonomists at an approximate cost of $364 billion. Fortunately, new techniques such as DNA barcoding are radically reducing the cost and time involved in new species identification.
Concluded Dr. Mora: “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. Renewed interest in further exploration and taxonomy could allow us to fully answer this most basic question: What lives on Earth?”
The paper is available for full media view at