How many species are there on Earth and in the Ocean?

Scientists have recently discovered the most precise estimate ever offered on the total number of species on Earth: 8.7 million. The calculation is based on novel, validated analytical technique that enabled them to identify 6.5 million species found on land and 2.2 million dwelling in the ocean. The study was conducted by Census of Marine Life scientists and published by PLoS Biology, a peer-reviewed science journal that publishes new and research.

Key Points:

Up until now, the number of species on Earth was said to fall somewhere between 3 million and 100 million. The best approximation of Earth’s species total was based on the educated guesses and opinions of experts, who variously pegged the figure in a range from 3 to 100 million -- wildly differing numbers questioned because there is no way to validate them.
Dr. Camilo Mora and Dr. Boris Worm, together with 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).
Jesse Ausubel, vice-president of the Alfred P. Sloan Foundation and co-founder of the Census of Marine Life notes the enigma of why so much diversity exists, saying the answer may lie in the notions that nature fills every niche and that rare species are poised to benefit from a change of conditions.

Pull Quotes:

“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 Census of Marine Life 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.” -Dr. Camilo Mora, lead author, researcher at Dalhousie University in Halifax and the University of Hawaii.
“This work deduces the most basic number needed to describe our living biosphere. If we did not know -- even by an order of magnitude (1 million? 10 million? 100 million?) -- the number of people in a nation, how would we plan for the future?”-Dr. Boris Worm, coauthor, assistant professor in the Department of Biology, Dalhousie University in Halifax.
“It is a remarkable testament to humanity’s narcissism that we know the number of books in the U.S. Library of Congress on 1 February 2011 was 22,194,656, but cannot tell you -- to within an order-of-magnitude -- how many distinct species of plants and animals we share our world with.” -Lord Robert May, commentator and former president of the UK's Royal Society.
“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?” -Dr. Camilo Mora, lead author, researcher at Dalhousie University in Halifax and the University of Hawaii.

Images:


Thalurania nigricapilla Download Hi-Res	Harpaphe haydeniana Download Hi-Res	Aleutihenricia federi Download Hi-Res	Kingdom diagram Download Hi-Res