Yet to be discovered and cataloged, scientists estimate, are
between 74,000 and 90,000 plant species, some of which may help
increase world food production, according to the PLoS
Biology commentary by Lord Robert May of Oxford. This
wild rice, for example,Oryza
officinalis, photographed in the Philippines, inherently
resists pests and diseases and tolerates extreme environmental
conditions and its genes are used to improve cultivated rice
varieties. Credit: Photo credit required:
Eight million, seven hundred thousand species (give or take 1.3
million).
That is a new, estimated total number of species on Earth -- 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 the 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% of all species on land and 91%
of those in the seas have yet to be discovered, described and
catalogued.
Says lead author Camilo Mora of the University of Hawaii and
Dalhousie University in Halifax, Canada: "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."
"This work deduces the most basic number needed to describe our
living biosphere," says co-author Boris Worm of Dalhousie
University. "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?"
"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."
Dr. Worm notes that the recently-updated Red List issued by the
International Union for the Conservation of Nature assessed 59,508
species, of which 19,625 are classified as threatened. This means
the IUCN Red List, the most sophisticated ongoing study of its
kind, monitors less than 1% of world species.
The research is published alongside a commentary by Lord Robert May
of Oxford, past-president of the UK's Royal Society, who praises
the researchers' "imaginative new approach."
"It is a remarkable testament to humanity's narcissism that we know
the number of books in the US 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 May writes.
"(W)e increasingly recognize that such knowledge is important for
full understanding of the ecological and evolutionary processes
which created, and which are struggling to maintain, the diverse
biological riches we are heir to. Such biodiversity is much more
than beauty and wonder, important though that is. It also underpins
ecosystem services that -- although not counted in conventional GDP
-- humanity is dependent upon."
Drawing conclusions from 253 years of taxonomy since
Linnaeus
Swedish scientist Carl Linnaeus created and published in 1758 the
system still used to formally name and describe species. In the 253
years since, about 1.25 million species -- roughly 1 million on
land and 250,000 in the oceans -- have been described and entered
into central databases (roughly 700,000 more are thought to have
been described but have yet to reach the central databases).
To now, 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.
Drs. Mora and 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).
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.
Says Dr. Adl: "We discovered that, using numbers from the higher
taxonomic groups, we can predict the number of species. The
approach accurately predicted the number of species in several
well-studied groups such as mammals, fishes and birds, providing
confidence in the method."
When applied to all five known eukaryote* kingdoms of life on
Earth, the approach predicted:
Total: 8.74 million eukaryote species on Earth.
(* Notes: Organisms in the eukaryote domain have cells containing
complex structures enclosed within membranes. The study looked only
at forms of life accorded, or potentially accorded, the status of
"species" by scientists. Not included: certain micro-organisms and
virus "types", for example, which could be highly numerous.)
Within the 8.74 million total is an estimated 2.2 million (plus or
minus 180,000) marine species of all kinds, about 250,000 (11%) of
which have been described and catalogued. When it formally
concluded in October 2010, the Census of Marine Life offered a
conservative estimate of 1 million+ species in the seas.
"Like astronomers, marine scientists are using sophisticated new
tools and techniques to peer into places never seen before," says
Australian Ian Poiner, Chair of the Census' Scientific Steering
Committee. "During the 10-year Census, hundreds of marine explorers
had the unique human experience and privilege of encountering and
naming animals new to science. We may clearly enjoy the Age of
Discovery for many years to come."
"The immense effort entering all known species in taxonomic
databases such as the Catalogue of Life and the World Register of
Marine Species makes our analysis possible," says co-author Derek
Tittensor, who also works with Microsoft Research and the UN
Environment Programme's World Conservation Monitoring Centre. "As
these databases grow and improve, our method can be refined and
updated to provide an even more precise estimate."
"We have only begun to uncover the tremendous variety of life
around us," says co-author Alastair Simpson. "The richest
environments for prospecting new species are thought to be coral
reefs, seafloor mud and moist tropical soils. But smaller life
forms are not well known anywhere. Some unknown species are living
in our own backyards -- literally."
"Awaiting our discovery are a half million fungi and moulds whose
relatives gave humanity bread and cheese," says Jesse Ausubel,
Vice-President of the Alfred P. Sloan Foundation and co-founder of
the Census of Marine Life. "For species discovery, the 21st century
may be a fungal century!"
Mr. Ausubel 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.
In his analysis, Lord May says the practical benefits of taxonomic
discovery are many, citing the development in the 1970s of a new
strain of rice based on a cross between conventional species and
one discovered in the wild. The result: 30% more grain yield,
followed by efforts ever since to protect all wild varieties of
rice, "which obviously can only be done if we have the appropriate
taxonomic knowledge."
"Given the looming problems of feeding a still-growing world
population, the potential benefits of ramping up such exploration
are clear."
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 $US 364 billion. Fortunately, new
techniques such as DNA barcoding are radically reducing the cost
and time involved in new species identification.
Concludes 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?"
###
Census of Marine Life
Thanks to Census of Marine Life for this article.