The world has 8.7 million species
The estimate is based on how species are
classed together, using a system developed by Linnaeus in the 18th
century
by Michael McCarthy
Noah’s Ark could never have contained them: there are probably about
8.7 million species of living things, the vast majority of them
undiscovered, according to what is believed to be the most authoritative
estimate ever carried out of the scale of life on earth.
So far, about 1.2 million species, ranging from microscopic insects
to the blue whale, the largest living creature, have been described, but
it has always been recognised that the true total is very much higher.
Previous estimates have ranged from three million, right up to 100
million, but the new figure, based on an innovative analytical
technique, dramatically narrows the range of possibilities.
The assessment, by scientists from the Census of Marine Life, a
10-year international study of life in the oceans which reported last
year, indicates there are 6.5 million species living on the land and 2.2
million about a quarter of the total in the oceans.
Yet 86 per cent of the terrestrial species and 91 per cent of the
marine species have yet to be discovered, described and catalogued, with
many of them likely to be small creatures in inaccessible locations,
such as beetles in the rainforest canopy or marine animals in the deep
ocean (although large animals are still being found in countries such as
Vietnam and Papua New Guinea).
“The question of how many species exist has intrigued scientists for
centuries and the answer... is particularly important now because a host
of human activities and influences are accelerating the rate of
extinctions,” said Camilo Mora of the University of Hawaii and Dalhousie
University in Halifax, Canada, one of the lead authors of the study.
“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,” he added.
The estimate is based on the way species are classed together, using
the taxonomic classification system developed by the Swedish biologist
Linnaeus in the 18th century, which is still in use today.
This groups forms of life in a pyramid-like hierarchy, ranked upwards
from species to genus, family, order, class, phylum, kingdom and domain.
Analysing data on ocean species, the scientists spotted a numerical
pattern linking the higher taxonomic levels to species numbers, which
allows the latter to be predicted.
- The Independent
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