From the Torygraph
Extinction threatens more species than thought
By Roger Highfield, Science Editor
Last Updated: 6:01pm BST 02/07/2008
The true number of species at risk of extinction is likely to be many times higher than the current official estimate of 16,000, scientists have warned.
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A new study concludes that the risk that an endangered species will disappear completely may be underestimated by as much as 100-fold using present methods.
The International Union for Conservation of Nature estimates more than 16,000 species worldwide are threatened with extinction: one in four mammals, one in eight bird species and one in three amphibian species are on the IUCN "Red List."
Red flour beetles, Tribolium castaneum, were used in the research
Today, a warning that the figure may have to be revised sharply upwards comes from a study led by Dr Brett Melbourne of the University of Colorado, Boulder. A mathematical "misdiagnosis" has created the wrong impression that above a relatively small population size, extinction is unlikely.
The authors conclude "extinction risk for many populations of conservation concern needs to be urgently re-evaluated."
Dr Melbourne told the Telegraph that the finds do not mean that 100 times more species are now at risk but said the overall number, once the details are understood, "should be revised up by a large amount."
Although this work might not affect estimates of the risk of high profile endangered species like mountain gorillas, where biologists can collect data on specific individuals to help develop and track extinction, it will apply to many other species, like stocks of marine fish, where the best biologists can do is to measure abundances and population fluctuations.
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"I'm reluctant to mention particular species because each case will be different and one would have to analyse the data for that species," he said. The study will also lead to a revision of research published four years ago, also in the journal Nature, that warned a million species worldwide are threatened with extinction by climate change over the next half century.
The new study suggests that the shifts in the distribution of some species, such as amphibians, grasses, migratory birds and butterflies will have a much bigger effect on the variety of life.
Dr Melbourne said current mathematical models used to determine extinction threat, or "red-listed" status, of species worldwide overlook random differences between individuals in a given population.
Such differences, which include variations in sex ratios as well as size or behavioural variations between individuals that can influence their survival rates and reproductive success, have an unexpectedly large effect on calculations of extinction risk.
"When we apply our new mathematical model to species extinction rates, it shows that things are worse than we thought," said Dr Melbourne.
"By accounting for random differences between individuals, extinction rates for endangered species can be orders of magnitude higher than conservation biologists have believed."
"Almost all previous studies don't include all of the factors we studied, so it is fair to say that most previous studies suffer from this inadequacy. One general message from our work is that population sizes might need to be much larger for species to be relatively safe from extinction."
The study is published today in Nature with Prof Alan Hastings of the University of California, Davis and places greater emphasis on sex ratio variations and physical variation between individuals within a population.
"There has been a tendency to misdiagnose randomness between individuals in a population by lumping it with random factors in the environment, and this underestimates the extinction threat" said Dr Melbourne.
To confirm their thinking, the researchers monitored populations of red flour beetles - Tribolium castaneum - in laboratory cages, showing that the old models underplayed the importance of different types of randomness, so called stochastic effects, much like miscalculating the odds in an unfamiliar game of cards because you don't understand the rules, he said, adding "the effect we have uncovered here will be larger in natural populations."
The paper concludes: "Our results demonstrate that current estimates of extinction risk for natural populations could be greatly underestimated because variability has been mistakenly attributed to the environment rather than the demographic factors."
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