Risk of extinction increases for endangered species

ENDANGERED species may be 100 times more at risk of extinction than most experts believe, it was claimed yesterday.

Methods used to determine which species should be on the “Red List” of those facing extinction greatly underestimate the danger, according to one US evolutionary biologist.

Dr Brett Melbourne, from the University of Colorado at Boulder, says they overlook a key factor — random differences between individuals in a given population.

Such differences may include variations in male-to-female sex ratio, as well as physical size or aspects of behaviour. Their influence on survival rates and reproductive success has an unexpectedly major impact on extinction risk, a study led by Dr Melbourne found.

“When we apply our new mathematical model to species extinction rates, it shows that things are worse than we thought,” he said. “By accounting for random differences between individuals, extinction rates for endangered species can be orders of magnitude higher than conservation biologists have believed.”

Currently, extinction risk models are mainly based on just two factors, said Dr Melbourne, whose research appears in the journal, Nature. One is the number of random events adversely affecting individuals within a population – for instance, the accidental drowning of a rock wallaby. The second is the impact of external, random events such as temperature and rainfall fluctuations that can influence birth and death rates.

To test the new mathematical models, Dr Melbourne’s team studied populations of beetles in laboratory cages.

More than 16,000 species worldwide are currently threatened with extinction, according to a 2007 report from the International Union for Conservation of Nature.