Wildlife extinction rates 'seriously underestimated'
Scientists have discovered that endangered species may become extinct 100 times faster than previously thought - which is a bleak re-assessment of the threat to global biodiversity.
Writing in the journal Nature, leading ecologists claim that methods used to predict when species will die out are seriously flawed, and dramatically underestimate the speed at which some plants and animals will be wiped out.
The findings suggest that animals such as the western gorilla, the Sumatran tiger and the Malayan sun bear, the smallest of the bear family, may become extinct much sooner than conservationists feared.
Ecologists Brett Melbourne at the University of Colorado at Boulder and Alan Hastings at the University of California, Davis, said conservation organisations should use updated extinction models to urgently re-evaluate the risks to wildlife.
"Some species could have months instead of years left, while other species that haven't even been identified as under threat yet should be listed as endangered," said Melbourne.
The warning has particular implications for the International Union for the Conservation of Nature, which compiles an annual "red list" of endangered species. Last year, the list upgraded western gorillas to critically endangered, after populations of a subspecies were found to be decimated by Ebola virus and commercial trade in bush meat. The Yangtze river dolphin was listed as critically endangered, but is possibly already extinct.
The researchers analysed mathematical models used to predict extinction risks and found that while they included some factors that are crucial to predicting a species' survival, they overlooked others. For example, models took into account that some animals might die from rare accidents, such as falling out of a tree. They also included chance environmental threats, such as sudden heatwaves or rain storms that could kill animals off.
But the two researchers also looked at some different factors that would affect the rate of extinction.
But Melbourne and Hastings highlighted two other factors that extinction models fail to include, the first being the proportion of males to females in a population, the second the difference in reproductive success between individuals in the group. When they factored these into risk assessments for species, they found the danger of them becoming extinct rose substantially.
"The older models could be severely overestimating the time to extinction. Some species could go extinct 100 times sooner than we expect," Melbourne said.
The researchers showed that the missing factors - the number of males to females, and variations in the number of offspring - were capable of causing unexpected, large swings in the size of a population, sometimes causing it to grow, but also increasing the risk that a population could crash and become extinct.
More that 16,000 species all over the world are currently being threatened with extinction.
One in four mammal species, one in eight bird species and one in three amphibian species are on the organisation's red list. An updated list is due to be published in October.
This site shows all the animals that are either endangered or extinct and the list is long and depressing.
An Independent article last year, talks about how a species becomes endangered.
In the final stages of dehydration the body shrinks, robbing youth from the young as the skin puckers, eyes recede into orbits, and the tongue swells and cracks. Brain cells shrivel and muscles seize. The kidneys shut down. Blood volume drops, triggering hypovolemic shock, with its attendant respiratory and cardiac failures. These combined assaults disrupt the chemical and electrical pathways of the body until all systems cascade toward death.
Such is also the path of a dying species. Beyond a critical point, the collective body of a unique kind of mammal or bird or amphibian or tree cannot be salvaged, no matter the first aid rendered. Too few individuals spread too far apart, or too genetically weakened, are susceptible to even small natural disasters: a passing thunderstorm; an unexpected freeze; drought. At fewer than 50 members, populations experience increasingly random fluctuations until a kind of fatal arrhythmia takes hold. Eventually, an entire genetic legacy, born in the beginnings of life on earth, is removed from the future.
Scientists recognise that species continually disappear at a background extinction rate estimated at about one species per million per year, with new species replacing the lost in a sustainable fashion. Occasional mass extinctions convulse this orderly norm, followed by excruciatingly slow recoveries as new species emerge from the remaining gene-pool, until the world is once again repopulated by a different catalogue of flora and fauna.