When there'S a large and sudden fall in the population of a species, as occurred for many plants and animals due to last summer's bushfires, its extinction risk increases dramatically. "When a population becomes really sparse a particular set of ecological processes called an extinction vortex can occur and a species is far more likely to be sucked into this when its numbers are low," explains Dr Brendan Wintle, professor in conservation ecology at the University of Melbourne. "When a species' numbers are massively reduced, the extinction risk is increased simply because it's less able to deal with all the other challenges it faces. So if you kill half the number of individuals of a species, which could well have happened for many species during theBlack Summer fires, like the long-footed potoroo, you expose them to the extinction vortex. It can also be a dire problem for wide-ranging animals like quolls, which are so sparsely spread they can't find mates."In Victoria's 2009 fires Leadbeater's possums suffered huge losses, putting the species at risk of being sucked into a vortex.
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