Global warming could save endangered sharks
Updated
New research in Australia has found that while global warming is bad news for many species, it could benefit one critically-endangered animal - the grey nurse shark.
Presenter: Jayne Margetts
Speakers: Associate Professor Corey Bradshaw, University of Adelaide; Professor Robert Harcourt, Macquarie University
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MARGETTS: Conservationists fear Australia's grey nurse shark could become extinct by 2050. But according to a group of leading shark scientists global warming could help save them. Associate Professor Corey Bradshaw is from the University of Adelaide.
BRADSHAW: This is probably one of those one in a hundred examples where climate change may actually be somewhat beneficial for this particular species.
MARGETTS: Australia has two grey nurse shark populations. One off the east coast - ranked as critically endangered. And one off the west coast - categorised as vulnerable. Scientists believe the two groups have been isolated from one another for more than 100,000 years. Professor Bradshaw says they are sensitive to temperature so the cold water of the Victorian and South Australian coasts has prevented them from migrating south.
BRADSHAW: They really don't often go through Bass Strait. If they do it's never been recorded. We've already seen massive warming in the south east and we're likely to see a lot more in the next 50 to 70 years which will mean that the minimum temperature is reached for the southern Australian coastline, so these animals will be able to go quite happily along the southern coast and therefore join up the two populations
MARGETTS: He says that could prevent the grey nurse shark from becoming extinct.
BRADSHAW: The fundamental component of this is that if you've got a population that suddenly becomes larger, so that essentially the grey nurse shark in Australia become one giant population from Broome right through to mid Queensland, the possibility that any one catastrophic event or fishing would knock the population on its head and make it go extcint is reduced.
MARGETTS: But Professor Corey Bradshaw says grey nurse sharks are still vulnerable to other threats such as commercial and recreational fishing.
BRADSHAW: Climate change may assist a little bit in preventing total extinction but it doesn't negate all the other sources of mortality. So climate change isn't going to solve all the problems all it does is gives us a little bit more of a window to do something positive.
MARGETTS: Professor Robert Harcourt from Sydney's Macquarie University says a change in fishing methods - such as using a different type of hook - is the best way to keep the population going.
HARCOURT: It's very clear that one of the most important impacts on the grey nurse shark fishing hook mortality. A large proportion of the population has fishing hooks in them and of the animals that are brought in dead, some of them have bled to death, because they've had an artery or a vein punctured by a hook.
MARGETTS: Conservationists also want to increase the size and number of areas where grey nurse sharks are protected.
