Tropical species moving in

Written By miftah nugraha on Sabtu, 16 Februari 2013 | 19.55

DIVERS and fishermen along Tasmania's East Coast have started to find green rock lobsters.

Until recently Tasmania's rock lobster population has always been the red-coloured southern rock lobster species.

It appears that rapidly warming waters off Tasmania's East Coast have enabled members of the green-coloured eastern rock lobster species to muscle in.

University of Tasmania Institute of Marine and Antarctic Studies (IMAS) senior research fellow Greta Pecl said the green lobsters had been visiting Tasmanian waters for some years.

But Redmap, an IMAS initiative that invites the public to report and send in photos of unusual marine life sightings, last year turned up the first evidence that the eastern lobsters had made Tasmania's East Coast seabeds their home.

A green lobster community with at least 35 individuals of various ages was found occupying an East Coast den.

They, along with the pest centrostephanus rodgersii sea urchin species, are among the first in a new wave of emigrants to Tasmania, consistent with climate change predictions.

Dr Pecl and colleague Neil Holbrook said more scientific study would be needed before it was proven that climate change had a hand in such colonisation.

They say it is beyond doubt that the East Australian Current has extended south by about 350km during the past 50 years to reach Tasmanian waters.

The powerful current pushes seawater south from the tropics at speeds of 5km/h. Its southerly extension has created one of the world's fastest-warming ocean hot spots along Tasmania's East Coast.

The current was made famous in the animated film Finding Nemo. It helped the characters Marlin and Dory to complete their long swim south, from the tropics to Sydney Harbour, where they were reunited with the wayward Nemo.

In real life, the current has enabled fish such as marlin, yellow-tailed kingfish, snapper, yellowfin tuna and dolphin fish to swim all the way to Tasmania.

But most of those fish have been strays, or visitors. Their species haven't yet made a permanent move to Tasmania.

Copula Sivickisi, a close relative of the box jellyfish, appears to be the state's most recently discovered visitor. A single jellyfish was last month dropped off alive at the CSIRO in Hobart.

Dr Pecl said there was also growing evidence that the gloomy octopus were setting up homes in Tasmanian waters.

The East Australian Current is providing East Coast divers, fishers, as well as armchair enthusiasts who visit the Redmap website, with a "preview trailer" on what climate change could bring to Tasmania.

Also beyond doubt, says Nathan Bindoff, an IMAS research program leader and a Climate Futures for Tasmania project author, is the fact that climate change exists.

Professor Bindoff said that since the 1960s temperatures had been rising at about 0.1 of a degree a decade, and rising greenhouse gas levels could account for all of that.

He said the warming rate was forecast to accelerate, to make Tasmania as much as three degrees warmer by the end of the century.

Will there be invasion forces of land-based insect, bird and mammal species lined up along the Victorian coastline to stage D-day-style assaults on Tasmania as the state warms?

At this stage scientists have identified just a few potentially hostile invaders. An obvious candidate is fruit fly, which could stow away in incoming fresh food or vegetable matter.

Fruit fly has the potential to wipe millions of dollars off the value of Tasmanian fruit industries simply by landing here.

"There are still some years before fruit fly can settle permanently in Tasmania," Prof Bindoff said. "They could land here, but would be unable to get through the cold winters."

Models used by the Framework for Action on Climate Change have mapped out an area of Tasmania's far North-East that could support fruit fly during some winters starting about 2036.

The model shows that semi-permanent zone spreading south and west along the coast during the century's second half, and by 2071 the far North-East and Flinders Island could become permanently fruit fly-friendly.

Prof Bindoff said termites were another potential -- and unwanted -- emigrant later this century.

University of Tasmania School of Zoology professor Chris Johnson said many of the exotic species with the greatest potential to make their mark on Tasmanian landscapes as climate change progressed could have already arrived.

Prof Johnson said the change that Tasmanians would probably notice most, as the state's climate warmed, would be an increased frequency of extremely hot days, and associated catastrophic fire risks.

He said there were no guarantees that habitats such as wet eucalypt forests could revert back to their original states as fire pressure increased.

Prof Johnson said there could be opportunities for exotic animals such as deer to trample or eat down regrowth, which could radically change the look and feel of the forest that grows back.

He said increased disturbance could also favour animals such as feral cats and rodents at the expense of native marsupials.

Prof Johnson said exactly how landscapes, and the animals within, would respond to increased fire as well as rain and flooding pressure was impossible to predict without studies and models, but there was a high probability that a lot of Tasmania's natural vegetation types could be permanently changed.

"It is hard to see how something like that is not going to happen," he said.

Aedes camptorhynchus is another little-known critter already in Tasmania with the potential to attract a lot more attention in the long term.

It is a mosquito species that carries the Ross River virus.

Climate change models foreshadow more extreme rain events, associated with increased evaporation from oceans.

In coastal Tasmania such soakings could be favourable to the mosquitoes. It could create ideal conditions for virus spread, if the mosquitoes are a short flying distance away from areas populated by people and native animals which act as virus reservoirs.


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