Health

Extreme weather may drive flying foxes to seek ‘climate refuge’ as far south as Tasmania

Fruit bats may migrate as far south as Tasmania in the future as a result of extreme weather events linked to the climate crisis, new modelling suggests.

University of Tasmania scientists predicted the grey-headed flying fox could take “climate refuge” in the southernmost state in coming decades if greenhouse gas emissions continued on their current trajectory.

Tasmania is currently home to eight species of small bats, but no “megabats” such as flying foxes, also known as fruit bats, which are mostly found in eastern and northern Australia.

The study’s lead author, Vishesh Diengdoh, warned the encroachment of flying foxes into previously uninhabited areas could have significant effects on Tasmania’s ecosystems and agriculture.

“There may be some sort of human–wildlife conflict, especially with farmers in agricultural areas,” Diengdoh said.

With a wingspan of over one metre, the grey-headed flying fox is one of the largest bats in Australia. It is listed as a vulnerable species.

The research, which is published in preprint form and has not yet been peer reviewed, analysed the potential impact of extreme weather events such as heatwaves and drought on geographical distribution of fruit bat species in Australia.

The modelling took into account factors including rainfall, temperatures, the frequency and severity of heatwaves and vegetation.

The researchers first matched the model to the known geographical distributions of the bats, before using it to predict future ranges in 2050 and 2070.

Grey-headed flying foxes are temperature sensitive and previous heatwaves have resulted in mass death events in Victoria.

Under an intermediate scenario of carbon emissions, Tasmania would have a suitable climate for the bats to survive, with the study even suggesting human-assisted migration may be an option to “safeguard their population viability”.

“Both instances raise challenging socio-political questions that would benefit from discussion and debate now, rather than at some future crisis point.”

The range of the grey-headed flying fox has already expanded in the past 40 years, likely as a result of the changing climate. Dr Wayne Boardman, a wildlife veterinarian at the University of Adelaide who was not involved in the research, said the bats had arrived in Adelaide in the last decade.

Boardman said the 240km separating Tasmania and the Australian mainland was a plausible distance for the grey-headed flying fox to travel.

“They can travel upwards of 300 to 400km a night in the right conditions,” he said.

The arrival of flying foxes in Tasmania could lead to problems if flying foxes colonise commercial crops, said Boardman. In the past, costly relocation projects have ensued when the bats settled in urban areas.

Ku-ring-gai council on Sydney’s upper north shore announced this week it was considering an environmental buffer zone between local residents and a colony of 50,000 grey-headed flying foxes.

“Going on the present projection, it’s likely that the grey-headed flying foxes could seek to find resources in Tasmania in the next 10 to 20 years,” said Boardman. Any migration to Tasmania would require there to be sufficient food resources for the bats to thrive, he said.

Diengdoh said efforts to conserve flying fox habitats on the mainland may help to mitigate against any potential migration.

The study also modelled the distributions of six other fruit bat species, forecasting that extreme weather events would impact all of their future ranges.

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