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A small koala DNA study conducted at Port Stephens appears to suggest that koala populations in the area are experiencing increasingly limited gene flow between isolated clusters.
Conservationist groups who ordered and participate in the study fear that the loss of genetic diversity in the animals could mean future generations are unable to fight off new disease, or to adapt to climate change.
The small-sample research was commissioned by the World Wide Fund for Nature as part of its 'Koala Forever' plan to double the eastern Australian population by 2050, and conducted by researchers from Federation University in Sydney who analysed scat samples from 39 koalas in the Port Stephens area belonging to two main population clusters there.
More on this issue: Port Stephens' new koala hospital kept busy with furry patients
Researchers indicated that further studies of larger sample sizes would be needed to shore up results, but initial findings suggested that gene flow was most limited in a peninsula population of Koalas near Tomaree and Tilligerry, and that limitations were beginning to appear in an inland population at Ferodale and Balickera on the Pacific Highway.
As the koala's natural habitat has receded, and become fragmented by suburban development, road building, and industry expansion, koalas have found it increasingly difficult to migrate and diversified breeding has become limited, ecologist attached to the study have said.
"Now koalas are confined to smaller patches of forest surrounded by inhospitable habitat such as houses, buildings, roads and farmland, it's difficult for koalas to disperse and migrate, as they are programmed to do, and often proves fatal," koala conservation ecologist Olivia Woosnam, who co-authored the study report, said.
The WWF and OWAD Environment - a koala ecology group which used specialist detection dogs to collect faeces samples for the study - have used the results to call for habitat preservation at Port Stephens, and for well-designed infrastructure to allow koalas to cross the Pacific Highway and promote gene flow, particularly between the Ferodale and Balickera populations, which they say would benefit populations on both sides of the road.
"Habitat fragmentation, which impedes gene flow, is a major problem for koalas and other species. That's why a major focus of Koalas Forever is to protect existing habitat, regenerate cleared forests, and to plant tree corridors to reconnect isolated populations," Darren Grover, of WWF-Australia, said.
Genetic data analysed as part of the inquiry showed the peninsula and inland clusters were once connected. However, the report noted that peninsula koalas "are now significantly different from those sampled further inland suggesting that gene flow between peninsula and inland koalas has been restricted over recent generations".
In October last year, Federal Environment Minister Sussan Ley approved the controversial extension of the Brandy Hill quarry, despite strong opposition from residents who feared the project would clear up to 52 hectares of koala habitat.
Ms Ley said strict new conditions had been attached to the project, including the establishment of a 74-hectare koala habitat corridor to support the local populations.
Members of the Save Port Stephens Koalas campaign, which attracted celebrity endorsements to opposing the quarry expansion, feared that after losing a quarter of the local koala population to devastating the summer bushfires of 2019, the surviving natural habitat would be crucial to the future of the survival of the local population.
Dive deeper: Port Stephens koalas and the Brandy Hill Quarry expansion:
- Brandy Hill Quarry expansion plans will destroy 50 hectares of koala habitat(January 15, 2020)
- Brandy Hill residents fear for koala population if quarry expands(June 30, 2020)
- Resident bid to save koalas from Brandy Hill Quarry expansion(August 21, 2020)
- Koala experts from University of Newcastle urge government to consider impact on habitat in expansion approval(September 3, 2020)
- Federal government under pressure to reject Brandy Hill quarry expansion(September 6, 2020)
- Brandy Hill Quarry expansion plan delayed, Brandy Hill and Seaham Action Group say proposal could disrupt koala habitat(September 7, 2020)
- Federal Environment Minister Sussan Ley visits Brandy Hill and scene of koala controversy(September 30, 2020)
- Save Port Stephens Koalas vows to keep pressure on as Federal Environment Minister delays Brandy Hill quarry decision(October 8, 2020)
- Save Port Stephens Koalas campaign rolls on with Brandy Hill Hanson quarry decision delay(October 8, 2020)
- Koala habitat to be cleared for controversial Brandy Hill quarry extension, approved by Environment Minister Sussan Ley (October 27, 2020)
- Premier Gladys Berejiklian's gifts Port Macquarie with a Koala hospital expansion as Port Stephens gets heartbreak(October 28, 2020)
- Wildlife conservation scientist: Brandy Hill quarry expansion into koala habitat 'not a message that we want to be sending' (October 28, 2020)
- Quarry decision means a koala breeding program is more important than ever: Port Stephens Koalas(October 31, 2020)