The remaining koalas (Phascolarctos cinereus) of the Pilliga forests, north-west New South Wales: refugial persistence or a population on the road to extinction?
Daniel Lunney A B K , Martin Predavec A , Indrie Sonawane A , Rodney Kavanagh C D , George Barrott-Brown E , Stephen Phillips F , John Callaghan F , Dave Mitchell G , Harry Parnaby A , David C. Paull H , Ian Shannon A , Murray Ellis A , Owen Price I and David Milledge J
+ Author Affiliations
- Author Affiliations
A Office of Environment and Heritage NSW, PO Box 1967, Hurstville, NSW 2220, Australia.
B School of Life and Environmental Sciences, University of Sydney, NSW 2006, Australia and School of Veterinary and Life Science, Murdoch University, Perth 6150, Australia.
C Niche Environment and Heritage, PO Box 2443, North Parramatta, NSW 1750, Australia.
D Present address: Australian Wildlife Conservancy, GPO Box 4301, Sydney, NSW 2001, Australia.
E Office of Environment and Heritage, PO Box 2111, Dubbo, NSW 2830, Australia.
F Biolink Ecological Consultants, PO Box 3196, Uki, NSW 2484, Australia.
G Australian Koala Foundation, GPO Box 265, Brisbane, Qld 4001, Australia.
H Ethical Ecology, PO Box 67, Coonabarabran, NSW 2357, Australia.
I School of Biological Sciences, University of Wollongong, Wollongong, NSW 2522, Australia.
J Landmark Ecological Services, PO Box 100, Suffolk Park, NSW 2481, Australia.
K Corresponding author. Email: dan.lunney@environment.nsw.gov.au
Pacific Conservation Biology 23(3) 277-294 https://doi.org/10.1071/PC17008
Submitted: 15 March 2017 Accepted: 11 June 2017 Published: 18 July 2017
Abstract
In the 1990s, the Pilliga forests were carrying the largest population of koalas west of the Great Dividing Range in New South Wales (NSW). Whereas the NSW koala population in its entirety was thought to be in decline, the Pilliga population stood out as potentially increasing. By 2007, anecdotal evidence suggested that the population was in decline. We undertook surveys of koalas in the Pilliga forests that repeated surveys undertaken between 1991 and 2011. We found that koalas had declined and were found in only 21% of sites in which they were observed in the initial surveys – by any measure, a 5-fold drop in occupancy in less than two decades is severe. Declines occurred evenly across the Pilliga, with persistence at a site seemingly related to a high initial density of koalas rather than to a slower rate of decline. Sites where koalas persisted were characterised as having higher temperatures and lower rainfall relative to other sites, being close to drainage lines with deeper soils and having a lower occurrence of fire. This pattern fits with the observation in the recent surveys that koalas were next to drainage lines in the western half of the Pilliga and fits with the suggestion that koalas show refugial persistence. Recovery from this point is not assured and will depend on how we manage the landscape, particularly with the threat of climate change. This will likely require active management within an adaptive management framework, such as restoration of refuges, and not simply habitat reservation.
Additional keywords: climate change, extreme weather events, population decline, refuge, refugia
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