Koalas and climate change: a case study on the Liverpool Plains, north-west New South Wales

Koalas are prime candidates to study the impact of climate change because they are specialised folivores and lack any ready means of avoiding weather extremes. Koalas are widely but patchily distributed throughout eastern mainland Australia. Efforts to protect them from landscape-scale threats have been identified in the NSW 2008 Koala Recovery Plan, the 2010 NSW Priorities for biodiversity adaptation to climate change and the 2009-14 National Koala Conservation and Management Strategy. The statements in the formal strategies and recovery plans identify a number of problems, two of which we address in this paper. The first problem is that of extreme weather and the second is the change of leaf quality from rising levels of carbon dioxide. This paper capitalises on our field study in Gunnedah, in north-west NSW, which examined a 1990s success story where the local koala population benefited from the plantings of trees and shrubs to hold down the water table in the face of a rising salinity crisis. In late 2009, heatwaves killed an estimated 25% of the Gunnedah koala population. This foreshadows how increased climate variability will impact on koala populations. In 2008, chlamydiosis - a disease causing infertility - had been established as being present in the Gunnedah population. The likely spread of this disease throughout the Gunnedah koala population presents a further challenge to wildlife managers in the context of a changing climate. The potential indirect effects of global climate change - how increasing concentrations of atmospheric CO2 may reduce the availability of the nutrients in Eucalyptus foliage to koalas - is described and the implication drawn that elevated concentrations of atmospheric CO2 may threaten some populations of free-ranging koalas. The Liverpool Plains are among Australia's prime agricultural landscapes where the conservation of biodiversity occurs largely on private land. Consequently, we need to integrate climate change adaptation with rural land management and restoration practices. The research demonstrates the contribution from the cross-disciplinary links. It adds to our ability to monitor sustainable native fauna populations and threatened species by distinguishing among the multiple causes of population change, and it can also be viewed as a pilot demonstrating the value of longitudinal wild population disease monitoring.