Climate change and other factors influencing the decline of the Tasmanian cider gum (Eucalyptus gunii)

Global climatic change has been strongly implicated in the decline of many species. However, other processes can contribute towards the extinction risk of these species. Could management of these processes arrest or slow climatically related decline? We test the relationship between climate change, and other potential threatening factors, and the decline of Eucalyptus gunnii, a tree endemic to the subalpine regions of Tasmania, Australia. Through observing the spatial patterns of both climatic change and dieback, we found there was a stronger pattern of increasing droughts in the eastern part of the species range, the region which also displayed the worst dieback. A time series of aerial photographs revealed that the most severe drought periods in the last several decades have coincided with the most rapid tree decline. However, the sites that suffered the worst dieback were also more heavily used for stock grazing, a factor which had a stronger spatial relationship with tree decline than climate. Other factors were also implicated in the decline, including possum browsing. The good health of some populations in the most climatically stressed areas suggests that the amelioration of non-climatic stresses could be effective in maintaining the health of the surviving populations.