Direct climate change impacts on growth and drought risk in blue gum (Eucalyptus globulus) plantations in Australia

Abstract

ABSTRACTAustralia’s climate is changing and Australia’s forests have been identified as vulnerable to climate change impacts. The process-based model CABALA, an ensemble of global circulation models, and a range of scenarios on plant response to elevated CO2 (eCO2) and site conditions, were used to predict the direct effects of climate change on the productivity and mortality risks for Australia’s blue gum (Eucalyptus globulus) plantation estate. The modelling showed considerable uncertainty about future outcomes across large parts of the estate, with best-case and worst-case scenarios varying from decreased to increased production. In some areas we can be confident of future outcomes. Nevertheless, it is clear that, across the whole estate, appropriate management can reduce risk and ensure that we are able to capitalise on potential beneficial aspects of climate change. Under most future scenarios, without adaptation, the drier parts of the plantation estate are at risk. However, in all but the eastern areas of Western Australia, and at the driest margins of the estate in South Australia and Victoria, adaptation options can reduce risk and ensure productivity. Other areas currently at the cold margins of the estate, notably the highlands of Victoria and across Tasmania, appear to increase in productivity under most future scenarios. Even in those areas where productivity may potentially increase, experience suggests that pests and diseases may pose a risk. If we are to benefit from any aspect of climate change, then pursuit of best-practice sustainable forest management is critical. The greatest source of uncertainty in forecasts is associated with how photosynthesis in field-grown trees will respond to elevated atmospheric carbon dioxide levels (eCO2). Regional differences in global circulation model forecasts are important, particularly in Western Australia, where the extent of future rainfall decline significantly impacts predictions. Local site factors, exemplified in this study by soil depth, will play an important role in modulating climate change impacts, particularly through their role in constraining responses to eCO2.