Changing Climate Suitability for Dominant Eucalyptus Species May Affect Future Fuel Loads and Flammability in Tasmania

Abstract

Fire management is becoming increasingly relevant in our changing climate as fire frequency and intensity increases both on a global scale and locally in Tasmania. The distribution of fuel across the landscape has significant impacts on fire regimes, influencing connectivity and flammability of fuel load. Remote sensing techniques are often used to assess current fuel loads, but projections of future fuel distributions are necessary for longer term planning of fire management. Eucalyptus species are an important, dominant component of many Tasmanian forests, influencing fuel load and flammability. We modelled the current and future climate suitability for two Eucalyptus species (E. delegatensis and E. obliqua), using a suite of species distribution models (SDMs) and global climate models (GCMs) for mid (2041–2060) and end of century (2061–2080) time periods. The implications these changes may have for the distribution of these important fuel species in the future are discussed. All GCMs projected notable changes in potential distribution, with both species contracting substantially in some areas and E. obliqua also exhibiting considerable expansions in the west of Tasmania. On average, suitability for E. delegatensis expanded by 5% ± 1.8% (1658 km2), contracted by 67% ± 22.7% (24,591 km2) and remained unchanged in 26% ± 7.8% (8783 km2) by the end of the century. For E. obliqua suitability expanded by a much greater 17% ± 6.3% (24,398 km2), contracted by slightly less at 55% ± 16.8% (81,098 km2) and remained unchanged in 45% ± 16.8% (63,474 km2) by the end of the century. These changes in climate suitability have the potential to cause changes in the composition and structure of Tasmania’s forests, impacting fuel loads. However, the two species exhibited different responses, reflecting their current distributions and suggesting that generalisations regarding species’ responses to changing climates are not appropriate, even where the species are closely related. These results suggest that future fuel loads and flammability at the landscape scale may change, requiring longitudinal, flexible and adaptive future fire management. Assessing the specific effects of distributional changes and the mechanisms driving different responses to climate change are highlighted as further research opportunities.