Projected changes in Australian fire regimes during the 21st century and consequences for ecosystems

摘要

Climate projections show Australia becoming significantly warmer during the 21st century, while precipitation decreases over much of the continent. Such changes are generally considered to increase wildfire risk. Nevertheless, using a process-based model of vegetation dynamics and vegetation–fire interactions, we show that while burnt area increases in southern and central Australia, it decreases in northern Australia. Overall the projected increase in fire by the end of the 21st century is small (0.7–1.3% of land area equivalent to 12–24% of current burnt area, depending on the climate scenario). The direct effects of increasing CO2 on vegetation productivity and water-use efficiency influence simulated fire regimes: CO2 effects tend to increase burnt area in arid regions, but increase vegetation density and reduce burnt area in forested regions. Increases in fire promotes a shift to more fire-adapted trees in wooded areas and their encroachment into grasslands, with an overall increase in forested area of 3.9–11.9% of land area by the end of the century. The decrease in fire in northern Australia leads to an increase in tree cover (ca 20%) and an expansion of tropical forest. Thus, although the overall change in burnt area is small it has noticeable consequences for vegetation patterns across the continent.