干旱区生态环境知识资源中心

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, 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 burnt area promote 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 burnt area in northern Australia leads to an increase in tree cover (similar to 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.