Bushfires 'down under': patterns and implications of contemporary Australian landscape burning

Abstract

Australia is among the most fire-prone of continents. While national fire management policy is focused on irregular and comparatively smaller fires in densely settled southern Australia, this comprehensive assessment of continental-scale fire patterning (1997–2005) derived from ~1 km2 Advanced Very High Resolution Radiometer (AVHRR) imagery shows that fire activity occurs predominantly in the savanna landscapes of monsoonal northern Australia. Statistical models that relate the distribution of large fires to a variety of biophysical variables show that, at the continental scale, rainfall seasonality substantially explains fire patterning. Modelling results, together with data concerning seasonal lightning incidence, implicate the importance of anthropogenic ignition sources, especially in the northern wet–dry tropics and arid Australia, for a substantial component of recurrent fire extent. Contemporary patterns differ markedly from those under Aboriginal occupancy, are causing significant impacts on biodiversity, and, under current patterns of human population distribution, land use, national policy and climate change scenarios, are likely to prevail, if not intensify, for decades to come. Implications of greenhouse gas emissions from savanna burning, especially seasonal emissions of CO2, are poorly understood and contribute to important underestimation of the significance of savanna emissions both in Australian and probably in international greenhouse gas inventories. A significant challenge for Australia is to address annual fire extent in fire-prone Australian savannas.

Ecological Implications of Fine-Scale Fire Patchiness and Severity in Tropical Savannas of Northern Australia

“…The chance that it burned in each year was the product of the probability of a fire occurring (set at 0.3 for all simulations to reflect typical savanna fire return intervals under higher rainfall conditions; e.g. Russell-Smith et al 2007) and the percentage burned by the fire, which was set as one of four levels (50, 83, 93 or 100). The 83% and 93% values reflect levels of the burned area in EDS and LDS fires found in this study, and the bounding 50% and 100% values are used for comparisons.…”

“…Over that vast region, annual fire frequencies range from over 50% in higher rainfall regions to <5% in heavily grazed semi-arid savanna regions, with an overall mean frequency of 19%, over the period 1997(Russell-Smith et al 2007. In these ecosystems, fire is a natural ecological process required for maintaining biological diversity (Russell-Smith et al 2002a, Bowman et al 2003.…”

Emissions of trace gases from Australian temperate forest fires: emission factors and dependence on modified combustion efficiency

“…Most of the area burnt in Australia annually is in the semi-arid and tropical savannas in the north of the country (Russell- Smith et al, 2007), but large bushfires also occur regularly in the temperate forests that cover extensive areas of the south-east of Australia (Cai et al, 2009). These fires can be intense enough to create pyro-convective lofting and inject smoke at high altitudes (Fromm et al, 2006;Dirksen et al, 2009;Guan et al, 2010) and are expected to become more frequent under a 15 changing climate (Bradstock et al, 2009;Cai et al, 2009;Keywood et al, 2013;King et al, 2013).…”

Atmospheric mercury in the Southern Hemisphere tropics: seasonal and diurnal variations and influence of inter-hemispheric transport

“…Slemr et al, 1985). The atmospheric lifetime of GEM is currently estimated at 5-12 months (Holmes et al, 2006(Holmes et al, , 2010Selin et al, 2007;Horowitz et al, 2017).…”