Causes of the Widespread 2019–2020 Australian Bushfire Season

Abstract

The recent bushfires (2019-2020) in New South Wales (NSW) Australia were catastrophic by claiming human and animal lives, affecting ecosystems, destroying infrastructure, and more. Recent studies have investigated relationships between hydroclimatic signals and past bushfires, and very recently, a few commentary papers claimed drought and fuel moisture content as the probable causes for the widespread 2019-2020 bushfires. Therefore, in this study, a novel work of encompassing a wide range of factors attributing to the recent bushfires is presented. Empirical evidence-based statistical methods are used to identify the hydroclimatic variables and geomorphic characteristics contributing to the 2019-2020 bushfires. The results highlight that ongoing drought, surface soil moisture (SSM), wind speed (WS10), relative humidity (RH), heat waves (HW), dead and live fuel moisture, and certain land cover types create favorable conditions for fire ignition and aid in fire propagation in different regions of the NSW state. The findings suggest that accounting for the above-identified variables in bushfire prediction and monitoring system are crucial in avoiding such catastrophes in the future. The overarching application of this study is developing robust and more versatile fire protection planning and management. Plain Language Summary Since the 2019-2020 Australian bushfires were catastrophic in terms of burnt area and severity, a detailed analysis of the primary causes is crucial. In this paper, several probable causes are tested statistically to establish their relationship with the burnt area. The results indicate that the ongoing drought, surface soil moisture, wind speed, relative humidity, heat waves, dead and live fuel moisture, and land cover with certain vegetation (particularly native eucalyptus and grazing land) are the primary causes of the widespread bushfire. These results are extremely critical in updating the current bushfire planning and management.

Intensifying Australian Heatwave Trends and Their Sensitivity to Observational Data

“…Our results also indicate that excess heat during heatwaves (HWC) and extreme heatwave intensity (HWA) are increasing at a rapid rate over the southern and southeastern regions of Australia compared to the other parts of Australia (Figure 1). The hotter heatwaves over the southern and southeastern Australian regions have severe implications for human health (Williams et al, 2018), agricultural productivity (Herold et al, 2018), the livestock industry (Henry et al, 2012), and other extreme events like bushfires (Deb et al, 2020;Jyoteeshkumar reddy et al, 2021;Sharples et al, 2016).…”

“…Australian heatwaves have other societal impacts on the productivity of crops and livestock (Asseng et al, 2011), infrastructure, and power supply (McEvoy et al, 2012). Heatwaves also play a critical factor in increasing bushfire risk (Clarke et al, 2013;Deb et al, 2020;Jyoteeshkumar reddy et al, 2021). While heatwaves are typical of the Australian climate, they are rare (by definition) in a stochastic climate.…”

“…1). The hotter heatwaves over the southern and southeastern Australian regions have severe implications for human health (Williams et al, 2018), agricultural productivity (Herold et al, 2018), the livestock industry (Henry et al, 2012), and other extreme events like bushfires (Deb et al, 2020;Jyoteeshkumar reddy et al, 2021;Sharples et al, 2016).…”

The carbon cycle of southeast Australia during 2019-2020: Drought, fires and subsequent recovery

“…Southeast Australia has been in drought since 2017, with the 2017-2019 period having the largest three year rainfall deficit since 1900 (King et al, 2020). These conditions have been most extreme during 2019, which was the hottest and driest year recorded in southeast Australia (Abram et al, 2020;Bureau of Meteorology, 2020), preconditioning one of the worst bushfires seasons in recorded history (Nolan et al, 2020;King et al, 2020;Deb et al, 2020;Boer et al, 2020;Ward et al, 2020;Collins et al, 2021). These extreme conditions subsided in early February 2020 with heavy rainfall and cooler conditions, which persisted throughout the austral autumn.…”

Exploring PRISMA Scene for Fire Detection: Case Study of 2019 Bushfires in Ben Halls Gap National Park, NSW, Australia

“…Australia has experienced mega fires in the past, and a few in the current centurythe Canberra bushfires (2003) and Black Saturday (2009) [15,16]-however, the 2019-20 bushfire season was the most widespread, extreme and catastrophic that Australia has ever experienced since European settlement [16]. Prolonged drought in conjunction with high maximum temperatures and strong winds [17,18] and the hydroclimatic variables and geomorphic characteristics (the surface soil moisture, wind speed, relative humidity, heat waves, dead and live fuel moisture and certain land cover types) [16] created the optimal conditions for the bushfires of 2019-2020 to ignite and spread. December 2019 was the warmest in 110 years of record for NSW and the monthly accumulated Forest Fire Danger Index [19] was the highest on record over most of the Australia including NSW [20].…”