The incessant and devastating wildfires in Australia summer 2019/2020 have so far killed at least 34 people and is threatening to cause ecosystem collapse and drive species found only on the Australian continent to extinction (Lam et al., 2020).

Australia’s temperate broadleaf forests, dominated by eucalypts, are among the most fire-prone in the world and fires are common. The 2019/2020 fires are, however, unprecedented. According to a recent analysis, more than one fifth of the Australian temperate broadleaf and mixed forest biome has so far been burned in a single season. Typically, less than 2% burn annually, even in more extreme fire seasons (Boer et al., 2020).

In New South Wales, the region most heavily affected by the fires, more than 3,000 homes have been destroyed since the fires began early Spring. At that time, much of Australia was already in a state of drought, due to months of unprecedented hot and dry weather. Smoke from the fires is causing air pollution levels on a par with the most polluted cities in the world, implying that substantive health damage in terms of, e.g., cardiovascular and respiratory death and disease, must be expected (Yu et al., 2020).

Extreme heat and drought laid the ground

Australia experienced an extended period of heatwaves on December 2018 and January 2019, and overall the summer of 2018-2019 was the warmest on record. 2019 ended on the same note, with December being the warmest on record. In the middle of December 19, a slow-moving high pressure system brought a record-breaking heatwave, that affected almost all of Australia at some point. The 18th of December was the hottest day on record for the country, with an average temperature of 41.9⁰C. The year 2019 was also the driest year on record, mostly caused by a strong positive Indian Ocean Dipole (a natural but irregular oscillation of the sea surface temperatures in the western Indian Ocean that affects Australian weather).

The long period of draught ahead of the wildfire season laid the ground for the unconstrained spread of the 2019/2020 forest fires. Eucalyptus forest fires spread primarily through the litter layer, which was extremely dry in 2019. Moreover, swamps, gullies and other landscape features that work as naturally occurring firebreaks, had dried out (Boer et al., 2020).

Mean temperature anomalies over Australia (as calculated from the 1961-1990 average). The black line shows the 11-year moving average. @Bureau of Meteorology, Australia. http://www.bom.gov.au/climate/current/annual/aus/#tabs=Temperature

No fire without a spark

Whereas drought increases the risk of wildfires and how effectively they are spread, human beings are usually the ones responsible for igniting the fires. Lightning is a natural phenomenon that can ignite fires, but the main cause of wildfires is anthropogenic, resulting from agriculture and forest management practices, as well as from recreational habits (Sofiev, 2013). Globally, changed agricultural practices seem to have contributed to a decline in the areas subject to wildfires during the past decades (Andela et al., 2017). On the other hand, the economically and socially most destructive fires are associated with human settlements, particularly those located in suburban areas intermixed with flammable forest. Due to the complexity in what causes wildfires, modelling future wildfire risk is complicated. Climate models indicate that the number of days conducive to extreme wildfire events may increase with 20-50% in disaster-prone landscapes such as those found in Australia, western USA and European Mediterranean Basin (Bowman et al., 2017).  Recent results from the ‘FireMIP intercomparison project’, however, shows the importance of appropriate representation of land use and human behavior in projections of wildfires (Sanderson and Fisher, 2020).

Immediate and looming health risks

The horror of people being stuck in the wildfire flames is perhaps the most tangible effect on humans of the fires. However, in addition to the immediate danger to lives and livelihood, exposure to air pollution caused by the fires poses a substantial risk to human health. It is well established that exposure to fine particulate matter (PM2.5), a major component in wildfire smoke, increases the risk of death and disease. Risks are higher for certain vulnerable groups, such as older adults, infants, and people with chronic diseases. Moreover, some studies indicate that the increase in mortality during wildfires appear to be larger than what would be expected from the increased pollution levels only, indicating a higher toxicity (Analitis et al., 2012). 

In addition to the immediate danger to lives and livelihood, exposure to air pollution caused by the fires poses a substantial risk to human health. Photo taken in Canberra 5 january. Daniiielc, iStock.

Monitoring data show that the daily mean PM2.5 concentration has been reaching well above 500 micrograms/m3 in some areas, e.g. in Sydney and Canberra in early January (NSW Department of Planning, Industry and Environment, 2020). This is more than 20 times the 24 h Air Quality Guideline set by World Health Organization to protect human health.  Such high levels are usually seen only in extremely polluted cities in India and China during pollution episodes.

There are several ways people are advised to act to limit personal exposure to pollution during Australian wildfire seasons. These include advice to stay indoors with windows and doors closed, limit physical exercise and other activities outdoors, ensuring access to regular medication such as asthma medicine, and checking in on older neighbors. The problem is that many of these advices are developed for short-term and more localized events and become impractical in the long run (Vardoulakis et al., 2020).

In a national survey, carried out in January 2020 among a representative sample of more than 1000 Australians, more than a quarter of the respondents reported that they had suffered breathing problems and illness because of the wildland fire smoke (The Australian Institute, 2020). When the current fire season finally comes to an end and the necessary health registries and pollution data becomes available to researchers, the toll on human health can be further quantified. The question is whether such accounts, together with accounts of the other losses to Australian nature and society, might work as a motivator for more ambitious climate policies in Australia and elsewhere.

References

Analitis A, Georgiadis I, Katsouyanni K. Forest fires are associated with elevated mortality in a dense urban setting. Occup Environ Med 2012; 69: 158-62.

Andela N, Morton DC, Giglio L, Chen Y, van der Werf GR, Kasibhatla PS, et al. A human-driven decline in global burned area. Science 2017; 356: 1356-1362.

Boer MM, Resco de Dios V, Bradstock RA. Unprecedented burn area of Australian mega forest fires. Nature Climate Change 2020.

Bowman D, Williamson GJ, Abatzoglou JT, Kolden CA, Cochrane MA, Smith AMS. Human exposure and sensitivity to globally extreme wildfire events. Nat Ecol Evol 2017; 1: 58.

Lam SS, Waugh C, Peng W, Sonne C. Wildfire puts koalas at risk of extinction. Science  2020; 367: 750.

NSW Department of Planning, Industry and Environment, 2020. Daily Air Quality Data https://www.dpie.nsw.gov.au/air-quality/air-quality-concentration-data-updated-hourly/daily-air-quality-data

Sanderson BM, Fisher RA. A fiery wake-up call for climate science. Nature Climate Change 2020.

Sofiev M. Wildland Fires: Monitoring, Plume Modelling, Impact on Atmospheric Composition and Climate. Chapter 21 in Matyssek, R., et. al (eds.). Climate Change, Air Pollution and Global Challenges. Developments in Environmental Science, vol. 13. ISBN: 978-0-08-098349-3 ISSN: 1474-8177, Elsevier & Book Aid Intern., pp.451-474.  2013.

The Australian Institute, 2020. Polling – Bushfire crisis and concern about climate change. https://www.tai.org.au/sites/default/files/Polling%20-%20January%202020%20-%20bushfire%20impacts%20and%20climate%20concern%20%5Bweb%5D.pdf

Vardoulakis S, Jalaludin BB, Morgan GG, Hanigan IC, Johnston FH. Bushfire smoke: urgent need for a national health protection strategy. Med J Aust 2020.

Yu P, Xu R, Abramson MJ, Li S, Guo Y. Bushfires in Australia: a serious health emergency under climate change. The Lancet Planetary Health 2020; 4: e7-e8.