Globally, wildfires in the 2019/2020 season have been extremely severe, affecting countries across the globe, at all latitudes. From fires in the northern hemisphere within the Arctic Circle in Siberia, to fires in the equatorial Amazon rainforest, and the Australian bushfires in the southern hemisphere – they have had devastating effects. Whilst most of these areas experience annual fire seasons that ravage the landscape and cause a wide range of socioeconomic problems, this last fire season has been undoubtedly exacerbated by climate change, with many temperature and land area records being broken. Climate change must be considered as a key contributing factor when governments and super-national bodies mobilise initiatives to mitigate wildfires.


The Californian wildfires of 2019, like many others, captured global media attention. However, they were unique in that they took place in a densely populated area, blessed with significant resources. The state had a population of 39.51 million in 2019, approximately 3 million more than the population of Canada.

The wildfires, as with any natural hazard, were caused by several factors. Early in the year, an unusually high volume of precipitation resulted in excess growth of vegetation, which in autumn and winter created an unusually high dry biomass that acted as fuel for the fires. Additionally, two seasonal winds, the Diablo wind and the Santa Ana wind contributed significantly, increasing the risk of an intense wildfire season. The Diablo wind is caused by high pressure forming over the Great Basin, and the jet stream being present north of this, pushing hot winds from the mainland offshore towards the coast of California. These high-pressure winds are forced over the Sierra Mountains, compressing the air, and reducing the humidity. The winds then cascade into the Central Valley, are further heated and then flow over the coastal mountains, heating again and becoming less humid in the process. Wind speed increases to as much as 40 mph, posing a risk to overhead power lines. The high wind speed also enhances up draughts causing and generated by fires. The Santa Ana winds are different in that they are Katabatic, and form as a result of a high-pressure system forming over the Great Basin and Mojave Desert. Air masses are forced through the canyons and mountain passes of the Transverse Ranges, and as they descend, warm adiabatically, at a rate of 10C for every 1000m they descend. This results in strong, very warm, and very dry winds blowing offshore (Gong, 2019). Both these winds cause and exacerbate fires later in the season, between October and December, in part by drying the unique plant community that swathes much of mediterranean California, called Chaparral. The 7,860 wildfires of 2019 burned 259,823 acres of land, killing 5 people and injuring 22. 732 structures were destroyed, and the total cost of the fires was $163m (CalFire, 2019) The effects of the fires were numerous and severe. Short term effects included a power shutdown to 800,000 inhabitants, as authorities tried to reduce the threat that overhead powerlines presented to starting new fires (Morris, 2019). Pollution generated by the fires also resulted in respiratory complications and severe symptoms in medically vulnerable people. Indeed, particulates created from the destruction of structures during a wildfire can be particularly harmful, and urgent research is being and has been undertaken by the University of California and Stanford University to determine the long-term effects of the pollutants on health. Globally, 4 million people a year die directly from pollution, and the concern is for a higher number of fatalities occurring in California. The researchers at Stanford University suggested the pollutants generated by wildfires impair the immune system (M Prunicki, 2019), but more research is necessary to gain a better understanding of the issue. Resultant ash also chokes riverine systems, both threatening the water supply of the state, and destroying delicate habitats. The acute water crisis that California faces as a result of the diminishing snowpack on the Sierra Nevada, is only compounded by the water needed for fighting the fires, along with the effects the fires have on the hydrological system including the combustion of soil and the water that it retains.

Figure 1. The Santa Ana Wind Paths


The Siberian wildfires of 2019 and 2020 were exceptionally severe and affected an area that is not usually associated with scorching temperatures and expansive fires. The extreme wildfires were again caused by several, interrelated factors, with climate change being the most significant. The fire season of 2019 was on average 10C warmer than the summer average for Siberia, and this year has already seen the average temperature being over 5C warmer than the yearly average. In this region the melting of permafrost releases methane and other greenhouse gases which act as a positive feedback loop, in turn increasing atmospheric temperatures. Climate change also increases the intensity and frequency of heat waves, which are caused by a column of downward moving air that traps and compresses air near the surface. In the summer this is exacerbated by the ‘midnight sun’ of the Arctic Circle, which allows insolation across the entire day. A heat wave in June 2020, resulted in temperatures exceeding 37C within the Arctic Circle in Russia, with Verkhoyansk recording 100.4 F, believed to be the highest ever temperature recorded in the Arctic Circle. The winter of 2019, being the hottest on record  (The Moscow Times, 2020), resulted in a low volume and duration of snow cover, which reflected solar radiation, reducing temperatures. The low water content of the soil by spring also prevented evaporation from occurring, which further cooled air. The high temperatures, and low humidity dried out vegetation which became fuel for fires, which were then fanned by strong winds.

The fires of 2019 burned mainly in the Russian region of Krasnoyarsk Krai, and ended up destroying 7,900,000 acres of land, mainly taiga forests (The Washington Post, 2019). The extensive smoke released disrupted air travel in the region, and created hazardous conditions for aerial firefighting (Agence France-Presse, 2019), and ultimately created hazardous levels of pollution in many major Russian cities, eventually reaching the west coast of America. Current wildfires have received little media attention but are estimated to have already burnt millions of acres. The long-term effects of the wildfires in such a fragile ecosystem will be devastating. The burning of taiga forests releases huge volumes of carbon dioxide which contribute to the ‘Greenhouse Effect’, but the ability of the biome to sequester carbon dioxide is greatly reduced in the future. Another serious long-term effect of wildfires is that they expose and further heat permafrost, a layer of frozen ground below the active layer. This is damaging in two main ways; firstly, melting permafrost releases greenhouse gases such as methane that are generated by microbes decomposing the frozen organic matter stored in the permafrost, often in thermokarst lakes as ‘abrupt thaw’ (K Walter-Anthony, 2018). Secondly, the ground subsidence caused by melting permafrost damages valuable and important infrastructure. For example, the Norilsk Oil Spill in May 2020, was a result of a storage tank rupturing due to subsidence and released more than 17,500 tonnes of diesel oil into an area of 350km^2 (Skarbo, 2020). Permafrost melting was the sole cause of the oil spill, which having been initially contained, has now spilled into Lake Pyasino, and threatens a river which drains into the Arctic Ocean. This example demonstrates the multiplier effects wildfires can have at a local, national and international level.

Figure 2. The Development of the Wildfire Complexes in Siberia, July 2019


The Australian wildfires of 2019 and 2020 captured global media attention like no others and set several records and precedents. The fires were beyond the normal fire season in terms of intensity, and were caused directly, like most other wildfires by thunderstorms and the associated lightning strikes. Climate change increased the intensity of the wildfires, and 2019 is a year that set numerous records in terms of temperature in Australia (Garnaut, 2008). For example, 2019 was both Australia’s hottest and driest on record, with its hottest ever temperature recorded at 41.9C.  December was also the hottest one record in 2019.

In the 2019/2020 fire season, 46,000,000 acres of land were burnt, far exceeding both the Californian and Siberian fires (Noble, 2020). More than 9350 buildings were destroyed, 451 people were killed (The Daily Telegraph, 2020) (Nicolas Borchers Arriagada, 2020), and at some points, firefighters were fighting a complex front more than 6000km long. The University of Sydney estimated over 1 billion animals were killed, many of which were species endemic to Australia (Dickman, 2020). The total cost of the fires is expected to exceed $3 billion. Valuable ecosystems unique to Australia were destroyed, including wet eucalypt forests, swamps, and rainforests, with high numbers of endemic plants and associated species. It is thought likely that as many as 100 endangered species have been driven to extinction (CBS News, 2020), with many more likely to be pushed to extinction as a result of starvation and predation following the fires. The generated a significant amount of particulate pollution and greenhouse gases, with NASA estimating the fires produced a total of 306,000,000 tonnes carbon dioxide (Lee, 2019). The particulate count in Sydney at one point measured 734 micrograms, equivalent to 37 cigarettes (BBC News, 2019). The pollution also became an international issue, as particulates were deposited on glaciers in New Zealand, caused hazy conditions in Auckland, and was carried in the atmosphere across the Pacific to Chile.

Wildfires in the 2019/2020 season, affected countless counties around the world, not just Russia, the USA, and Australia, but also in Spain, Italy, the UK, Greenland and Brazil to name only a few. They exposed and exacerbated many important socio-economic and environmental issues that continue to plague countries at all levels of development, including water security, infrastructure development, health, habitat loss and biodiversity. In order to resolve these issues, we must consider the interdependent relationship with wildfires; to tackle them wildfires must be mitigated, both in terms of their magnitude and frequency. However, whilst all these issues vary from country to country, and even between states in some nations, one common denominator that intensifies wildfires, and the associated effects, is clearly climate change. Whilst national and international aid packages and privately finance is used to help address the short-term effects of wildfires, extensive research must be properly funded in order that we may continue to effectively develop our understanding of the relationship between climate change and wildfires. If we do nothing, we will continue to – inadvertently or otherwise – fan the flames and they will burn until the damage is irrevocable.

Figure 3. Extent of the Pollution Generated by the Australian Wildfires, NASA


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Lee, H. (2019). “Bushfires Release Over Half Australia’s Annual Carbon Emissions”. Time Magazine.

M Prunicki, X. Z. (2019). “The impact of prescribed fire versus wildfire on the immune and cardiovascular systems of children”. European Journal of Allergy and Clinical Immunology, 143(2).

Morris, J. (2019). “PG&E: Massive power shut-off to hit 800,000 customers, could extend nearly a week”. San Francisco Chronicle.

Nicolas Borchers Arriagada, A. J. (2020). “Unprecedented smoke‐related health burden associated with the 2019–20 bushfires in eastern Australia”. Medical Journal of Australia.

Noble, F. (2020). 9News. Accessed (June 2020)

Skarbo, S. (2020). “State of emergency in Norilsk after 20,000 tons of diesel leaks into Arctic river system”. The Siberian Times.

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