New research shows how wildfire risk is increasing globally as a result of climate change, but also how human actions and policies can play an important role in regulating regional impacts. An international team of researchers led by the University of East Anglia (UEA) in the UK conducted the study, which found that anthropogenic climate change is a ‘push’ factor that increases the risk of wildfires globally.
Fire weather, or hot, dry conditions conducive to wildfires, is becoming more common as a result of climate change, increasing the risk of large wildfires by making landscapes more susceptible to burning more frequently and severely. The effects of climate change on fire risk are expected to worsen in the future, with each additional degree increasing the risk of a wildfire.
Climate models indicate that the frequency of fire weather conditions in some world regions, such as the Mediterranean and Amazonia, is unprecedented in the modern period compared to the recent historic climate, owing to human-induced global warming of around 1.1°C. More importantly, if global temperatures continue on their current trajectory, this will be the case in virtually all world regions.
Climate models have also revealed that historical climate change increased the likelihood of some of the most recent and devastating wildfires in the western United States, Australia, and Canada.
The article, published in the journal Reviews of Geophysics, involved scientists from UEA, Swansea University, the University of Exeter and Met Office in the UK, CSIRO Climate Science Centre in Australia, together with colleagues from the US, Germany, Spain and the Netherlands.
It explores the relationship between fire trends — past, present and future — and a range of controls on fire activity, including climate but also human activity, land use and changing vegetation productivity, which have with important impacts on the ignition of wildfires and their spread across landscapes.
Wildfires can have massive detrimental impacts on society, the economy, human health and livelihoods, biodiversity and carbon storage. These impacts are generally magnified in the case of forest wildfires.
Dr. Matthew Jones
Lead author Dr. Matthew Jones, of the Tyndall Centre for Climate Change Research at UEA, said: “Wildfires can have massive detrimental impacts on society, the economy, human health and livelihoods, biodiversity and carbon storage. These impacts are generally magnified in the case of forest wildfires.
“Understanding wildfire threats in future climates requires elucidating the link between forest wildfire trends and climate change. Societies can either push with or push against the rising risks of fire caused by climate change, and regional actions and policies are certainly important for preventing wildfires or reducing their severity. However, as the world continues to warm, we will be fighting a rising tide of escalating fire risks. Increasing our efforts to reduce greenhouse gas emissions and keep warming below 2°C is the most effective thing we can do to avoid the worst risks of wildfire on a global scale.”
The authors highlight that humans have important regional effects on wildfire activity in a warming world. For example, they have increased fire ignitions and reduced the natural resilience of some ecosystems to fire, most notably in major tropical deforestation zones of Amazonia and Indonesia.
Humans, on the other hand, have reduced the spread of wildfire through naturally fire-prone landscapes by converting land to agriculture and fragmenting natural vegetation, as seen in recent decades in savannah grasslands in Africa, Brazil, and Northern Australia. They can also reduce unwanted ignitions or use firefighting to suppress wildfires, as has been done in the forests of the United States, Australia, and Mediterranean Europe in the past. However, the authors warn that this could have unintended consequences in areas where fire is a natural component of ecosystem function.
For example, during the twentieth century, policies that aggressively prohibited fire from the western US landscape resulted in forests that are now overburdened with vegetation fuels, contributing to more severe wildfires during recent droughts. Low-intensity fires used during safe weather conditions are increasingly seen as an important tool for keeping fuels under control while also facilitating natural ecosystem functions.
Key findings from the analyses include:
- The length of the annual fire weather season has increased by 14 days per year (27 percent) on average from 1979 to 2019, and the frequency of days with extreme fire weather has increased by 10 days per year (54 percent) on average from 1979 to 2019.
- Since the 1980s, fire weather has increased significantly in most parts of the world. Increases have been most noticeable in western North America, the Amazon, and the Mediterranean. Due to historical warming, fire weather has already surpassed its natural variability in the Mediterranean and Amazonia.
- At 2°C, this will also be true in the boreal forests of Siberia, Canada, and Alaska, as well as the temperate forests of the western United States. At 3°C, virtually every region on the planet will experience unprecedented fire weather.
- Between 2001 and 2019, the global area burned by fires decreased by roughly one-quarter, or 1.1 million km2. The majority of the reduction (590,000 km2) has occurred in African savannahs, where 60-70 percent of the area burned by fire occurs annually. Local/regional human impacts, combined with lower grassland productivity during (increasingly drier) wet seasons, have reduced the area burned by fire in tropical savannahs.
- Significant increases in burned area have been observed elsewhere, particularly in temperate and boreal forests. For example, the area burned by fire in east Siberian forests has increased by 21,400 km2 (93 percent) and in western North American forests by 3,400 km2 (54 percent) (Pacific Canada and US combined).
Co-author Dr Cristina Santín, from Swansea University and the Spanish National Research Council, added: “Despite the fact that weather conditions promoting wildfire have already increased in nearly in every region the globe and will continue to do so, human factors still mediate or override the climatic ones in many regions.
“We hope this research helps to resolve the entrenched and conflicting views on climate change versus land management being the root cause of these catastrophic fires.”
The study reviewed 500 previous research papers and re-analyzed state-of-the-art datasets from satellite observations and models. It includes analyses of trends in fire weather and burned area for all countries, continental-scale macroregions, and key regional ecosystems for fire activity or impact.
Future changes in fire weather are examined for these same regions at policy-relevant warming increments of 1.5°C, 2°C, 3°C, and 4°C, providing insight into how the success or failure of climate policies correspond to the risks of wildfire we will have to live with in the future.
