Climate change will increase wildfire risk and lengthen fire seasons

Wildfires pose a significant threat to both the environment and communities, causing widespread destruction and pollution. Effective forecasting and management of these natural disasters are crucial for minimizing their impact. A recent study, featured in the November edition of Earth’s Future, offers new insights into wildfire risk assessment.

In this collaborative research effort, experts from the Desert Research Institute (DRI), Argonne National Laboratory, and the University of Wisconsin-Madison have joined forces to evaluate future fire risks. The study examines the four primary fire danger indices utilized across North America, which are essential tools for predicting and managing wildfire risks.

The researchers analyzed the relationship between these indices and the actual size of wildfires recorded from 1984 to 2019. Their findings contribute valuable scientific knowledge that can aid fire managers in understanding wildfire risks and making informed decisions about resource allocation.

The study delves into the projected changes in wildfire risk under future climate scenarios, revealing an increase in both fire potential and the length of the wildfire season due to climate change.

Dr. Guo Yu, an assistant research professor at DRI and the study’s lead author, emphasized the importance of using multiple fire danger indices to evaluate fire risk in the contiguous United States. While previous research has often focused on a single index, this study aims to provide a comprehensive assessment of how climate change might affect wildfire risk and how it correlates with the actual size and characteristics of wildfires.

Wildfire risk under future climate scenarios

Fire danger indices are critical tools that incorporate weather conditions and vegetation dryness to gauge fire risk. The most commonly used indices in North America include the USGS Fire Potential Index, the Canadian Forest Fire Weather Index, and the Energy Release Component and Burning Indices from the National Fire Danger Rating System.

The researchers analyzed satellite remote sensing data from 1984-2019 for over 13,000 wildfires, excluding controlled burns. Their findings indicated a strong correlation between higher wildfire risk and larger wildfire sizes, particularly over extensive areas.

By integrating these indices with future climate projections, the study predicts a significant increase in extreme wildfire risk—an average of 10 additional days across the continental U.S. by the century’s end, primarily due to rising temperatures.

Regions like the southern Great Plains are expected to face over 40 extra days per year of extreme wildfire danger. Conversely, a few areas, such as the Pacific Northwest coast and the mid-Atlantic coast, might experience a shorter annual wildfire risk season due to increased rainfall and humidity.

In the Southwest, the extreme wildfire season could extend by more than 20 days annually, with the majority occurring during spring and summer. This research provides valuable insights for fire managers to better understand and prepare for future wildfire risks.

How has risk increased?

The University of East Anglia explains in a statement that climate models suggest the frequency of fires in some areas of the planet, such as the Amazon or the Mediterranean, is unprecedented compared to recent historical climate due to human-induced global warming of about 1.1 °C in modern times.

These same models also reveal that the likelihood of severe wildfires in the western United States, Australia, and Canada is "significantly higher" in recent times. The most serious thing is that "this will be the case in practically all regions of the world if global temperatures reach 2-3 °C of warming according to the current trajectory," they warn.

Lead author Dr Matthew Jones, from UEA's Tyndall Center for Climate Change Research, 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 fires.

"Clarifying the link between wildfire trends and climate change is critical to understanding wildfire threats in future climates. Societies can drive or offset rising fire risks due to climate change, and regional actions and policies certainly can be important in preventing forest fires or reducing their severity.

"Ultimately, however, we will fight the tide of rising fire risks as the world gets hotter. Redoubling efforts to reduce greenhouse gas emissions and limit warming to less than 2°C is the most effective thing we can do to avoid the worst global wildfire risks.

How does human activity influence?

The results of the study show that the duration of the annual fire season has increased by 14 days per year in the period between 1979 and 2019. On the other hand, the fire climate has also grown exponentially in most areas of the planet since the 1980s.

If global warming increases to 2°C, the elevated risk of catastrophic wildfires will also occur in the boreal forests of Siberia, Canada, and Alaska and in the temperate forests of the western US.

"Wildfires can have massive detrimental impacts on society, the economy, human health and livelihoods, biodiversity, and carbon storage. These impacts are typically magnified in the case of wildfires," the author explains director, Dr. Matthew Jones, of the Tyndall Center for Climate Change Research at UEA.

The researcher highlight that human activity has important regional effects on the frequency of wildfires in a constantly warming world. "For example, they have increased fire ignition and reduced the natural resilience of some ecosystems to fire, especially in major areas of tropical deforestation in the Amazon and Indonesia."

However, humans have also been able to reduce the spread of wildfires in prone areas by "converting land to agriculture and fragmenting natural vegetation." A fact that has been seen in savannah grasslands in Africa, Brazil and in northern Australia.

• The length of the annual fire season has increased by 14 days per year (27%) during 1979-2019 on average globally and the frequency of extreme fire days has increased by 10 days per year (54%) during 1979-2019 on average worldwide.

Key findings of the analyzes include

• Fire weather has increased significantly in most regions of the world since the 1980s. The increases have been particularly pronounced in western North America, the Amazon, and the Mediterranean. Fire climate has already emerged beyond its natural variability in the Mediterranean and Amazon due to historical warming.

• At 2°C, this will also occur in the boreal forests of Siberia, Canada, and Alaska and in the temperate forests of the western US. At 3°C, virtually every region of the world will experience unprecedented fire weather.

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• Worldwide, the area affected by fires dropped by a quarter or 1.1 million km2 from 2001-2019, with most reduction occurring in African savannas where 60-70% of annual fires occur. Local human interventions and lower grassland productivity in tropical savannas during dry wet seasons attribute to this decrease.

• Large increases in the area burned have been seen elsewhere, especially in temperate and boreal forests. For example, the area burned by fire has increased by 21,400 km2 (93%) in the forests of eastern Siberia and by 3,400 km2 (54%) in the forests of western North America (Pacific Canada and US combined).

The study evaluated 500 previous research papers and conducts a new analysis of state-of-the-art data sets of satellite observations and models. It includes analyzes of trends in fire climate and burned areas for world regions covering all countries, continental-scale macro-regions, and regional ecosystems key to fire activity or impact.

We examine future changes in fire climate for these same regions in policy-relevant warming increments of 1.5°C, 2°C, 3°C, and 4°C. This provides insights into how the success or failure of climate policies correspond to the risks of forest fires that we will have to live with in the future.

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