The past decade has seen devastating wildfires in forest areas around the world, with far-reaching impacts. These extreme fire years – defined as periods with large-scale regional fires and Exceptional burned areas – have received increasing scientific and public attention. Examples include Australia in 2019–2020, the western US in 2020, and Canada in 2023. Although global burned area has declined overall in recent decades due to land-use changes, the world’s forest biomes have seen increases in fire activity and carbon emissions.

Characteristics of extreme fire years

Extreme regional fire years are often associated with exceptionally high values Fire Weather Index (FWI), which quantifies fire risk based on meteorological conditions. The study showed that these years typically coincided with an extreme FWI that occurs once every 15 years. A review of case studies, including the 2020 fires in the western US, 2023 in Canada, and 2019–2020 in southeastern Australia, confirmed that FWI metrics were highest during these events in the period 1979–2023.

During extreme fire years, the following were recorded:

• Fourfold increase in the number of large fires.
• Five-fold increase in carbon emissions from fires compared to non-extreme years. Specifically, carbon emissions from fires in southeastern Australia in 2019-2020 were comparable to the sum of all other years in the period 2002-2023.
• In most ecoregions, the burned forest area in extreme years was at least five times greater than the average in non-extreme years.

The impacts of these extreme fire years are widespread and include hazardous air quality, direct loss of human life and infrastructure, economic losses, and widespread ecosystem impactsFor example, wildfires in Canada in 2023 led to the evacuation of more than 230,000 people.

Climate change as a major factor

Research clearly shows that Human-caused climate change significantly increases the likelihood of extreme regional fire years in the world's forested areas. Compared to the quasi-pre-industrial climate (1851–1900), years with such extreme FWI metrics are 88 – 152 % more likely in the current climate (2011–2040). The most significant increase in risk is observed in temperate and Amazonian forests. Overall, the probability of extreme FWI metrics occurring once every 15 years has doubled (hazard ratio ≥ 2) for 46–65 % forested areas of the world.

The main factors contributing to this increase are: extensive temperature increase and decrease in surface relative humidity, leading to drier fuelThe sources report that while long-term droughts were not as closely linked to extreme fire years as FWI metrics during the fire season, extreme fire years in tropical biomes often occurred in places where deforestation and agricultural burning were associated with moderate to severe drought conditions.

Other contributing factors and challenges in fire management

In addition to climatic factors, local and regional factors also influence fire dynamics. anthropogenic factorsA century-long history of fire suppression and agricultural land abandonment has led to deforestation in some regions. increasing the quantity and continuity of fuel, which contributes to the formation of larger and more energetic fires.

Traditional approaches to fire management, which focus on fighting individual fires, are increasingly ineffective. Regional extreme fire years have demonstrated the unsustainability of this strategy, as Firefighting resources are overloaded by the high number of large fires burning simultaneously and demand exceeds supply.

The need for proactive adaptation measures

While efforts to mitigate climate change by reducing greenhouse gas emissions remain crucial, adaptation strategies will be vital to improving preparedness and resilience in risk regions. These strategies include:

• Proactive fuel reduction at a local scale to reduce fire intensity and weaken climate sensitivity to fires.
• Fire prevention efforts in order to minimize human-caused fires.
• Adaptation measures to minimize direct and indirect impacts of fires on communities and ecosystems.

With fire seasons lengthening and resources limited, it is essential a shift in fire management tactics from a reactive and suppressive approach to a more proactive approach, which includes restoring beneficial fire regimes and preparing landscapes and communities to withstand fires and mitigate catastrophic impacts. Climate change is increasing the likelihood of extreme fire years, requiring urgent, comprehensive and proactive measures. Spring

The study was published in magazine Nature