Wildfires are uncontrolled fires in wildland areas that significantly impact ecosystems and human communities. They consume vegetation, spread rapidly, and pose threats to natural landscapes and populated regions. These common global disasters can burn millions of acres, destroying homes and infrastructure.
Seasonal Patterns
Wildfire occurrences are highly seasonal, linked to periods of drought, high temperatures, and low humidity. In the Western United States, the fire season typically runs from May to November, with peak activity in summer. The U.S. wildfire season’s peak has shifted earlier, from August to July in recent decades. The Mediterranean Basin, including Greece, Italy, Spain, and Portugal, also experiences intense summer fire seasons, often in July and August.
Australia’s bushfire seasons vary by region. Southern Australia’s peak season is summer and autumn, while northern Australia is at risk during winter and spring. New South Wales and southern Queensland face their greatest danger from spring to mid-summer. These peaks are driven by dry vegetation accumulation after wet periods, followed by hot, dry, and windy conditions.
Geographic Hotspots
Wildfires are most common in regions with environmental conditions and vegetation types susceptible to fire. The Western United States, including California, Oregon, and Washington, is a hotspot where significant land burns annually. Canada also experiences extensive wildland fires, with over 15 million hectares burned in 2023. The Mediterranean Basin, encompassing Spain, Greece, and Italy, is frequently affected due to its dry summers.
Other areas prone to frequent wildfires include Australia and parts of South America, such as the Amazon. These hotspots often feature Mediterranean, arid, or semi-arid climates, and fuel types like chaparral, eucalyptus, and boreal forests. Wildfires can also occur in less expected places, such as parts of the Arctic.
Contributing Conditions
Wildfires require fuel, heat, and oxygen to ignite and spread. Environmental factors contributing to their prevalence include prolonged drought, high temperatures, low relative humidity, and strong winds. These conditions dry out vegetation, turning trees, shrubs, and grasses into highly flammable fuel. The accumulation of this dry vegetation, known as fuel load, directly influences fire intensity and spread.
Human activity is a significant ignition source for wildfires. Nearly 90% of U.S. wildfires are human-caused, through actions like unattended campfires, discarded cigarettes, equipment malfunctions, and arson. Sparks from power lines and agricultural practices like slash and burn clearing also contribute. While natural causes like lightning strikes can start fires, human negligence is a predominant global factor.
Future Outlook
Climate change influences wildfire timing and location by creating warmer, drier conditions. Rising global temperatures, altered precipitation patterns, and increased extreme weather events are lengthening fire seasons and intensifying fires. The Western U.S. wildfire season has extended by about three months compared to previous years. Projections indicate an average annual 1°C temperature increase could raise the median burned area by as much as 600% in some forest types.
The risk of extreme wildfires is projected to surge globally, with anticipated increases of up to 14% by 2030, 30% by 2050, and 50% by the century’s end. Wildfires are expected to become more frequent and intense, even in regions not traditionally high-risk, such as parts of the northern U.S. and central Europe. The combination of fuel buildup and warmer, drier conditions increases the potential for extreme fire behavior.