Wildfire study tracks regional timing shifts
A new study has found that climate change is changing the timing of wildfire seasons across North America, with earlier fire seasons in northern forests, limited change in prairie regions and later activity in parts of the western United States and California.
The research, published in Geophysical Research Letters, examined wildfire activity across 18 ecological regions using burn area data collected between 2001 and 2020 from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua and Terra satellites.
Researchers combined the satellite data with environmental variables including temperature, precipitation, soil moisture, vegetation conditions, wind speed and lightning potential.
The analysis found that ecosystems are responding in different ways, with boreal and taiga forests across Alaska, Canada and parts of the Great Lakes region showing wildfire seasons that are shifting earlier in the year.
The study links that change to earlier snowmelt and faster drying of vegetation, which exposes flammable fuels sooner in spring.
It also found that boreal ecosystems are especially sensitive to atmospheric dryness, which was identified as the main driver of wildfire activity across several fire regimes.
Hongliang Zhang, environmental scientist at Fudan University in China, said: “It’s very region-specific.”
Wildfire seasons extend later in western regions
The study found that Mediterranean-type climates and desert regions in the western United States are seeing fire seasons that continue later into the year.
In California and the warm desert Southwest, increased late-season burning is pushing wildfire activity further into autumn and early winter.
The research links those patterns to prolonged drought conditions and changes in vegetation dynamics that increase fuel availability later in the year.
Prairie ecosystems and humid forest regions including the Appalachian Mountains and the southeastern United States showed only limited shifts in wildfire timing.
Researchers said these regions may be more stable because of stronger precipitation influences and different vegetation structures.
Wildfire projections point to further seasonal change
The researchers also used climate model projections to assess how wildfire seasons may change in future decades.
Under a high-emissions climate scenario, the study projects that boreal wildfire seasons could begin around a week earlier on average.
Some northern regions could shift by more than three weeks.
California’s wildfire season could extend by more than a month beyond the traditional June-to-October window, and desert regions in the western United States may also see later seasonal expansion.
The source material also states that the modelling framework could be used to assess vegetation change, along with human activity, in wildfire ignition.
According to the source material, about 85% of wildland fires in the United States are caused by human actions, including arson or unattended campfires.
Zhang said: “That model is really good at predicting wildfire.
“So now we want to predict the emissions of wildfire to the atmosphere.”
The study concludes that climate change is reshaping the seasonal distribution of wildfire activity across North America in ways that differ sharply between ecosystems.