Environmental Science
How Wildfire Regimes Are Changing with Climate Change
Quick fact
In the western United States, the average annual area burned by wildfires has increased by more than 400% since the 1970s, largely due to climate-driven drying.
Why this is interesting
You've heard that wildfires are getting worse, but what exactly is changing about them?
Read the full explanation
Understanding How Wildfire Regimes Are Changing with Climate Change
A wildfire regime describes the pattern of fires in a region—how often they occur, how large they get, and how intensely they burn. Climate change is fundamentally altering these patterns. Warmer temperatures cause snow to melt earlier and soils to dry out faster, creating longer fire seasons that now start earlier and end later. In many regions, droughts are becoming more severe, turning vegetation into tinder. As a result, fires are more frequent and spread faster. The same areas that used to see small, low-intensity fires now experience massive, high-intensity blazes. This shift is not uniform—some places get wetter and see fewer fires—but globally, the trend is toward more extreme fire activity.
A deeper explanation
The mechanism behind these changes involves several feedback loops. Higher temperatures increase the vapor pressure deficit (VPD), which means the air sucks moisture from plants and soils more aggressively, making fuels drier. Drier fuels ignite more easily and burn with greater intensity. Climate change also alters weather patterns, such as promoting high-pressure ridges that cause heatwaves and wind events that fan flames. In boreal forests, warming leads to more lightning-ignited fires and permafrost thaw, which releases stored carbon and further accelerates warming. Additionally, insect outbreaks (e.g., pine beetle) boosted by milder winters kill trees, adding more dry fuel. These interactions create a self-reinforcing cycle: more fires release more greenhouse gases, which worsen climate change, leading to even more fire. Understanding these regime shifts is essential for adapting fire management strategies (e.g., prescribed burns, defensible space) and for predicting future carbon emissions from fires.