When the COVID-19 pandemic brought human activity to a standstill around the world in the first half of 2020, wildfire incidents also declined by more than 12%. A new study publishing October 9 in the Cell Press journal Cell Reports Sustainability reveals the complex role humans play in shaping global fire patterns, both as a source of fire and in helping keep fires in check. The researchers show that fire incidents decreased by more than 27% and 8% in forests and grasslands, respectively, suggesting that these ecosystems are particularly vulnerable to human-caused fires.
"The relationship between human activity and wildfire is very complex," says first author Jianghao Wang of the Chinese Academy of Sciences. "Traditionally, we've viewed humans only as a fire contributor, so COVID-19 gave us a unique opportunity to disentangle this relationship."
Around the world, human activity has been increasingly influencing wildfire patterns, not only by igniting fires through unattended campfires or discarded cigarettes but also by suppressing and managing fires. Wang and his team wanted to know whether that pattern changed during the pandemic, when lockdowns kept many people at home and dramatically reduced human outdoor activity.
The team analyzed satellite observations of fires, meteorological data, government lockdown policies, and mobility patterns across the globe. They compared fire activity during the first six months of 2020, when many countries imposed movement restrictions, with wildfire patterns from 2013 to 2019.
The researchers found that the slowdown in human activity in 2020 reduced global fire incidents by 12.3%. There were also smaller burn areas and lower carbon emissions compared to the historic average levels. But the number of incidents varied substantially from one region to another. For example, fire activity fell by 79% in Australia and nearly 23% in the United States. In contrast, Columbia saw a 31% increase in fire incidents and Honduras saw a 70% increase.
"These different trends highlight the role of human activities in both fire ignition and suppression," Wang says. He adds that the increase in some regions may be in part due to reduced fire-management activities during lockdowns. With fewer people monitoring and patrolling outdoor areas, fires may have gone undetected for longer or received delayed responses.
The researchers also investigated how much prescribed burns—deliberately set fires used to reduce fuel and prevent larger, more destructive wildfires—contributed to the overall decline in fire activity. They analyzed data from 12 countries with detailed records of prescribed burns. The countries included the United States and Canada, where prescribed fire is an important tool for managing wildfire risk.
They found that in 2020, the area treated with prescribed fire fell to about half the historical average. After accounting for this reduction in prescribed burning, overall fire incidents in the 12 countries still declined by more than 27% following lockdowns.
The effects were particularly pronounced in forests and grasslands, where fire incidents declined by more than 27% and 8%, respectively, suggesting that these ecosystems are particularly vulnerable to human-caused ignitions.
Based on their findings, the team suggests that in regions where human-caused ignition is a dominant driver of fire, strictly controlling fire use can help reduce fire incidence. But in places where human activity is relatively limited and fire-management resources are scarce, strengthening monitoring and patrols may be more important.
"Human activity can act as a double-edged sword when it comes to wildfire," Wang says. "Such duality suggests that fire management is not something that can be handled with a simple, one-size-fits-all approach. Human roles need to be considered in the context of each region."
