Wildfire risk spans continents, from the eucalyptus-laden hills of southeastern Australia to the chaparral of Los Angeles. The phenomenon is shaped by climate, vegetation and human behavior, making it hard to isolate any single driver. A research team led by Professor Jianghao Wang at the Chinese Academy of Sciences seized an unprecedented moment, the early-2020 COVID-19 lockdowns, to explore how a sudden, global reduction in human mobility altered fire patterns.
The scientists treated the pandemic-induced halt as a natural experiment, comparing satellite-derived fire detections during restriction periods with the same calendar weeks from 2013-2019. Mobility data derived from regional lockdown orders and mobile-phone location records defined the “stay-at-home” windows, while NASA’s Suomi NPP satellite, via its VIIRS sensor (375-meter resolution), supplied the count of active-fire hotspots. Because the sensor registers both wildfires and prescribed burns without distinction, the analysis reflects the net outcome of human ignition, suppression and management activities.
Quantifying the net effect of reduced mobility
When weather variables were statistically accounted for, the study uncovered a 12.3 percent decline in active-fire detections across locked-down regions during the first half of 2020. The impact varied markedly by ecosystem type. Forested areas experienced the steepest drop, 27.7 percent, while grasslands saw an 8.4 percent reduction. Shrublands, savannas and croplands showed no significant change, suggesting that human activity is a primary driver of fires in dense forest and open-grass settings, but less influential in other biomes.
Importantly, the 12.3 percent figure represents a **net effect**. Restrictions curtailed both the deliberate or accidental ignition of fires and the capacity of firefighters and land managers to suppress or contain them. As Wang emphasized, “The 12.3 percent is a net effect, not the share of fires caused by humans; opposing changes in ignition and suppression mean it does not capture the full magnitude of human influence.”
Regional anomalies: fires that surged despite lockdowns
While many locales recorded fewer detections, substantial increases emerged in parts of South America, southern Africa and northeast Asia. Notable spikes included a 31.4 percent rise in Colombia, 25.4 percent in India and an astonishing 70.7 percent surge in Honduras. The authors infer that weakened fire-suppression capacity (fewer patrols, delayed response times, and limited access to firefighting resources) likely contributed to these outliers, though direct field verification is lacking.
Analysis of mobility loss at a 0.5-degree grid level revealed two contrasting patterns. In countries with historically low fire counts, detections fell almost linearly as mobility dropped, indicating that human ignitions dominate there. Conversely, in fire-prone nations, detections initially rose with decreasing mobility before plateauing near a 27 percent increase, a trend the researchers attribute to reduced suppression rather than heightened ignition.
Prescribed burning and the limits of satellite observation
Prescribed (managed) burning, a common tool for reducing fuel loads, also declined during the lockdown year. In twelve nations where official prescribed-burn records exist, the area deliberately set ablaze fell by roughly 50 percent compared with the 2013-2019 baseline. Excluding zones with prescribed burns trimmed the overall fire-decline statistic from 45.3 percent to 27.8 percent, underscoring how management practices intertwine with observed fire activity.
The study’s reliance on mobile-phone mobility metrics introduces uncertainties, especially in remote rural regions with limited signal coverage. Moreover, the focus on the first half of each year may overlook seasonal fire peaks that occur later, such as those typical of the western United States. Nonetheless, Wang contends that the quasi-experimental design supplies robust associational evidence, even if it cannot claim the causal certainty of a controlled trial.
Overall, the findings argue against one-size-fits-all fire policies. In ecosystems where fire counts fell, reducing accidental ignitions and maintaining beneficial prescribed burns appear paramount. In contrast, regions that experienced surges may need to safeguard firefighting and monitoring capabilities during societal disruptions. Incorporating human behavior metrics into fire-risk models could improve future projections as climate and socioeconomic conditions continue to evolve.
