Satellite counts tie the 2020 lockdowns to 12.3% fewer fires worldwide

The control in the Cell Reports Sustainability paper by Jianghao Wang of the Chinese Academy of Sciences and colleagues ^[3] is seven ordinary years. Fire activity in the first six months of 2020 was compared with the pattern from 2013 to 2019, using satellite fire observations, meteorological data, government lockdown policies and mobility records ^[4]. The mobility records make the pandemic usable as an experiment, because they show how far movement actually fell in each country ^[4]. Burned area and carbon emissions also came in below historical averages, according to phys.org's account of the study ^[5].

I think the prescribed-burn check is the most careful step. A lockdown cancels managed fires along with careless ones. If cancelled controlled burns had caused most of the drop, it would say little about accidental ignition. Prescribed fire did fall: in the 12 countries with detailed records, including the United States and Canada, it covered about half its usual area ^[8]. The decline left after that adjustment is more than twice the global 12.3% ^[2][13]. The two figures cover different sets of countries, so the gap between them is not an effect size on its own.

The case for suppression comes from the countries where fires rose. "These different trends highlight the role of human activities in both fire ignition and suppression," Wang said ^[15]. He puts the rises down partly to reduced fire management. His reasoning is that with fewer people out watching and patrolling, a fire could have burned unnoticed for longer, or the response to it could have come late ^[14].

The thing this doesn't tell you is how much of the rise in Colombia and Honduras came from thinner patrols. Phys.org's account does not include patrol records, response times or the baseline fire counts behind the percentages, so a 70% rise ^[7] could mean a few extra fires or a great many. Weather data went into the analysis ^[4]. That matters most in these two countries, because a dry season alone could push a fire count up.

Wang described the pandemic as a chance to test an old assumption. "Traditionally, we've viewed humans only as a fire contributor, so COVID-19 gave us a unique opportunity to disentangle this relationship," he said ^[11]. The team's advice splits along the same line as the data. Where people cause most ignitions, they suggest strictly controlling fire use. Where human activity is limited and fire-management resources are scarce, they suggest stronger monitoring and patrols ^[10]. "Human roles need to be considered in the context of each region," Wang said ^[12].