Where there is fire, there is smoke

Abstract

In his In Depth News story “Scientists aim to smoke out wildfire impacts” (1 June, p. 948), W. Cornwall discusses wildfire-generated smoke and the associated large quantities of particulate matter. We agree that research on smoke demands more sustained scientific attention, particularly given its impacts on human communities [e.g., (1)]. However, not all fires are created equal in terms of their (natural or deliberate) origins, the amount of biomass they consume, and the amount of smoke they generate as a result.

High-intensity wildfires (those exceeding 200,000 kW/m2) in very high biomass forests may consume 9 to 14% of the biomass (burning green parts of living trees but often leaving dense wood) or 40 to 58 tons per hectare (2). This is substantially less than half of the 140 to 450 tons of biomass per hectare consumed when logging slash (i.e., dense waste wood) is burned after logging operations in these same kinds of forest (3, 4).

Moreover, such logging burns consume at least 10 times as much biomass as hazard reduction burns designed to reduce wildfire risk (5). The smoke generated from logging therefore represents a substantial form of industrial pollution, but it is not treated as such. Beyond improving efforts to quantify the chemical composition of smoke and its long-term impacts on human health, there is an urgent need to examine the problem in a more holistic manner. This demands far more careful consideration of the origins of smoke, the relative amounts of smoke originating from different kinds of fires, and the forest and land use policies that generate smoke (and might reduce it).