On Saturday morning, Donald Trump tweeted about the wildfires currently burningin both Northern and Southern California:

It’s not very clear what he’s talking about, but we can hazard a guess. His administration, through its secretaries of agriculture and the interior, seems to equate “forest management” with logging. If that is what Trump is saying—that California has fires because it hasn’t removed enough trees—the tweet is written either in ignorance or misdirection. Logging is more often a cause of fires than a cure. Besides, the current California fires are not even in forests.

So is there anything to the argument that differently managing the land would affect fire? That’s complicated.

Begin with fire. While we imagine (and model) landscape fire behavior as a physical event, unlike floods and hurricanes, it is a creation of the living world. Tornadoes and tsunamis can occur without a particle of life present; fire cannot. It literally feeds on biomass, behaving more like a plague of locusts than an ice storm. We can’t control the surface ocean that powers hurricanes or the shifting crustal plates that cause earthquakes. We can, within limits, modify the energy source of fire.

Controlling fuel is fundamental to any strategy of fire management. It’s what wildland firefighters do when they build fire lines—a sort of waterless moat around a fire—by removing a strip of vegetation. Depending on the flames, a fire line might be the width of a shovel or as wide as a football field. If the fire is spreading by embers riding winds like the Santa Ana, the fire might burn until it reaches the Pacific Ocean. Big wildland fires are contained by burning out swathes of fuel in advance of the oncoming flames. That’s one of many differences between wildland and urban fire. (We no longer dynamite or torch city blocks to deprive fire of fuel, as used to happen as late as 1906 when San Francisco burned.)

Likewise, fire management at a landscape scale aims to control the character of fire by altering the conditions under which it burns, which in practical terms means addressing the fuels it feeds on. We can’t level mountains, banish winds, or stop all ignitions. But we can modify the vegetation by how we live on the land. We can add fuels, we can reduce fuels, we can rearrange fuels.

We’ve done all that, sometimes deliberately, often without much attention to how fire will read the result. Every region, every subregion, has its own story of fire reorganized by its history of land use. California’s fires are as monumental as its mountains and winds, and tweaking the vegetation can work only on the margins, though it’s on those margins where people live.

Controlling combustibles is a major reason we halted the routine conflagration of cities that afflicted America’s cities up to a century ago. Until then, towns burned as often as the surrounding countryside since both were made of the same materials and experienced the same drought and winds. In principle, a similar logic might apply to our rural and wild landscapes if we could agree on what we wanted and how to achieve it. Proper tinkering, many observers think, might allow us to promote the good fires we want and prevent the bad fires we don’t.

For members of the Trump administration, this reasoning leads to “forest management,” which they seem to equate with chain saws. They argue that big-tree logging can be a benign (and profitable) surrogate for fire. But while all fuel is biomass, not all biomass is available as fuel. What fire wants is particles with a lot of surface relative to mass; it wants what a campfire or hearth fire wants. If you wish a fire to flash and roar, put in pine needles, dry grass, and kindling. Add a freshly cut green log and the fire will go out.

Which is to say, logging and burning do different things. Logging physically removes biomass; fire chemically changes it. Logging takes the big stuff and leaves the little; fire burns the little stuff and leaves the big. After a crown fire—a fire that flashes through a forest canopy—what remains are the tree trunks that logging would have hauled off. Removing them earlier would have lathered the land with post-cut debris called slash—exactly the kind of volatile fuel that fire favors. ...