There’s a better way to tame large forest fires. So why don’t we do it?

There’s broad agreement that wildfires in the American West are getting worse over time. Climate change is one oft-cited culprit, with hotter, drier weather helping fires spread. We’re also building more homes in fire-prone areas, making blazes much costlier. The US Forest Service is now breaking its budget on fire protection.

But there’s another reason for the rise in large fires that often gets less attention. Over the last century, we’ve been suppressing the vast majority of wildfires and letting forests build up thickly with plant growth. So, when a large fire does escape our control, it has more fuel to burn — and can become far, far more destructive:

As it happens, there are plenty of good ideas about how to alleviate this problem. We could reduce the available fuel in forests, either through selective logging or by allowing smaller controlled fires to burn periodically, clearing out brush. That wouldn’t stop all large wildfires, but it would help reduce the number of truly massive infernos that form. It’d also make forests more resilient in the face of drought and fire.

This isn’t some big secret. We usually just... don’t do it. And a fascinating new paper in Science by a team of fire experts asks why we don’t, exploring some of the perverse political incentives standing in the way of a more sensible wildfire policy.

Large wildfires have long been a natural feature of the Western landscape. But, in the distant past, data from tree rings show, these were often low-intensity “surface” fires that cleared out undergrowth and left the bigger trees standing. They helped maintain a healthy ecosystem.

That all changed in the 1900s. As the region’s population grew, forest managers began suppressing smaller fires to protect nearby towns. Today, 98 percent of fires are stopped before they get bigger than 300 acres. But that had perverse consequences. The surrounding forests became denser with undergrowth, which meant that the handful of fires that did break free have much more fuel to burn. The scale of these “megafires,” which can spread all the way up to the canopy and kill off large trees, appears to be unprecedented in the historical record.

One obvious way to prevent these hugely destructive megafires would be to reduce the amount of accumulated fuel in dry forests. In some places, that would involve “mechanical thinning”: going in and selectively logging or clearing out undergrowth. That’s not always as simple as it sounds, since in some forests there are legal constraints around this, in other there are practical hurdles, and in some places it’s just plain expensive. Still, it’s a key part of fire prevention.

Another option would be to allow smaller managed fires that clear out brush. One 2012 study, by Scott Stephens of UC-Berkeley, suggested that intentionally setting “prescribed fires” in forests was a viable method of clearing out the surface brush and preventing even more catastrophic, canopy-killing fires from breaking out. Fighting fire with fire.

The thing is, most forest managers are aware of all this. But putting this policy into practice is much harder than it sounds.

So, in this newest Science paper, a team of researchers led by Malcolm North of University of California, Davis, tried to figure out why the US Forest Service and other agencies still favor suppressing the vast majority of wildfires over other prevention methods.

One problem is that perverse budget incentives at play. The US Forest Service, for example, gets dedicated annual appropriations from Congress to suppress wildfires, and this budget gets supplemented by emergency funding. But programs to thin out forests or set smaller prescribed fires are part of a more limited prevention fund — and this money often gets diverted during severe wildfires to pay for firefighting.

That creates a vicious cycle. Forest managers have limited resources for fire prevention, which in turn allows massive wildfires to rage. And then, in order to fight those massive raging wildfires, they end up raiding their prevention funds.

Meanwhile, allowing smaller managed fires to burn isn’t as simple as it sounds. These fires can somtimes spiral out of control — here are some examples in Colorado and New Mexico — and when they do, people get pissed. So forest managers are understandably worried about liability and casualty risks. It often seems much safer to just suppress most fires, even if it’s more dangerous in the long run.

Another factor: EPA regulations around smoke and air pollution sometimes make it impossible for forest managers to conduct prescribed burns (even though, again, this can worsen the long-run smoke problem by fueling large megafires).

North and his co-authors point out that the current dynamic is unsustainable — especially if global warming will continue to dry out the American West, making wildfires even larger and more frequent in the years ahead.

By way of reform, they recommend that forest managers create new zoning plans for national forests, the way Parks Canada does. Forests near populated areas would be managed through a mix of mechanical thinning and fire suppression. More remote forest areas could be thinned via prescribed fires or by letting smaller natural fires burn themselves out, so long as weather conditions are right.

That would require dedicated crews that work on reducing fuel build-up in forests — crews that don’t get diverted into suppression during wildfire season, as currently happens. (Note that there’s some move toward this already: the authors have high hopes for the US government’s National Cohesive Wildland Fire Management Strategy, drawn up in 2014.)

Crucially, the US government would also need to stop encouraging people to build homes in fire-prone zones. Right now, state and local governments have every incentive to develop these areas — knowing that the feds will pick up the tab for fire suppression.

Reformers have suggested that Congress could limit the mortgage-interest deduction for homes built in particularly vulnerable regions. A federal fire insurance program could help enforce tighter standards and building codes, the way we do for floods. (Studies have found that clearing brush and pruning trees in the 200-foot “ignition zone” around homes can be particularly effective at saving structures from fire.)

Ultimately, North and his co-authors argue, things won’t change dramatically until the public reorients its attitude toward fire and pushes for change: “The core problem has been the lack of a public constituency that advocates for reform of fire-use practices,” they note.

For an example of what a different approach might look like, they point to Western Australia, where forest managers now use mechanical thinning to create “safe-zone anchors” that make it safer to allow smaller wildfires to burn. About 6 to 8 percent of the forest is allowed to burn itself out each year, so as to limit the number of truly massive megafires that form. But that took years of public education to get people comfortable with the idea of fighting fire with fire.

-- Here’s a more detailed look at why Western wildfires keep getting worse.