Another year… another record-breaking wildfire season. Thanks to climate change the fire season now starts sooner and ends later. Scientists also say climate change will make lightning more frequent, and winds more powerful… basically the world is a tinderbox. But what if I told you that maybe the problem with all these big, out of control fires was *not enough* fire.
This episode begins with an introduction to an ecosystem that needs fire in order to flourish: the Pine Barren. Pine barrens occur on well-drained soils, and tend to be tinder dry. This means that when a fire got started in one of these it would spread quickly through the under-story. These fires would sweep through every 50 years or less, and so the plants that thrived here are ones that are well adapted to the flames.
There's a long-standing debate in the world of fire ecologists and evolutionary plant biologists, which started with a paper in 1970. The so-called "Mutch Hypothesis" was that "fire-dependent plant communities burn more readily than non-fire-dependent communities because natural selection has favored development of characteristics that make them more flammable." In other words, the evolutionary strategy of plants in forests like this isn't just to survive fires, but to propagate them, by developing waxy, oily leaves and structures that made them extra-flammable.
Subsequent researchers have refined this hypothesis—perhaps this strategy works best because it "kills thy neighbor," or perhaps it's because hot, quick fires do less damage to the plant's roots—while others have rejected it. It's a difficult hypothesis to prove, but if one could do it, it's an example of plants doing something a lot of us think is just the domain of vertebrates: engineering their environment to be more welcoming for species that thrive after a fire.
There's an interesting question that pops up when you examine the archaeological record of environments like these pine barrens. Why are they here? There are plenty of lightning strikes to start a lot of fires in the United States, but researchers frequently find that places that indigenous people used to live often coincided with fire-dependent species. The Confederated Salish and Kootenai Tribes of Western Montana have documented a rich history of intentional burning, and researchers studying fire regimes in the West have found that indigenous practices doubled the amount of fires that would naturally be observed.
But in the early 1900s Americans began aggressively staunching every fire that started in wildlands in order to stop damage to property and loss of life. While this worked for many decades, it led to an accumulation of "fuel" in Western ecosystems that were evolved to burn, so when fires eventually did break out they were even more powerful than they would have been. In the East, it is causing the slow demise of these fire-dependent ecosystems — along with the species that depend on them — as tree species that cultivate damp shady forests move in.
We’ve used fire to dramatically reshape our environment for as long as we’ve known how to make it, and the last 100 years or so of aggressively putting out every fire that starts has been this odd departure from that history. Now, we’re paying the price for that strategy in the form of deadly wildfires out West, and disappearing pine barrens in the Northeast. The woods doctors have a prescription in mind though, and all it takes is a couple dozen firefighters and a drip torch, if we can get over our fear of the flames
Outside/In was produced this week by Sam Evans-Brown, and Taylor Quimby, with help from Hannah McCarthy, Justine Paradis, Nick Capodice, and Jimmy Gutierrez. Erika Janik is our Executive Producer. Maureen McMurray is the director of cutting jargon from early podcast drafts.
Thanks this week to Melissa Thomas-Van Gundy and Greg Nowacki of the Forest Service, William Patterson of UMass Amherst and the many folks at the Nature Conservancy who helped us figure this story out.
Music in this episode by Franco Luzzi, Blue Dot Sessions, Jason Leonard and Ikimashoo Aoi.
Our theme Music is by Breakmaster Cylinder.
Outside/In is a production of New Hampshire Public Radio.