Outside/In: Why Pine Barrens Need Fire To Survive
Devastating wildfire seasons have become the normal on the West Coast of the United States - a result of drought (exacerbated by climate change) and poor management practices. But one way to fight out of control burning, is with under control burning. In today’s edition of 10X10, an up close look at a wooded ecosystem that doesn’t just benefit from fire, but actually needs it to survive.
And you’ve maybe heard that we’re in the midst of a mass extinction. But not every species suffers equally. On the second half of the show, a tale of two birds: one, a rare specialist that’s struggling to survive … and the other, a grosser species that’s adapting just fine.
10X10: Pine Barrens
Sam Evans-Brown & Taylor Quimby
This segment is focused on 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 gets started in one of these areas, it spreads quickly through the understory. Historically, fires would sweep through pine barrens every 50 years or so, and 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 that started with a paper published 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 that start a lot of fires in the United States, but researchers frequently find that places that indigenous people used to live often coincides 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.
Vultures Inherit The Earth
The Bicknell's Thrush is a bird that can only live in a few very, very restricted places. It spends its summers in dense alpine forests in the Northeast of the US. In the winter, perhaps as many as 90 percent of the birds fly to the Dominican Republic. It's a bird without many options, and that makes it a poster child for what's to come.
“They’ve pigeon-holed themselves into a pretty narrow ecological niche,” said Chris Rimmer, executive director of the Vermont Center for Ecostudies, a little research and conservation outfit that has taken up the challenge of trying to study and conserve the thrush.
In other words, the Bicknell’s thrush is a specialist: on both ends of its range, it lives only in a very narrow band of habitats. They don’t seem to know how to live anywhere else. “If these habitats [thick stands of stunted conifers on steep mountain slopes or near tree-line] disappear from our mountain tops,” explained Rimmer, “I don’t think the birds are going to just find a different place to go.”
Consider now, another bird: the turkey vulture.
“I think turkey vultures are just about a perfect creature,” said Katie Fallon, author of Vulture: The Private Life of an Unloved Bird. “They breed from south central Canada, throughout most of North America, Central America, and all of South America. They’re even on islands... Caribbean Islands... the Falkland Islands. They’re a bird that can be seen by almost everyone in the hemisphere.”
Turkey vultures aren’t picky. They will nest in dark crevices, abandoned buildings, the nests of other birds, mammal burrows, and even quiet spots on the forest floor, if nothing else is available. They are also shockingly efficient. When soaring, their heart-rate is nearly the same as when they are sleeping, which has even led some to suggest that turkey vultures might actually take quick naps while flying. This is just one of the many delightful facts about these birds—my personal favorite is that their stomachs are acidic enough that it can neutralize cholera, botulism and anthrax.
When you add these various evolutionary talents up, you get an animal that is poised for success in virtually any habitat; basically, you have a generalist on your hands.
The world is made up of many species, and any one of them will loosely either fit the profile of a generalist or a specialist. That has always been true. What is newly true is that species are disappearing at an alarming rate, and many scientists believe we’re seeing the beginnings of something that will eventually be recognized as a mass extinction event.
And the problem is that these extinctions are not distributed equally. They’re coming for the specialists first.