Wilderness as the arena for evolution

In November 1989—less than a year into George H.W. Bush’s first term—a now-defunct “community-based educational project” in New York City called The Learning Alliance hosted a debate between two obscure but influential voices in what was then known as the “ecology” movement. On one end of the stage was Murray Bookchin, a 68 year old anarchist, eco-socialist, and prolific author from Vermont, best known today for having butted heads with Bernie Sanders in the heady days of 1980s Burlington politics and for having inspired the radical Kurdish People's Protection Units (YPG) in Rojava. On the other end was Dave Foreman of Albuquerque, New Mexico, best known for co-founding Earth First!, his subsequent arrest by the FBI on charges of conspiracy, and later co-founding The Wildlands Network.

The occasion for the debate was a few years of rising tensions between branches of an ascendant but marginal radical environmentalism: Bookchin was present as a representative of a race-and-class-conscious social ecology faction; Foreman as a representative of the biocentric (critics would say misanthrophic) “deep ecologists”. Their discussion was recorded, transcribed, and eventually published under the title Defending the Earth: A Dialogue Between Murray Bookchin & Dave Foreman.

I first heard of the book a few weeks ago over Twitter (thanks, Jamie!), found a copy online, and made my way through the slight paperback over the course of a few mornings. Despite its brevity and unusual format, it is what you might call a Rich Text: from conflicting theories of political change to heated exchanges on race and immigration, Bookchin and Foreman’s disagreements remain shockingly relevant today, with only a few moments where their discussion betrays its origins as an artifact of an earlier era. (The idea that cities are more resource-intensive than dispersed rural settlements, for instance, is an interesting window into a time where moral panic over urban decline was rampant and back-to-the-land movements had recently reshaped the country’s political geography.)

Today, though, I want to focus on a point of common ground between Bookchin and Foreman. It’s an argument I’ve heard made frequently over the years by conservationists as part of the rationale for affording more land the highest possible form of legal protection: the idea that wilderness areas set the stage for evolution to go on its merry way. “Natural evolution cannot be denied its own spontaneity and fecundity. That is why one part of our struggle should always be to protect and expand wilderness areas” states Bookchin early on (p. 35). “Wilderness areas are the arena for natural evolution” (p. 72), agrees Foreman later, echoing his writings elsewhere. What do they mean by this? Why do they believe it? Are they right?

First, some definitions. Wilderness is a social construct, impossible to precisely demarcate, and, I argue, not actually that complicated. For the purposes of discussion, it means big chunks of mostly unmanaged land, with limited direct or indirect human modification of habitat (at least recently). There are many gray areas, but for now we’ll stick to the geographic and cultural context Bookchin and Foreman are most familiar with and are clearly referring to—post-colonial North America—where we have a legal means for identifying it.

Defining “natural evolution” as either Bookchin or Foreman intended to use the term is trickier. Extinction, for example, is an evolutionary process, but maintaining the potential for extinction is not the first thing that comes to mind when you think of arguments for preserving wilderness—not in the least because extinction clearly gets on fine (thrives, even!) in the absence of large landscape conservation. It’s clear they’re referring to something more specific.

Biologists commonly define evolution as the change in copies of an allele (a variant of a particular gene) in a given population over time. This definition is not without its problems, but its simplicity makes it a powerful epistemological and pedagogical tool. Yet I doubt Bookchin, Foreman, or others who evoke the evolutionary potential of wilderness are being so precise: again, allele frequencies hardly require wilderness to change, and in many contexts, may change faster in its absence, e.g. in fragmented landscapes with small populations more prone to random changes in their composition.

Instead, I suspect that Bookchin and Foreman are referring to aspects of evolution that are more tangible and less abstracted. My hunch is that when most non-scientists think about evolution, they are likely to first think of one of two processes: either changes in an organism’s traits over time (something that falls under the umbrella of the term anagenesis), or the formation of new species that can coexist in space and / or time (cladogenesis). Anagenesis and cladogenesis certainly seem like better fits for Bookchin and Foreman’s argument. But do these processes actually need wilderness?

First, let’s consider anagenesis. To simplify things a bit, we can think about the rate at which traits evolve in a group of interbreeding organisms as determined by (1) the amount of genetic variation that exists in a population already; (2) the amount of genetic variation that enters the population through mutation; (3) the amount of genetic variation entering through immigration; and (4) the strength of natural selection to match traits to a particular environment.

The amount of existing genetic variation in a population (1) is itself controlled by historical contingency and a suite of evolutionary mechanisms that we will ignore for now. All else being equal, there is a weak, complicated, but generally positive relationship between the number of individuals in a population and the how much genetic variation that population contains. (You find an interesting recent paper on this topic by Vince Buffalo and colleagues here). Because wilderness areas can generally support larger populations, I think it’s fair to say that they should often—but not always—support more genetic variation than non-wilderness habitats, at least in the absence of other information about landscape change and evolutionary history.

In contrast, I don’t think there’s any reason to expect the amount of genetic variation that enters a population through mutation (2) to meaningfully differ between wilderness and non-wilderness habitats, barring some fascinating case-specific biology coming to light. Mutation rate should be wilderness-agnostic.

The amount of genetic variation brought in by new immigrants (3) is a little more complicated. If we assume immigrants randomly select their new home in way that approximates throwing a dart at a dartboard while blindfolded, the greater size of wilderness areas should mean that they receive more arrivals by chance compared to non-wilderness habitat, controlling for the proximity and size of the “sources” of these immigrants. If we assume immigrants are actively choosing habitat in their new homes based on its perceived quality, we’d have another reason to expect more immigration into wilderness. So immigration should be wilderness-positive, I think.

Lastly, natural selection (4). Without specifying a particular type of selection, I have no expectation here. I’ll cautiously say selection is also wilderness-agnostic. Considering all four mechanisms together, though, it seems reasonable to predict that we should see faster rates of trait evolution in wilderness areas, because of their potential to hold more genetic variation, and the increased input of genetic variation from immigrants.

(Legally-designated wilderness in western Colorado to provide some visual interest in the middle of a lengthy newsletter.)

Second, let’s consider cladogenesis. In animals, new species most commonly form when populations become geographically isolated from one another, can no longer interbreed regularly, and are independently subjected to the factors discussed above. Wilderness areas, large by our stated definition, should provide more opportunities for geographic isolation than a small patch of non-wilderness habitat—but not necessarily multiple small patches of non-wilderness habitat, assuming they are all occupied. In fact, you can imagine that an archipelago of non-wilderness habitat patches would be very efficient at generating new species through enforced isolation, assuming they were large enough to maintain distinct populations for a million or so generations.

Alternatively, new species can form if natural selection for opposing traits reduces the amount of interbreeding between populations. Some types of natural selection—such as selection for different tolerances for drought—are probably better maintained in large chunks of habitat that span climate gradients, and are therefore likely to be stronger in wilderness areas. Overall, though, I’m uncomfortable taking a strong stand on whether wilderness is more conducive to types of speciation that are driven by natural selection, and so I’ll conclude that cladogenesis is wilderness-agnostic, at least on balance. (Feel free to argue with me on this one.)

So to sum it all up: wilderness is intuitively important for maintaining the genetic variation that is the raw material for flashy evolutionary processes, but more because it can support healthy populations than any particular evolution-enhancing special sauce. You can imagine “sterile”, non-wilderness landscapes managed to maintain the same processes. And of course, there’s a large scientific literature dedicated to the best ways to do exactly that.

At the risk of undermining my own argument, though, I think this deconstruction misses something important. To reiterate Bookchin: “Natural evolution cannot be denied its own spontaneity” (emphasis mine). Elsewhere in Defending the Earth, Foreman warns against the limits of rationalism: “Rationality is a fine and useful tool, but it is just that, a tool, one way of analyzing matters. Equally important is intuitive, instinctive awareness. We can become more cognizant of ultimate truths sitting quietly in the wild than by sitting in libraries reading books” (p. 53).

I highlight these quotes to emphasize that while Bookchin and especially Foreman (who had a long association with the conservation biologist Michael Soulé, who thought about these issues very clearly and before most other people) talk about wilderness being the arena for evolution, they aren’t scientifically wrong, necessarily. But they are also getting at a sort of biological randomness which is not endemic to wilderness areas but takes on a different aesthetic valence there—a context-dependent perception of the relative degree of self-determination of nonhuman life. In wilderness, whatever that means, we perceive evolution to proceed in a more unconstrained, unfettered way.

That, of course, says more about us than it does about either wilderness or evolution. I don’t think this is surprising: our modern conception of wilderness remains much more tightly tied to the transcendentalism of Thoreau, Emerson, and Muir than to Darwin or G. Evelyn Hutchinson, even as it has become a unit of scientific analysis. It’s a fascinating example of how science both shapes and is shaped by broader cultural currents—in this case, what the environmental philosopher J. Baird Callicot might call “That Good Old-Time Wilderness Religion.”