“A drab, unassuming mollusk the size of a thumbnail, the Asian clam, has transformed San Francisco Bay. In vast portions of the estuary’s intertidal zone, it has displaced virtually all other invertebrates, reducing biological diversity to almost zero.”
That Asian clam sounds like a real nuisance.
From an ecological perspective though, the clam should be proud of itself. It has adapted to its environment better than the competition, vanquishing them in the process. As invasive species go, it’s a real success story, and one with a familiar ring: reducing biological diversity to almost zero.
Humans are, of course, driving the mass extinctions of other species. Unfortunately, our extreme level of dominance is boomeranging and threatening our own existence. Climate change results directly from our unfettered ability to overdraw and exploit certain resources from our environment. And its looming threat is raising a chorus in favor of shifting to a more sustainable impact on the planet.
Is it even possible, in principle, for a species to design its ecological role?
The desire for sustainability raises an important question: Is it even possible, in principle, for a species to design its ecological role? Normally, we would look to science for an answer. In this case, however, we treat sustainability as a moral or political issue. We seem to assume that our collective human agency (the will and ability to act) is all that is needed to deal with the problem. This creates a disconnect, as agency is obviously not at the heart of what defines a species’ ecological nature. When we talk about our impact on the biosphere, we are dealing first and foremost with a biological phenomenon. Ideally we would search through a solution making use of evolutionary biology and ecology. More specifically, we can narrow it down to the sub-discipline of community ecology. This is the branch of science that examines various aspects of species structure and interactions within ecosystems: competition, mutualism, species richness and their ecological niches.
Human society and the biosphere are also complex systems. Beyond ecology, complexity theory can help us understand some of the inherent limitations to their deliberate design. We know that climate change is caused by greenhouse gases produced by the burning of fossil fuels. Now, if your house is too warm, all you have to do is turn down the thermostat. It is tempting to believe that we can also stop global warming by using a similar method: We simply convince, or direct, everyone to turn down the heat. This is an example of the reductionist fallacy. The problem with this kind of thinking is that human society is more than the sum of its parts. It is a complex system with properties such as emergence, nonlinearity, and self-organized criticality. As a complex system, the biosphere self-organizes from the bottom up. Its behavior cannot be easily engineered from the top down. Attempting to do so often leads to unintended consequences. For example, Australia imported cane toads to help with pest control. Instead of eating the pest beetles, they decided to eat pretty much anything else they could swallow. The cane toad turned out to be one of the most disastrous invasive species in memory.
So let’s turn now to applying both community ecology and complexity theory to examine the root of our competitive dominance, and what we can do about it.
It happens that biodiversity tends to increase in ecosystems untouched by humans. Life, as a general rule, tends to greater and greater complexity. Part of the reason is that there are natural, or rather systemic, limits on a species’ ability to outcompete others. To gain a better understanding of these limits, community ecologists turn to a thought experiment: What dynamics would need to be in place in order for a species to fully dominate?
The first such thought experiment was carried out by an ecologist named Richard Law in a 1979 paper that studied the effects of predation on the age at which the prey reproduce. Law observed that there are always constraints on reproduction, including predation and the time consumed in generating offspring (Law, 1979). He called a hypothetical organism that could escape these constraints a “Darwinian demon.” This demon can reproduce without incurring any costs, and it can maximize all aspects of fitness simultaneously.
A different kind of Darwinian demon emerged in 2001 with the publication of a paper by Olof Leimar. This one is different from real-life organisms in that it can create nonrandom, fitness-enhancing mutations (Leimar, 2001). Normally, mutations are not only random, but also most of them are fitness-reducing. Due to the random nature of mutations, an organism may never make it from a local to a global fitness peak. But this Darwinian demon knows where in the fitness landscape the global fitness peaks are located and creates exactly those mutations needed to get there.
A third type of demon is also relevant to our own ecological behavior. This demon is named after Evelyn Hutchinson, a pioneer in the field of community ecology. It was introduced by Kneitel & Chase in a 2004 paper on trade-offs in community ecology. Trade-offs are one of the main reasons why ecosystems maintain high levels of biodiversity (Kneitel, Chase, 2004). For example, consider defenses against predators. Turtles are heavily armored. The trade-off is they are slow and easily caught. A determined predator can therefore overcome the armor and keep turtle numbers down. Similarly, lizards are quick but easy to eat when caught. Again, a predator can adapt to exploit that trade-off. This brings us to the Hutchinsonian demon: It would be heavily armored and quick. No trade-off is necessary, allowing the demon to dominate its ecosystem.
One might think that invasives like the Asian clam would qualify as Hutchinsonian demons. The fact is that these types of species are rarely intrinsically dominant. Instead, they acquire their invasiveness through human actions. We remove them from the co-evolutionary network they evolved in, where they faced the same kinds of trade-offs that other species in their native community did, and put them in a new ecosystem where they face fewer trade-offs. This gives them an unfair advantage (such as a lack of predators and parasites) over species in their new community. Moreover, invasives still face some trade-offs, which limits their ability to spread to new habitats or geographical areas. You won’t find Asian clams dominating any terrestrial habitat, and kudzu only ate the south, not the north.
Could there really be an animal that is better armored than a turtle and quicker than a lizard?
Considering the ubiquity of trade-offs in real life, it may be hard to imagine that a true Hutchinsonian demon is possible. Could there really be an animal that is better armored than a turtle and quicker than a lizard? To encounter one, we have only to get in our cars. Not only can we get away from any predator chasing after us while driving, if we did stop, we’d still be safe inside the car. This lack of tradeoffs applies to any habitat, even those we normally don’t inhabit, like the ocean. It doesn’t take a very powerful boat to get away from the most formidable oceanic predator: a pod of orcas. And even if they did catch up, we would still be safe and could enjoy watching them. Indeed, humans qualify as global Hutchinsonian demons.
The above ‘fast armor’ example illustrates how our lack of trade-offs affects our ecological behavior: We occupy more than one niche, and our niches evolve culturally. Normally, species find their niches through co-evolutionary adaptations which are gene-based, and every species occupies only one niche. Our niche evolution occurs independent of other species. It is the result of cultural co-evolutionary interactions among us. Our cultural adaptation is sped up (10,000 times as fast as genetic adaptation and still accelerating) and highly directed. We can come up with radically new concepts without having to implement inferior intermediate versions. We can go straight from one adaptive peak (legs) to an even higher one (wheels) while avoiding the valley of mal adaptation. In other words, in addition to being Hutchinsonian demons, we are also a cultural version of Leimar’s demon.
As we become aware of the cost of our increasing dominance, can’t we just culturally adapt and reduce it? From an ecological standpoint, this is a tall order. Usually every species reproduces until it reaches the carrying capacity of its environment. Further, our collective self-interest is an emergent phenomenon. Most of us, unfortunately, don’t roll out the door every morning wondering what we can do for society. Instead, cooperation at a global scale rises from our local interactions (i.e., respecting our neighbor’s property rights). Overriding those local interactions requires either coercion accompanied by an intrusive monitoring regime (inherently unpopular) or a mass shift in cultural attitudes which can only be achieved through self-organization across wide geographic scales (inherently difficult).
In a sense, we may have reached the limits of our status as a Hutchinsonian/Leimarian demon. First, with climate change we are stuck in a Hutchinsonian trade-off between our collective and our individual self-interest. It is not that a predator is exploiting this trade-off, but that the trade-off itself is limiting our ability to reach the global fitness peak (of arresting climate change). Under this concept, the only way to relax that trade-off is for technology to deliver a solution that is both in our personal and our collective self-interest to implement. Second, even at its blinding speeds, there is no particular reason why our cultural evolution (i.e., that technology) must outpace the rate at which we approach a climate tipping point. The fact that we have been a great Leimerian demon for the past 10,000 years or so doesn’t guarantee us much unfortunately.
Given what we know about ecological dynamics, what can humans actually do about the situation? Perhaps the first step is to recognize our role as Darwinian demons. There is something very technical about the concept of course. This makes it hardly a subject that can trend on Twitter. On the other hand, a demon is a good analogy, one we can easily grasp. If we focused on the ecological and not the value-laden political argument, it is possible we could make more progress toward changing both cultural attitudes and our technological pace (given the possibility of increased investment in clean tech). There is no silver bullet here, but awareness and acceptance of our ecological nature could be the first two steps toward change.
Law, R. Optimal Life Histories under age-specific Predation. American Naturalist 114: 399-417 (1979).
Leimar, O. Evolutionary Change and Darwinian Demons. Selection2 (1-2):65–72 (2001).
Kneitel, J.M. & Chase, J.M. Trade-offs in community ecology: linking spatial scales and species coexistence. Ecology Letters, 7, 69–80 (2004).
Silvertown, J. Demons in Eden. The paradox of plant diversity. Chicago and London: Chicago University Press (2005).
Rolf Muertter is an Anthropocene ecologist, studying the evolutionary and ecological implications of human dominance.