What Happens When Apex Predators Take Over the Planet
Stefano Mancuso on the Extinctions of the Anthropocene
Whether Burundian, Italian, or Icelandic, humans are the most accomplished predators. Like a lion observing, sleepy and satisfied, the piece of the savannah that is his territory, with the serene awareness that no other animal can contest his sovereignty over it, the human race considers the entire planet as something under its exclusive jurisdiction. Earth, the home of life, the only place we know of in the universe able to host it, is considered by humans as neither more nor less than a simple resource: to be eaten, to be consumed. Something similar to a gazelle in the eyes of an always-hungry lion.
That this resource might come to an end, putting at risk the very existence of our species, does not seem to interest us. Have you ever seen that science fiction film in which some really wicked alien species, after having consumed the resources of countless other planets, swoops down on the Earth like a swarm of grasshoppers from space intent on turning it into a wasteland? Those aliens are us. Only the other planets still left to be destroyed after Earth do not exist. We would do well to understand this as soon as possible.
The consumption of organic material produced by other living beings is typical of animal life. Not being able, as plants are, to capture the energy of sunlight autonomously, animals must perforce rely on the predation of other living beings to ensure their survival. This is why plants are always pictured at the bottom of those typically pyramidal illustrations that we see everywhere bearing the name of the food pyramid, or the ecological pyramid, or the trophic pyramid. Whatever the name, the concept is always the same. There is a pyramid with plants, the producers, occupying the lowest level, and then proceeding upward through the various trophic levels. First, the herbivores that eat plants, then above them the carnivores that eat meat, and then the omnivores that eat both plants and meat, and so on, until you get to the apex predators, which are at the top of the food chain.
I have always found these representations of plants as the lowest level of a pyramid to be rather ungenerous, not to say wrong. It would seem to me more correct that the top should be reserved to the organisms that produce chemical energy, rather than those that consume it. I mean, in an automobile isn’t the most important part the engine? All the rest is not essential. Well, plants are the engine of life, the essential part; all the rest is just auto body.
Every time that the energy produced by plants is transferred from a lower level to the next higher level of the pyramid (e.g., when the herbivores eat plants) only 10 to 12 percent of the energy is used to constitute new body mass, thus becoming stored energy, while the rest is lost in various metabolic processes. Therefore, at each successive level we will find 10 percent of the energy present at the preceding level. This is a precipitous drop. Just think, if we attribute to the primary producers (plants) an arbitrary energy level of 100,000, the successive levels will be 10,000, 1,000, 100, 10, 1, and so on. In practice, the organisms positioned at the top of the pyramid, the so-called apex predators, are the least sustainable in terms of energy that one can imagine.
Students of ecology have been debating for years whether or not humans, on the basis of their diet, should be considered apex predators. Some claim that the inhabitants of the various nations of the Earth have different trophic levels, varying from the 2.04 of Burundi, which has a diet that is almost exclusively vegetarian, and, therefore very close to the level 2 of pure herbivores, all the way to the 2.57 of Icelanders, who, on the other end of the scale, have a diet that is just 50 percent vegetables. For anyone who is interested, these trophic levels would make us comparable to pigs. Other ecologists, instead, believe that humans should be considered the apex predators of every trophic chain.
I have always found this debate fascinating in its futility. It is obvious that humans are the only true apex predator on the planet. What’s more, humans’ peculiarities make them incredibly more dangerous for other species than any other living being. It is precisely in their activities as apex predators, that is, as the maximum expression of animal life, that humans are consuming non-regenerable resources at an ever-faster pace, and with the waste products of this senseless activity are increasingly polluting air, soil, and water. How dangerous this predatory activity is and how much damage it has already done is hardly even noticed. Sure, there is a lot of talk about global warming, climate change, urban pollution, decreasing biodiversity, and so on, but I do not believe that the gravity of the situation is clear to most people. At least I hope that is the case. If not, it would mean that humanity has lost all sense of its own future.
Many of you will have heard talk about the Anthropocene—I have also written about it recently. The Anthropocene is the name for the geological era we live in, whose dominant feature is the seismic effect of human activity. Humans, for example, through their continuous and uncontrollable need to consume, are so profoundly affecting the characteristics of the planet as to have become the cause of one of the most terrible mass extinctions of all time. In the history of our planet, catastrophes of similar dimensions have happened only after apocalyptic events such as asteroids, volcanic eruptions, inversions of the Earth’s magnetic field, supernovas, the rising or lowering of ocean levels, and glaciations. The frequency of such events has been estimated to range from once in every 30 million to once in every 62 million years, and their causes have been hypothesized as depending on circumstances such as oscillations of the galactic plain or the Earth’s passage between the spiral arms of the Milky Way.
Throughout its history, Earth has suffered five mass extinctions and a certain number of minor extinctions. The five big ones, identified by Sepkoski and Raup in a noted work from 1982, are: 1) the Ordovician-Silurian extinction, from 450 to 440 million years ago, when two events occurred which eliminated between 60 and 70 percent of all species, representing the second biggest of the five major extinctions in terms of the percentage of genera extinguished; 2) the late Devonian extinction, lasting perhaps some twenty million years, during which about 70 percent of extant species disappeared; 3) the extinction during the transition from Permian to Triassic, 252 million years ago, the most dramatic extinction event to strike the Earth, where from 90 to 96 percent of extant species were swept away; 4) the Triassic-Jurassic transition extinction, 201 million years ago, which eliminated from 70 to 75 percent of species, and, finally 5) the extinction during the transition from Cretaceous to Paleogene (the one in which dinosaurs became extinct), 66 million years ago, which killed off 75 percent of living species.
Today we are in the thick of the sixth mass extinction, an event of such proportions that perceiving its consequences is difficult indeed. The current extinction rate of species is unimaginable. In 2014, a research group coordinated by Stuart Pimm of Duke University estimated the Earth’s normal extinction rate, prior to the appearance of humanity, as 0.1 extinct species per million species per year (0.1 E/MSY). The current rate appears to be 1,000 times greater, while models for the near future would indicate an extinction rate as high as 10,000 times normal.
These are the numbers of an apocalypse. Never in the history of our planet, not even during the most catastrophic mass extinctions, has there been such a high rate of extinction and, above all, compressed within such an imperceptible span of time. The past mass extinctions that we know about, as rapid as they were, have always come about over a span of millions of years. Human activity, on the contrary, is concentrating its lethal effect on other living species in a handful of years. The entire history of Homo sapiens began just 300,000 years ago, less than the blink of an eye compared to the 3.8 billion years of life. Those who worry about the invasiveness of such magnificent vegetable species as the ailanthus, the robinia (black locust), the pennisetum (fountain grass) and others, because of their capacity to drive out native species from their home territories, should be aware that, compared to the invasiveness of Homo sapiens, the dangerousness of any other species, animal or vegetable, is nothing more than a joke.
At the end of 2017, 15,364 scientists from 184 countries signed a declaration, “World Scientists’ Warning to Humanity: A Second Notice,” in which they affirmed that “we have unleashed a mass extinction event, the sixth in roughly 540 million years, wherein many current life forms could be annihilated or at least committed to extinction by the end of this century.” We might be tempted to just shrug our shoulders at this news. Many, deep in their hearts, might think, “We have destroyed entire human civilizations, why worry about the disappearance of a number, high as it might be, of animal and vegetable species? We will survive without any problem.”
I think this is actually the biggest danger: thinking that what we are doing does not directly affect the preservation of our civilization, not to mention the survival of our species. How could the extinction of plants, insects, algae, birds, and various mammals have an impact on our survival? OK, it’s sad that rhinos, gorillas, whales, elephants, bananas, monk seals, lightning bugs, and violets are becoming extinct, but, after all, how many of us have ever even seen one? For us city dwellers, nature is the stuff of documentaries, it has nothing to do with us. What interests us is the interest rate spread, the GDP, Euribor, the Nasdaq—these are the things that could cause the collapse of civilization as we know it.
Wrong! I repeat, it is the very idea, so widespread as to have become a cliché—that we humans are outside of nature—that is truly dangerous. The extinction of such a high number of species, in such a short time, along with ongoing and accelerating declines in species’ populations, is something whose consequences we cannot estimate. Rodolfo Dirzo, a professor at Stanford and an expert on species interaction, writes, “Our data indicate that beyond global species extinctions Earth is experiencing a huge episode of population declines and extirpations, which will have negative cascading consequences on ecosystem functioning and services vital to sustaining civilization. We describe this as a ‘biological annihilation’ to highlight the current magnitude of Earth’s ongoing sixth major extinction event.”
Now, it’s true that Cassandras have never been well liked by anybody, and often we even forget that Cassandra—the original—the unheeded prophetess, was right! Being aware of the disaster that our consumption is creating should make us all more careful about our individual behavior, but also angry toward a model of development that in order to reward a few is destroying our common home.
Excerpted from The Nation of Plants by Stefano Mancuso, translated by Gregory Conti. Soon to be published by Other Press.