For millennia the presence of humans on planet Earth hardly made a dent in its ecosystems. Humans were at the mercy of their environment as much as any other creature. But with the advent of agriculture, humans began to influence the planet in major ways. Some scientists posit that the clearing of large swaths of land for planting over the past 10,000 years released enough carbon into the atmosphere to delay the next ice age.
Of course, in the past two centuries the pace of those carbon releases has grown exponentially with the industrial revolution through the burning of fossil fuels. These emissions now threaten to flip the planet into a warm state far beyond anything experienced by humans in their relatively brief time on Earth. The question we must now face is whether humans still live in "the environment" or whether they now are "the environment" by virtue of their actions.
The distinction mattered little as long as we didn’t live in what economist Herman Daly calls "a full world." The introduction to his piece "Economics in a Full World" which appeared in Scientific American in 2005 states: "The global economy is now so large that society can no longer safely pretend it operates within a limitless ecosystem."
And, pretending is all we’ve been doing since the dawn of humans. As it turns out, the biosphere that is our home has been shaped by the very organisms that inhabit it. For example, about 2.4 billion years ago, cyanobacteria which are capable of photosynthesis appeared and began absorbing carbon dioxide from Earth’s atmosphere and releasing oxygen in great quantities back into it. The period has been dubbed The Great Oxidation Event, and it wiped out most anaerobic bacteria (because, of course, they can’t survive in an oxygen environment). As a result, The Great Oxidation Event is regarded as one of the largest extinction events of all time.
We see the imprint of living organisms shaping the biosphere everywhere. The carbon cycle–the very basis of life as we know it–involves plants and microorganisms both on land and in the sea. Even our human bodies are part of it as we breathe in oxygen and expel carbon dioxide. Shell-making aquatic organisms use carbon and calcium from seawater to make their shells. When these organisms die, their shells sink to the ocean floor where they become part of the vast carbonate-rich deposits of sedimentary rocks.
And there is the nitrogen cycle, a cycle critical to the survival of all living things. None of us can live without the nitrogen needed to build the proteins and the nucleic acids (DNA and RNA) we depend on for our functioning. Nitrogen in the atmosphere, however, cannot be utilized by plants. But, it turns out that soil bacteria convert this nitrogen into a form that is usable for plants and therefore usable for the animals that eat those plants. (Lightening also performs this transformation.)
So the principle is that organisms are both acted upon by their environment and act on their environment. They both adapt to their circumstances and attempt to alter those circumstances to enable them to survive and thrive. There can be no doubt that humans do this. Of course, this doesn’t guarantee that all organisms will survive, at least not in their current form. And, that’s how we get evolution on Earth. Organisms gradually change over time or go extinct if they cannot adapt quickly enough to changing circumstances or alter those circumstances enough to allow their survival.
All organisms are continuously acting both to adjust to surrounding circumstances and to shape those circumstances. This is a key insight. We earthbound organisms are not, as Darwin implies, mere helpless actors. Each of us has a role to play in maintaining the web of life. This conclusion is logical. How can we say that wolves are influencing the evolutionary development of sheep without saying sheep are influencing the evolutionary development of wolves?
What can we now say about "the environment" when the dominant force shaping it us? We have interfered in the carbon cycle in a profound way, vastly speeding up the introduction of carbon into the atmosphere and the oceans (ocean acidification). What can we now say about the nitrogen cycle after 1905 when Fritz Haber figured out how to convert nitrogen from the air into a form usable for plants–a discovery that led to modern-day nitrogen fertilizers that have greatly expanded the food supply and thus allowed human populations to skyrocket?
But, runoff laced with these same fertilizers is responsible for the eutrophication of bodies of water. And, it turns out that the long-term use of artificial nitrogen fertilizers actually reduces the productivity of the soil. One affectless but nevertheless ominous observation from recent research on the subject summarizes the problem: Long-term nitrogen fertilizer use "has been implicated in widespread reports of yield stagnation or even decline for grain production in Asia." (For a fuller summary, see this piece in Grist.)
To every action there is a reaction. It just may not show up right away.
In a recent opinion piece in The New York Times Erle Ellis, a biologist, embraced the idea that there is no "environment" that constrains human action. Here is the heart of his argument:
The science of human sustenance is inherently a social science. Neither physics nor chemistry nor even biology is adequate to understand how it has been possible for one species to reshape both its own future and the destiny of an entire planet. This is the science of the Anthropocene. The idea that humans must live within the natural environmental limits of our planet denies the realities of our entire history, and most likely the future. Humans are niche creators. We transform ecosystems to sustain ourselves. This is what we do and have always done. Our planet’s human-carrying capacity emerges from the capabilities of our social systems and our technologies more than from any environmental limits.
Ellis is one of the few scientists I’ve read who understands that what we humans are doing to the Earth is really a political issue–notice that he invokes social science. And, he has given his advocacy services over to the side that proclaims that perpetual growth in the human domain is possible. To repeat: His conclusion stems not from mere natural science, but from social science, that is, the realm of the political.
But, he makes two obvious errors in his piece when he proclaims: "There really is no such thing as a human carrying capacity. We are nothing at all like bacteria in a petri dish."
He is referring, of course, to the classic illustration of the petri dish which ultimately runs out of food for the hungry, multiplying bacteria it contains, and that leads to a population crash among the bacteria. His error is in assigning agency only to humans, in assigning the ability to shape our environment only to humans. And yet, as a biologist who must know the history of planet Earth, he is being disingenuous. Remember the humble cyanobacteria and the huge destruction it wreaked on other forms of life. Ellis says in the previous excerpt: "Humans are niche creators." But, so are all other organisms on the planet, a rather glaring omission. This is, in fact, a key similarity between us and bacteria.
What Ellis imagines is that humans will always and everywhere be successful at creating new niches for themselves–that all the other organisms on the planet will somehow accommodate us enough to allow the human species to grow continuously and its extractions from the rest of the natural world to grow with it. He is right that humans have always altered the biosphere (as has every other organism). But he seems not to understand the current scale of alterations and the rapidity with which they are taking place. Scale matters. Remember Herman Daly’s admonish that we live in a full world. And, that world is on course to change its climate dramatically in just a few decades. Such a time line is unprecedented in human history.
Ellis again has a scientific lapse by simply dismissing the competition and cooperation from other species as inconsequential–for example, competition for basic resources such as food and water and cooperation from such species as bees which pollinate the lion’s share of the world crops. He is too dismissive of human-induced changes in the oceans, the soils and the atmosphere as something humans will always and everywhere be able to survive.
He tells us that 200,000 years ago humans started to transform the planet. What he fails to mention is that it has not been a one-way trajectory skyward. About 70,000 years ago, probably because of climate change, human numbers were likely reduced to just 2,000. The lack of genetic diversity in humans has long pointed to such an event. All of us today come from those 2,000.
But, of course, we’re better equipped than those humans. And today, with our unparalleled knowledge, we wouldn’t foolishly undermine the systems in our biosphere that are critical to our well-being, would we?
Ellis writes with the vast overconfidence of someone who thinks he knows the future with certainty and that humans will always figure something out no matter the scope or rapidity of the changes they face. In his opinion piece he gushes: "Who knows what will be possible with the technologies of the future?" Actually, nobody knows.
But, we humans are not "in charge" of the biosphere. We are only competing and cooperating with various parts of it in a struggle to survive and thrive. Isn’t it obvious by now that the biosphere does not always do what we want it to do and only what we want it to do? It’s as if the law of unintended consequences has never occurred to Ellis.
Given that we know now that all organisms try to remake the biosphere to their liking, this should make us far less confident that we can make everything turn out just fine for humans. Keep in mind that we face a bewildering and essentially incalculable array of actors with whom we are forced sometimes to fight and sometimes to cooperate. In fact, we cannot even know what all of them are and probably are only familiar with a small sliver of all that lives. Our knowledge of the biosphere and the Earth is not just imperfect, it is wildly imperfect. If we’re so smart, why didn’t we avoid changing the climate, devastating the fisheries, degrading the soil through rapid erosion, and lacing the air, water and soil with toxic chemicals in the first place?
Even though Ellis is right that there is no fixed human carrying capacity–because humans, their social and technological circumstances, and the world of other organisms and Earth processes are changing all the time–this is but a red herring. No bona fide scientist has said otherwise. When most scientists refer to human carrying capacity, they mean long-term carrying capacity; they mean thousands of years. And, Ellis never even contemplates the possibility that this fluctuating human carrying capacity might go down! The human story forever goes upward (except, for example, 70,000 years ago, when, due to climate change, it didn’t).
So we have a semantic sleight-of-hand that ducks the long-term problem and places Ellis (whether he knows it or not) firmly on the side of interests that only think short-term, primarily the industrial and commercial interests. We are back to politics, again. With which interests should we ally ourselves? The well-being and futurity of the human race or the short-term interests of powerful elites?
William Catton Jr., author of the ecological classic Overshoot, prefigured the coming of the Anthropocene, an age of the Earth dominated by human actions–where menacing geological changes such as changes in the chemistry of the ocean and the atmosphere take place by dint of human action and within a human lifetime. Catton gave humans a new name, homo colossus, a human-tool hybrid with immense power to shape the globe. With worldwide geologic changes coming this fast, what will it mean from now on to refer to the geologic time scale?
If we are indeed already in the Anthropocene, then "the environment" cannot be "out there." And, it cannot be "preserved." The environment is us and everything else together constantly in flux. It is no longer a static scientific construction, but a political one within which we humans are firmly situated along with all the other organisms and Earth processes. We cannot be above or apart from it. We cannot "save it" as actors from beyond.
But, we can decide which values we want to defend. With apologies to some of my geologist friends who understand rightly that the human project on planet Earth will just be a blip in Earth’s history–please stop identifying with the rocks! Rocks are an excellent area of study; and, we have geologists to thank for much of what we know about Earth’s systems. But, the time has now come to realize that that knowledge has political implications for what we as humans will actually do from here on out.
The advent of the Anthropocene has wiped out the distinction between human history and natural history. And so, my minor temper tantrum over geology applies to all the other natural sciences. There is no distinction between us and the natural world. There is just the thin membrane of life and life processes clinging to the Earth’s surface which we call the biosphere and of which humans are merely a part.
It has always been thus. But now, it is imperative that we understand this if we wish to salvage anything we call human in the century to come.
P.S. The inspiration for this piece comes from Bruno Latour who gave the Gifford Lectures last year, particularly the third and fourth lectures. And, I thank my friend Jim Armstrong for some thoroughly stimulating discussions about these lectures and Latour’s latest work.