Overshoot
by Jason GodeskyThirty-two miles of tundra poke out of the Bering Sea, 183 miles WNW from Nunivak Island, at a place we call St. Matthew’s Island. During the Second World War, the United States Coast Guard set up a loran (long range aids to navigation) on the island, to help ship traffic through the Bering Sea. The loran required a staff of 19 men, and in 1944, the Coast Guard arranged for 29 reindeer to be barged over from Nunivak, to serve as an emergency food supply for the men. When the war ended a few months later, the loran was shut down and the staff returned home before shooting a single reindeer. The reindeer found themselves in a marvelous situation: a nearly uninhabited island with no predators whatsoever, and thick beds of lichen for food.
In 1957, a biologist working for U.S. Fish and Wildlife Service named David Klein made his first visit to St. Matthew’s, to study the effects of the reindeer introduction on the island, with field assistant Jim Whisenhant. They counted 1,350 fat reindeer—forty-six times the number originally introduced to the island. Klein also noticed that the reindeer had trampled and overgrazed several of the lichen mats. Arranging transport to the island for follow-up studies became an issue. Klein was not able to return for six years, until the summer of 1963. When he and three other scientists reached the island, they found bent-over willows, and reindeer after reindeer. The herd had reached a size of 6,000—47 for every square mile of the small island. “They were really hammering the lichens,” Klein said.
Klein was not able to return again for a time, but he heard a story from the crew of a Coast Guard cutter that had gone ashore to hunt some reindeer in August 1965, claiming to have found dozens of reindeer skeletons bleached in the cold tundra. The next summer, 1966, Klein returned to find the island filled with reindeer carcasses. They counted only 42 remaining reindeer: 41 females, no fawns, and only one male with abnormal antlers and apparently incapable of reproducing. By the 1980s, with no reproductive members remaining, the St. Matthews herd had completely died out. Klein published his data in “The Introduction, Increase, and Crash of Reindeer of St. Matthew Island” (J. Wildl. Mngm. 32(2):350-367. Klein, D. 1987). The reindeer of St. Matthew’s island have since become the iconic example of the ecological principle of overshoot.
A species may greatly overshoot the long term carrying capacity of its environment. (Its population may become greatly larger than its environment can sustain.) Overshoot becomes possible when a species encounters a rich and previously unexploited stock of resources that promotes its reproduction.
The creation of stocks is due to ongoing geological and biological activity. A resource stock forms when a part of the daily production of a resource, a flow, accumulates slowly without being exploited, perhaps over millions of years. An enormous stock of a resource may accumulate before it encounters a species that can exploit it easily. After such an encounter, only predation and disease limit reproduction of the species.
Without significant predation or disease, and while large amounts of the stock remain easily available, the population of a species can grow to a size hundreds of times that which can be supported by the flows that created the stock. The daily production of a resource is a mere trickle compared to the flood available from a stored accumulation.1
Overshoot is intimately tied up in the ecological concept of carrying capcity, “the population level that can be supported for an organism, given the quantity of food, habitat, water and other life infrastructure present.” In his important book, Overshoot, William Catton explains overshoot in terms of detritus, or more simply, garbage.
Detritus ecosystems are not uncommon. When nutrients from decaying autumn leaves on land are carried by runoff from melting snows into a pond, their consumption by algae in the pond may be checked until springtime by the low winter temperatures that keep the algae from growing. When warm weather arrives, the inflow of nutrients may already be largely complete for the year. The algal population, unable to plan ahead, explodes in the halcyon days of spring in an irruption or bloom that soon exhausts the finite legacy of sustenance materials. This algal Age of Exuberance lasts only a few weeks. Long before the seasonal cycle can bring in more detritus, there is a massive die-off of these innocently incautious and exuberant organisms. Their “age of overpopulation” is very brief, and its sequel is swift and inescapable.2
Living off of such a detritus supply creates a temporary carrying capacity that is much, much higher than the sustainable carrying capacity. The population rises to this level, but it is unsustainable. Eventually, the carrying capacity will drop down to a sustainable level, and when that happens, the population crashes, what ecologists call a die-off.
Equally important is that the temporarily high population diminishes other resources, besides the detritus allowing for their sudden growth. The result of that ecological destruction is that the sustainable carrying capacity is also diminished—in some cases, permanently. When the population crashes, it does not crash to pre-detritus levels, but to levels even lower than that. The reindeer population of St. Matthew island did not crash to the 29 shipped in by the Coast Guard in 1944; it went extinct entirely.
So what does this say about human ecology?
We, too, have seen a phenomenal population spike—and it, too, is a detritus. In this case, our detritus is fossil fuels. When we see the graph of human population growth, we can easily observe that it is identical to the first part of the graph for the St. Matthew reindeer, or the classic overshoot graph.
The phrase “detritus ecosystem” was, of course, not widely familiar. The fact that “bloom” and “crash” cycles were common among organisms that depend on exhaustible accumulations of dead organic matter for their sustenance was not widely known. It is therefore understandable that people welcomed ways of becoming colossal, not recognizing as a kind of detritus the transformed organic remains called “fossil fuels,” and not noticing that Homo colossus was in fact a detritovore, subject to the risk of crashing as a consequence of blooming. …
When the earth’s deposits of fossil fuels and mineral resources were being laid down, Homo sapiens had not yet been prepared by evolution to take advantage of them. As soon as technology made it possible for mankind to do so, people eagerly (and without foreseeing the ultimate consequences) shifted to a high-energy way of life. Man became, in effect, a detritovore, Homo colossus. Our species bloomed, and now we must expect crash (of some sort) as the natural sequel. What form our crash may take remains to be considered in the concluding section.3
Wackernagel et. al have published a study (2002) tracking the progress of humanity’s current overshoot, “Tracking the ecological overshoot of the human economy.”
For each year since 1961, we compare humanity’s demand for natural capital to the earth’s biological productivity. The calculation provides evidence that human activities have exceeded the biosphere’s capacity since the 1980s. This overshoot can be expressed as the extent to which human area demand exceeds nature’s supply: whereas humanity’s load corresponded to 70% of the biosphere’s capacity in 1961, this percentage grew to 120% by 1999. In other words, 20% overshoot means that it would require 1.2 earths, or one earth for 1.2 years, to regenerate what humanity used in 1999.4
It is too late to try to avoid the consequences of ecological overshoot, just as it was too late for the reindeer of St. Matthew island when they looked about and found 6,000 of them on that tiny outcropping of rock, 47 for every square mile of bent willow trees and trampled, overgrazed lichen. Humans are alpha predators. We exist at a very high trophic level. The earth cannot support very many of us. There are currently 16,000 to 30,000 lions (Panthera leo) in the wild, down from some 100,000 in the 1990s.5 Today, there are only 2,500 adult tigers (Panthera tigris) in the wild, while a century ago there was 100,000.6 This gives us an idea of reasonable, global populations for alpha predators. As omnivores, and as we’re able to inhabit much larger parts of the globe than other alpha predators, our numbers will naturally be larger.
There were no census bureaus in Paleolithic times, of course. But by knowing the dependence of early man upon wild food sources, we can make reasonable estimates of maximum feasible average population density, and can estimate the extent of the earth’s land area capable of supporting such hunters and gatherers. The important fact that emerges is that there could never have been very many millions of them. Nevertheless, these early humans were successful; they survived, reproduced, adapted, and continued evolving.
By the time almost 80,000 generations of human hunters and gatherers had lived, their biological and cultural responses to the selection pressures imposed by their spreading habitats had given rise to a descendant population with essentially the inheritable physical traits we see among men and women today. Thus by about 35,000 BC, the humans on earth were of our own species, Homo sapiens. Probably about three million of them were living by gathering and hunting.7
Most importantly, we can note the orders of magnitude difference between populations like these, and our own, current, worldwide population of Homo sapiens of 6.5 billion.
Loss of topsoil, global warming, and mass extinction are natural, predictable results of such overshoot that have all greatly reduced the sustainable carrying capacity when our species, so when we suffer die-off—the now inevitable consequence of actions already in our past—we will not simply die off to the few millions that were once supported. We will be diminished to mere thousands.
Yet, humanity remains one of the most adaptable species this planet has ever seen, and hope remains that our species may endure even this deep, catastrophic folly. It’s unlikely to be a pretty process, but the key to survival is imagination, and the will to consider a life beyond civilization. It is that imagination that will be the greatest consideration—the least abundant resource that will constrain us to Liebig’s law of the minimum.
Loss of topsoil, global warming, and mass extinction are natural, predictable results of such overshoot that have all greatly reduced the sustainable carrying capacity when our species, so when we suffer die-off—the now inevitable consequence of actions already in our past—we will not simply die off to the few millions that were once supported. We will be diminished to mere thousands.
Yet, humanity remains one of the most adaptable species this planet has ever seen, and hope remains that our species may endure even this deep, catastrophic folly. It’s unlikely to be a pretty process, but the key to survival is imagination, and the will to consider a life beyond civilization. It is that imagination that will be the greatest consideration—the least abundant resource that will constrain us to Liebig’s law of the minimum.
See, this is precisely why I believe that some people aware of this should take responsibility for it and choose to die.
Comment by Taylor — 8 September 2006 @ 5:08 PM
We exist at a very high trophic level. The earth cannot support very many of us. There are currently 16,000 to 30,000 lions (Panthera leo) in the wild, down from some 100,000 in the 1990s.5 Today, there are only 2,500 adult tigers (Panthera tigris) in the wild, while a century ago there was 100,000.6 This gives us an idea of reasonable, global populations for alpha predators.
True, but I don’t think those numbers on lions and tigers represent the full number of what those animal populations were pre-civilization. Lions and tigers were hunted down for thousands of years to those populations.
But of course, the general point is true, and that’s more nit-picking.
However, I had always thought the forager carrying capacity (in a healthy ecosystem, obviously) was ten million. Interesting that there is another estimate.
Comment by Taylor — 8 September 2006 @ 5:26 PM
We will be diminished to mere thousands.
Umm… Wow. Thousands as in hundreds of thousands or just thousands?
Also - though arable land will preclude scalable agriculture, there is nothing preventing smaller horticultural get-ups in the immediate future. Not enough to support billions of course, but certainly millions. If the clmiate remains steady enough to support a healthy ecosystem in any location, a well designed horticulture can work there as well.
Granted, I’m not talking about saving civ. Just disputing using foraging numbers only in the context of a post-civ population count.
Comment by MatthewJ — 8 September 2006 @ 7:01 PM
In our present cultural context this reads like madness, but you are probably right, and not the only one to propose this. Yet, I feel that this is a classical case of Prisoner’s Dilemma applied: Those who choose death will do so in vain if the rest of the population keeps on increasing, and for now those who would chooose death as a sensible option are the ones needed to propagate the knowledge about the factors leading to the end of civilization, and of possible alternatives.
Unless, of course, this voluntary die-off is initiated on the level which is commonly called subconscious. Depression leading to suicide may be a natural reaction to the complex, pressing problems weighing heavily on one’s soul. Or men of power keep on deciding everybody’s fate without consulting the victims, leading to involuntary die-off. The necessary means exist, and the necessary mindsets do as well, I suppose.
In the near term, it all seems to depend on the timeframe and the eventual rate of decline in fossile fuel production. In the best of cases, it might suffice to “simply” stop having children, then grow old as a society and finally die of old age, however improbable this option is on a global scale, where not even climate change or the limits in oil supply are agreed-upon facts.
But if things come to a head in 2012–2015, then there is nothing left for us to do, except to try and move in a position which allows us to inherit the remaining wilderness.
(And it still reads like madness.)
Comment by Michael K. — 9 September 2006 @ 6:55 AM
This is going to sound strange but the reason the human population is so high is that we are food for other humans. Capitalism is a form of parasitic canibalism.
parasites feed on the ENERGY of other animals without killing them. The elite of the capitalist class feed of the economic energy of the masses.
There are all these people around, it seems very probable that a predator would evolve the ability to capitalize on this vast resource.
To me it looks more like a situation of a parasite ramping up the metabolism of its host in order to get more energy.
All these individual workers running around destroying the earth are doing so to feed the parasite and not just themselves. They do it for money, in order to survive. The system works so that much of this energy is funneled to the parasite. The parasitic class.
Comment by Ted Heistman — 9 September 2006 @ 4:44 PM
Maybe the parasite will eventually figure out a way to get in blance with the earth. Maybe that is why Rich Elites give money to people like Daniel Quinn and John Abram.
Wouldn’t a newly evolved predator outstrip its rosources also at first?
But as far as the lumpen figuring all this out, I give them as much chance as the caribou.
But maybe the parasites will make decisions to lower the population, conserve resources and things like that. Human husbandry.
Comment by Ted Heistman — 9 September 2006 @ 4:49 PM
Hey J –
Nice article, you covered this topic rather smoothly.
One problem I noticed — and I think it has to do with the assumptions of your sources… it gives the impression that the ‘detrious’ that we are over shooting on is *only* fossil fuels. But of course, we have been doing this for 10K years, not just the last 5o: so the detrious must include topsoil/old growth forest/surface minerals etc.
Janene
Comment by janene — 10 September 2006 @ 9:14 AM
And extinct species.
Comment by JCamasto — 10 September 2006 @ 2:09 PM
Because the number of us even aware of the problem is so much lower than even the reduced carrying capacity, and the problem we’re likely to face is underpopulation?
Yes; humans are not strictly carnivores, but omnivores, and that means we also inhabit lower trophic levels for some of our behaviors, and higher ones for others. We also have a global range, as opposed to geographically-constrained lions and tigers, so of course we’d expect a significantly higher human population—something in the millions, rather than the hundreds of thousands. But this is an order of magnitude difference from the billions we have today, and that’s the most important point: illustrating how far we are today from a sustainable population, i.e., how overshot we are.
Hard to say. I’d like to say hundreds of thousands, but others are afraid with an overshoot this superlative, we may be facing extinction. I think this ignores how amazingly adaptable Homo sapiens is, but we’ve come close to extinction before.
Yes, but as I mentioned, overshoot leaves capacity diminished compared to what it was before. How many of us will actually use horticulture? Horticulture will raise our sustainable carrying capacity to several millions, but I think we’re going to dip well below that, and rise back to it in the first several generations post-collapse.
Granting your argument about capitalism as parasitism (and I don’t think that’s a fundamental element of capitalism any more than the other agricultural economic systems that have exhibited the very same structure, including Communism and feudalism), that cannot explain the growth of humanity, since you’re talking about humans harvesting energy from other humans. That is an entirely internal matter. There can be no growth from that: it would violate the Law of Conservation of Mass-Energy.
Aye, though I think Catton’s fixation on fossil fuels is rooted in a good point: the overwhelming majority of our energy right now comes from that. The other resoruces we tap are vital, but if we’re looking at where our energy comes from, it’s not a very appreciable amount.
Comment by Jason Godesky — 11 September 2006 @ 10:02 AM
Hey –
Oh sure. But how many discussions have had with people that think we want (or that want themselves) to go back to 1900 tech? This will bring it up again, I’d lay money down! (unless we preempt)
Janene
Comment by janene — 11 September 2006 @ 2:40 PM