A couple of years ago I wrote an article titled "How Civilizations Fall: A Theory of Catabolic Collapse" -- quite the cheerful topic, granted, but it's relevant nowadays in more than an academic sense. I've never been able to find much common ground with the neoprimitivist types who insist that civilization is an awful idea and we all ought to go back to hunting and gathering, but there isn't much encouragement to be had from the cheerleaders of perpetual progress, either. In ecological terms, civilization is quite a new thing, not much more than 10,000 years old at most, and like most new evolutionary gambits, it's had its share of drastic ups and downs. Visit cities in Italy, China, or elsewhere that have been continuously inhabited for 2500 years and it's clear that, in the right environmental conditions, the civilized way of life can sustain itself over the long term; visit the ruins of Ur of the Chaldees or the Mayan metropolis of Tikal and it's equally clear that when environmental conditions don't support it, civilization is a mayfly phenomenon that flits past and vanishes in a blink of ecological time.
The question on many minds these days is whether our current industrial civilization falls into one of these categories or the other. It's a fair question, and one that a steady look at the ecological processes behind the fall of other civilizations can help answer. That was the motive behind the paper. In its original form, though, it bristles with equations, footnotes, and all the other impedimenta of the modern academic paper -- it was intended for publication in a peer-reviewed journal in the field of human ecology, a destiny it hasn't yet managed to achieve -- and to judge by the questions I've fielded since it appeared online last year, not all its readers have been able to hack their way through the scholarly undergrowth to the ideas at the core.
The idea of catabolic collapse is simple enough, and it's best communicated through a metaphor. Imagine that, instead of the fate of civilizations, we're discussing home ownership. Until recently, when people went shopping for a home, most of them were sensible about it and bought one within their means. The housing bubble of the last few years, though, encouraged quite a few people to get in over their heads, buying much more house than they could afford, on the assumption that appreciating real estate values and the other advantages of home ownership would make up the difference.
If you're one of these latter, though, you probably didn't take the time to work out just how much your huge new McMansion would cost to own, maintain, and repair, and you almost certainly didn't realize that every period of rising real estate values gives way to a period of stagnant or falling values sooner or later. As these realities begin to sink in, you find yourself in a very awkward bind, because your monthly paycheck doesn't cover all your monthly expenses. You can cover the difference for a while by refinancing your house and extracting any extra equity in cash, but that only works as long as interest rates keep dropping and home values keep rising. Once that option's closed off, you've got very few others as long as you plan on keeping the house. You can take on more debt, which means your bills go up; you can postpone maintenance and repairs, which means your house begins to fall apart, and your bills go up; or you can stop paying some of your bills, which means your house becomes much less livable, and your bills go up. Eventually you end up so deep in the hole that you can't pay the mortgage and the property taxes any more, and you lose the house.
That's catabolic collapse in a nutshell. Like suburban mansions, civilizations are complex, expensive, fragile things. To keep one going, you have to maintain and replace a whole series of capital stocks: physical (such as buildings), human (such as trained workers), information (such as agricultural knowledge), social (such as market systems), and more. If you can do this within the "monthly budget" of resources provided by the natural world and the efforts of your labor force, your civilization can last a very long time. Over time, though, civilizations tend to build their capital stocks up to levels that can't be maintained; each king (or industrial magnate) wants to build a bigger palace (or skyscraper) than the one before him, and so on. That puts a civilization into the same bind as the homeowner with the oversized house.
What happens then depends on whether the civilization's most important resources are sustainable or not. Sustainable resources are like a monthly paycheck; you've got to live within it, but as long as you can keep expenses on average at or below your paycheck, you know you can get by. If a civilization gets most of its raw materials from ecologically sound agriculture, for example, the annual harvest puts a floor under the collapse process. Even if things fall apart completely -- if the homeowner goes bankrupt and has his house foreclosed, to continue the metaphor -- that monthly paycheck will let him rent a smaller house or an apartment and start picking up the pieces. Civilizations such as ancient Egypt and imperial China, which were based on sustainable resources, cycled through this process many times, from expansion through overshoot to a self-limiting collapse that bottomed out when capital stocks got low enough to be supported by the steady resource base.
If the civilization depends on unsustainable resource use, though, the situation is a lot more serious. In terms of the metaphor, our homeowner bought the house with lottery winnings, not a monthly paycheck; his income is only a fraction of the amount he spends each month -- and not necessarily a large fraction, either. The process that leads to foreclosure is different, too. Our lottery winner can spend as freely as he wants, up to the point that his bank balance drops far enough that his checks start bouncing. By the time he runs into that limit, though, the chance to do anything about the situation is long past. The money is gone, he's faced with bills his monthly income won't even begin to cover, and by the time the collection agencies get through with him he may very well end up on the street. Civilizations such as the Classic Maya, which used core resources (in the Maya case, the fragile fertility of tropical soils) unsustainably, went through this process, and the "collection agencies" of nature left nothing behind but crumbling ruins in the Yucatan jungle.
This is not good news for our modern industrial civilization, of course, because its capital stocks are supported by winnings from the geological lottery that laid down fantastic amounts of fossilized solar energy in the form of coal, oil, and natural gas. Even the very small fraction of our resource base that comes from the "paycheck" of agriculture, forestry, and fishing depends on fossil fuels, and is being used up at unsustainable rates. Since the late 1950s, scientists have been warning that what's left of our fossil fuel resources won't sustain our current industrial system indefinitely, much less support the Utopia of perpetual economic growth promised by pundits across the political spectrum. For the most part, these warnings have been roundly ignored. If they continue to be ignored until actual shortages begin, we may be in for a very ugly future.
That future may be closer than most people like to think, too. The collapse of New Orleans after Hurricane Katrina drew attention from around the world, but few people seem to have noticed the implications of the Big Easy's fate. The United States has suffered catastrophic hurricanes and other natural disasters before, and always in the past the disaster was promptly followed by a massive rebuilding program. Not this time. The French Quarter and a few other mostly undamaged portions of the city have reestablished a rough equivalent of their former life, but much of the rest of the city has been bulldozed or simply abandoned to the elements. The ruins of the Ninth Ward, like the hundreds of abandoned farm towns that dot the Great Plains states and the gutted cities of America's Rust belt, may be a harbinger of changes most Americans will find it acutely uncomfortable to face.
One place where the housing metaphor breaks down, though, is that a civilization has a fractal structure -- that is, the same patterns that define it at the topmost level also take form on smaller scales. The long-lasting cities in Italy and China mentioned at the beginning of this essay maintained urban life through the fall of empires precisely because of this fractal structure; a single city and its agricultural hinterland can survive even if the larger system comes apart. The recent spread of Peak Oil resolutions and projects by cities and towns across America is thus a very hopeful sign. It's going to take drastic changes and a great deal of economic rebuilding before these communities can get by on the more limited resources of a deindustrial future, but the crucial first steps toward sustainability are at least on the table now. If our future is to be anything but a desperate attempt to keep our balance as we skid down the slope of collapse and decline, these projects may well point the way.