Overshoot was one of the first books to declare the need to understand human society and its history in terms of a fully ecological paradigm. The book's central thesis is the following:
Catton contends that "the past four centuries of magnificent progress were made possible by two non-repeatable achievements: (a) discovery of a second hemisphere, and (b) development of ways to exploit the planet's energy savings deposits, the fossil fuels." He explains that, rather than increasing the earth's permanent carrying capacity, the exploitation of fossil fuels has actually made the situation worse by providing the illusion that carrying capacity has been increased. In response to this illusion of increased carrying capacity, human populations have grown at an exponential rate--far beyond the true (i.e., permanent/sustainable) carrying capacity defined by the total amount of land and renewable resources on the earth.Human beings, in two million years of cultural evolution, have several times succeeded in taking over additional portions of the earth's total life-supporting capacity, at the expense of other creatures. Each time, human population has increased. But man has now learned to rely on a technology [fossil fuels] that augments human carrying capacity in a necessarily temporary way--as temporary as the extension of life by eating the seeds needed to grow next year's food. Human population, organized into industrial societies and blind to the temporariness of carrying capacity supplements based on exhaustible resource dependence, responded by increasing more exuberantly than ever, even though this meant overshooting the number our planet could permanently support. Something akin to bankruptcy was the inevitable sequel.
One of the more unique contributions Catton makes in Overshoot is to frame the ecological predicament in a sociological context, summarizing five key perspectives along a sort of "denial spectrum" that various people have in regards to humans' ecological predicament:
- 1. Ostrichism: Insisting that the assumption of limitlessness was and still is valid
- 2. Cynicism: Not believing that the New World's newness once did, or that its oldness now does, have any significance
- 3. Cosmeticism: Having faith that relatively superficial adjustments like family planning, recycling centers, and anti-pollution laws will keep the New World new and perpetuate the Age of Exuberance
- 4. Cargoism: Having faith that technological progress will stave off major institutional change
- 5. Realism: Recognizing that the New World is old and that major change must follow
One of the key points of this book is that, while Homo sapiens is certainly unique among the animals in its being able to understand and react to its ecological predicaments, it is not "above" ecological reality. It is too late for us to use our uniquely human abilities to prevent overshoot and the resulting population crash. The best we can do at this point is to recognize the inevitability of the eventual crash (excepting a Cargoist deus ex machina fantasy such as "free energy") and adjust our cultural paradigms to reflect this ecological fact so that when the crash comes, it will not be falsely blamed on human scapegoats. Failing to make this basic cultural preparation could be far more disastrous than even the inevitable population crash.