"Drawdown is the process by which the dominant species in an ecosystem uses up the surrounding resources faster than they can be replaced and so ends up borrowing, in one form or another, from other places and other times. For our age, though the examples of such depletion are numerous, the most vivid is that of fossil fuels. In the space of a little more than a hundred years we have used up perhaps 80 percent of the buried remains of the Carboniferous period--oil, gas, and coal--that were deposited over a period of a hundred million years or more, and what's more we have become totally dependent on continuing the process. One can argue about the due-date, but the outcome is certain." Dwellers in the Land, Kirkpatrick Sale