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THE LANGUAGE OF ECOLOGY

IN THE LANGUAGE OF ECOLOGY—a language which it behooves us all to learn—the conditions of an imperiled environment are described in a few short and pungent words: 'drawdown,' 'overshoot,' 'crash,' and 'die-off.'

"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.

"Overshoot is the inevitable and irreversible consequence of continued drawdown, when the use of resources in an ecosystem exceeds its carrying capacity and there is no way to recover or replace what was lost. It takes many forms, depending on the system, but perhaps the clearest and in some ways the most touching is exemplified by Easter Island. When it was first settled a thousand years ago, the island was a rich and forested land covered with palms and a small native tree called the sophora, and on its sixty-four square miles a prosperous and literate culture developed organizational and engineering skills that enabled it to erect the famous massive stone statues all along the coastline. For reasons lost in time, the population of the island over the years increased to something like 4,000 people, apparently necessitating a steady drawdown of vegetation that eventually deforested the entire island and exhausted its fertile soils. Somewhere along the line came overshoot, unstoppable and final, and then presumably conflict over scarce food acreage, and ultimately warfare and chaos. By the time of Captain Cook's voyage to the island in the 1775 there were barely 630 people left, eking out a marginal existence; a hundred years later, only 155 islanders remained.

"Crash, as with the Easter Islanders, is what happens after overshoot—a precipitate decline in species numbers. Once a population has exceeded the capacity of its environment in one life-giving respect or another, there is no recourse, nothing to be done until that population is reduced to the level at which the resources can recover and are once again adequate to sustain it. Take the case of the famous Irish potato famine. For well over a century, year after steady year, the British encouraged and the Irish developed a near-total dependency upon a single dietary mainstay, the potato, and the population of the island grew from 2 million people to more than 8 million. Then suddenly in 1845 a natural competitor for the potato came along in the form of a parasitic fungus that got to the tubers somewhat before the people did and turned the potatoes into sticky, inedible, mucous globs. Crash: within a generation the country was devastated, more than half the population died or emigrated, and those who remained were reduced to a poverty that diminished only a century later.

"Die-off and, in its final form, die-out, is a phenomenon common in the history of zoology and botany, and the dodo and the passenger pigeon are not exceptional. There is, for example, the everyday but suggestive experience of yeast cells introduced into a wine vat. Enormously successful as a species, they gobble up nutrients from the sugary crushed grapes around them and expand their population without a thought to the consequences of drawdown; within weeks, however, the 'pollution' they produce—alcohol and carbon dioxide, which of course is what the fermentation is all about—have so filled their environment that they are unable to survive. The resulting crash, in that vat at least, means an acute die-off and then extinction.

"Where along this ecological trajectory can we locate the modern—the theoretically sapient—human?" [p.p. 24-26]

 

[Graphs from CCN, Spring, 1992]

DWELLERS IN THE LAND, by Kirkpatrick Sale; New Society Pub., 1991, Phone: 800-253-3605; ISBN 0-86571-225-5.


GARRETT HARDIN
on carrying capacity

"Transgressing the carrying capacity for one period lowers the carrying capacity thereafter, perhaps starting a downward spiral toward zero. David Klein's classic study of the reindeer on St. Matthew Island illustrates the point.26 In 1944 a population of 29 animals was moved to the island, without the corrective feedback (negative feedback) of such predators as wolves and human hunters. In 19 years the population swelled to 6,000 and then "crashed" in 3 years to a total of 41 females and one male, all in miserable condition. Klein estimates that the primeval carrying capacity of the island was about 5 deer per square kilometer. At the population peak there were 18 per square kilometer. After the crash there were only 0.126 animals per square kilometer and even this was probably too many once the island was largely denuded of lichens. Recovery of lichens under zero population conditions takes decades; with a continuing resident population of reindeer it may never occur. Transgressing the carrying capacity of St. Matthew Island reduced its carrying capacity by at least 97.5 percent. It is facts like these -- repeated over and over again in game management experience -- that justify the ecolate game manager in viewing carrying capacity as partaking of the sacred. I do not think it is going too far to assert and defend the sanctity of the carry capacity. "

AN ECOLOATE VIEW OF THE HUMAN PREDICAMENT, G. Hardin; in McRostie, ed. GLOBAL RESOURCES: Perspectives and Alternatives Baltimore: University Park Press, 1980.