(This is Part 19 of a series. Go back to Part 18.)
A very interesting society that Jared Diamond talks about is the Anasazi peoples of the Southwestern United States, who existed from about 600 AD to about 1150 AD. They inhabited the huge Chaco Canyon of New Mexico and surrounding areas for about 50 miles out.
The Anasazi built hundreds of miles of roads and constructed the tallest buildings in pre-Columbian North America. They enjoyed a thriving civilization. So what happened? Why did they collapse?
The Anasazi inhabited a vast valley set in Chaco Canyon. It was filled with pinyon trees, a beautiful and hardy variety of tree that provided the Anasazi with a variety of services:
First, the living trees provided shade, beauty, rain and pinyon nuts. But the Anasazi discovered that, as useful as the trees were alive, they were even more valuable when cut down. Then the trees provided lumber for buildings, they provided firewood for fires—and most of all, cutting the trees cleared the land for growing corn, the staple of their diet.
The civilization became so successful that gradually all the trees were gone in Chaco Canyon. No matter, because lumber and firewood, etc. could be brought in from the surrounding areas as the Anasazi extended their influence over wider regions.
Now the huge valley was used mostly for farming, and was able to grow the corn and beans that were the mainstay of the diet. Over time, though, with less and less tree cover, flooding became more frequent and the soil began to degrade. The soil lost nutrients and/or rained away through deep gullies formed in the denatured land.
So the Anasazi woke up one morning and discovered that they could no longer grow food in Chaco Canyon. But no matter—because they could import their food—along with lumber, pottery, turqoise and everything else—from the surrounding areas, which they controlled.
The Anasazi reached their peak around 1050 to 1100 AD. However, their economy was unsustainable because it was being powered now by going further and further into overshoot.
That is, trees in the whole surrounding area were now being cut at a rate faster than they could regenerate. The soil was blowing away and washing away far faster than it could be regenerated. And it was losing nutrients. The Anasazi reached a point where their economy was being powered by a use of their ecology beyond its carrying capacity.
Though Anasazi society was now in overshoot, it was not noticeable right away. That is one of the features of overshoot, that the effects don't normally show up right away. Rather, they show up after a delay.
For instance, if we've drunk too much alcohol in the evening, we don't normally notice it that evening. Instead, we notice the outcome, our hangover, the next morning. There's a delay between the overshoot and the outcome.
Similarly, when the enormous banks of codfish were overfished off the Newfoundland coast, the effects were not seen right away. Though cod were being caught much faster than they could regenerate, the catch stayed steady for some years while the overall stock was declining. But then, as overshoot continued, the Newfoundland cod fishery collapsed.
Something not dissimilar happened to the Anasazi. Ecologically, they were "living beyond their means," as it were, but the effects were not noticeable right away because the economy continued to thrive. But internally the economy was weakening because it was becoming more and more fragile—dependent now upon a smaller and smaller base of woodlands and fertile soil.
Then a series of droughts hit, beginning in 1029. In earlier years, when the population was smaller and its impact upon the environment was less, the Anasazi could have weathered the droughts.
But now, having overused their ecological resources for so long, they couldn't meet this challenge. According to archaeologists, as the effects of overshoot started becoming felt and food and other goods became more scarce, the Anasazi descended into a series of conflicts, wars and civil unrest—the normal process.
Now the Anasazi fought each other over increasingly scarce resources. Some were killed in various conflicts; others starved. And the Anasazi civilization ceased to exist.
That is the danger of overshoot: If not managed wisely so that the society is skillfully (and fairly quickly) brought down below the carrying capacity of its ecology, then the overshoot reaches a point where the society can no longer avoid a serious decline, which can arrive quite suddenly and precipitously.
That is the current challenge to the human race. We are already in overshoot on the planet by about 20%, according to scientists, and in spite of various efforts humanity is steadily increasing its ecological footprint on the planet.
The result could be similar to other examples in our history, only on a much larger scale: If we cannot find a way to pretty rapidly bring ourselves under the carrying capacity of the earth then human society could, in just a few decades, suffer a sudden and surprising collapse.
(This is the end of Part 19. Go to Part 20.)
—jim sloman, 5.11.07
|
