I saw Jared Diamond speak last night about his [relatively] new book Collapse. He talked about ecological criteria for a sustainable society and offered examples of societies that overcame serious environmental problems, such as deforestation in Tokugawa Japan and the shogunate development of more sustainable forestry techniques. He also talked about societies that failed to meet the requisite ecological criteria for sustainability, and eventually collapsed.

The most interesting story Diamond told, and the one to which he devoted the largest amount of time, was that of Easter Island. Most people have seen pictures of the massive statues erected by Easter Islanders, a people with no metal tools, no large domesticable animals, and no access to the outside world. These statues weigh between 10 and 270 tons, and were erected with nothing but ingenuity, manpower, and trees.

Lots and lots of trees.

Image courtesy of http://www.asahi-net.or.jp/~yf5f-wtnb/

The now-extinct giant palm trees of Easter Island were used to build log "sleds" on which the massive statues were transported down from the quarry to the coast. Their bark was used to weave of the rope necessary to haul the sleds. The were also necessary for more mundane uses, such as carving of canoes for fishing and constructing the homes in which the islanders lived.

The apparent voracity with which the islanders carved and erected the statues was no match for the small size of the island and its forest of giant palms. After the last giant palm was felled, effectively ending the islanders' ability to put up statues, to make the canoes that allowed them to fish, or to build homes, the tribes descended into war and cannibalism. By the time Easter Island was discovered by Europeans in 1722, it was utterly devoid of not only giant palms, but of any plant taller than a person. Its population had plummeted to about one fifth of its historical maximum of about 15,000 attained in the sixteenth and seventeenth centuries.

The most compelling part of Diamond's lecture was a question that he maintains was first posed to him by one of his undergraduate students at UCLA (though it appears in several articles penned by Diamond as early as 1995, and no doubt in Collapse as well): "What was the Easter Islander who cut down the last palm tree thinking while he was doing it?"

All of the possible responses that Diamond offered had familiar ring:

"Technology will solve our problems."

"This is my private property; I have a right to do with it as I please!"

"How do we know that cutting down all the trees will cause a problem? There's no conclusive evidence!"