The Unkindest Cut

Yesterday we took up Jared Diamond’s discussion of Easter Island in his latest book, Collapse: How Societies Choose to Fail or Succeed. The book, as I suppose anyone who hasn’t just been stunned by a blow to the head might gather from the title, looks at societies that have failed, contrasts them with others that have not, and attempts to explain the difference.

In the case of the isolated Easter Island civilization, the complete deforestation of the island seems to have been the proximate cause of their catastrophic decline. Things got so bad in those dark days that the population was driven to cannibalism, and it is understandable that the modern descendants of this community are a little defensive about their ancestor’s stewardship of their island. After all, as Diamond asks, what goes through a person’s mind as he cuts down the last tree in the world? The modern-day islanders prefer to account for the denudation of the island by invoking climatic changes that were simply beyond the inhabitants’ control. The archaeological record, however, doesn’t support this explanation — there had been many cool dry spells in Easter’s history, and the forests had survived for hundreds of thousands of years. It seems hard to avoid the conclusion that the Easter Islanders were just incomprehensibly foolish. After all, there are lots of other isolated, inhabited islands all over Polynesia, and Easter’s deforestation was by far the worst (it would have been hard to outdo, as there was literally not a single tree left standing anywhere on the island).

But Diamond tends toward the view that people are generally the same as regards their average cleverness (he makes a strong argument in Guns, Germs, and Steel: The Fates of Human Societies that the differential success of First World cultures was due not to any innate differences, but rather to the luck of the geographical draw), so he went looking for other factors that might have played a role in Easter’s unique misfortune. He and his research partner Barry Rolett examined other Polynesian islands, and made statistical analyses of their levels of deforestation in combination with nine significant parameters. They they found that deforestation is more severe on:

  • dry islands than wet islands
  • cold high-latitude islands than warm tropical islands
  • old volcanic islands than young volcanic islands
  • islands without aerial ash fallout than with it
  • islands far from Central Asia’s dust plume than near it
  • islands without makatea than with it
  • low islands than high islands
  • remote islands than islands with near neighbors
  • small islands than big islands

Many of these factors are just as you’d expect. Obviously a warmer, wetter climate is more favorable to plant growth. New volcanic islands have rich soil, but the nutrients leach out over time. Airborne ash and dust tend to replenish what is lost in this way, and there there are large swaths of the Pacific that are in the path of such wind-driven plumes. A more vertical terrain generally means that there are more places that are not suitable for gardening, and so won’t be cleared, and it also means that there will tend to be more places that are hard to get to, where trees will not be cut. The economy of island cultures is often supported by fishing, meaning that the population size that an island can support is in linear proportion to its shoreline. A small island, having a smaller ratio of land area to coastline, will tend to have a higher overall population density, which places more of a strain on inland resources. People living on remote islands are more likely to stay home and have a large impact on their local environment than those who can travel freely for trading, war, and resettlement. Finally, there is makatea, which is an exposed coral terrain found on some Polynesian islands. It is jagged, deeply fissured, and almost impossible to walk over, and its presence would certainly tend to inhibit the carrying of logs (or anything else), and would isolate areas where trees might safely grow.

So how does Easter look in terms of these factors? As it happens, the island is low, cool, dry, old, far from the Pacific ash and dust plumes, small, extremely remote, and devoid of makatea. In other words, although it was well-forested in its pristine state, it scored high on every identified risk factor, and was in fact a very delicate ecosystem; trouble waiting to happen. I am sure that the present-day islanders can take some comfort in Diamond’s findings.

Like Guns, Germs, and Steel, this is a fascinating book, and I expect I’ll have more to say about it soon. Recommended reading.

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