Those dirty Polynesian rats

I'm a big fan of Jared Diamond's Guns, Germs and Steel, and still need to read his sequel, Collapse. However, Terry L. Hunt has an essay in the latest issue of The American Scientist that calls into question Diamond's central case study in Collapse -- the decline and fall of the Rapa Nui on Easter Island: In the prevailing account of the island's past, the native inhabitants?who refer to themselves as the Rapanui and to the island as Rapa Nui?once had a large and thriving society, but they doomed themselves by degrading their environment. According to this version of events, a small group of Polynesian settlers arrived around 800 to 900 A.D., and the island's population grew slowly at first. Around 1200 A.D., their growing numbers and an obsession with building moai led to increased pressure on the environment. By the end of the 17th century, the Rapanui had deforested the island, triggering war, famine and cultural collapse. Jared Diamond, a geographer and physiologist at the University of California, Los Angeles, has used Rapa Nui as a parable of the dangers of environmental destruction. "In just a few centuries," he wrote in a 1995 article for Discover magazine, "the people of Easter Island wiped out their forest, drove their plants and animals to extinction, and saw their complex society spiral into chaos and cannibalism. Are we about to follow their lead?" In his 2005 book Collapse, Diamond described Rapa Nui as "the clearest example of a society that destroyed itself by overexploiting its own resources." Two key elements of Diamond's account are the large number of Polynesians living on the island and their propensity for felling trees. He reviews estimates of the island's native population and says that he would not be surprised if it exceeded 15,000 at its peak. Once the large stands of palm trees were all cut down, the result was "starvation, a population crash, and a descent into cannibalism." When Europeans arrived in the 18th century, they found only a small remnant of this civilization.... When I first went to Rapa Nui to conduct archaeological research, I expected to help confirm this story. Instead, I found evidence that just didn't fit the underlying timeline. As I looked more closely at data from earlier archaeological excavations and at some similar work on other Pacific islands, I realized that much of what was claimed about Rapa Nui's prehistory was speculation. I am now convinced that self-induced environmental collapse simply does not explain the fall of the Rapanui. Radiocarbon dates from work I conducted with a colleague and a number of students over the past several years and related paleoenvironmental data point to a different explanation for what happened on this small isle. The story is more complex than usually depicted. The first colonists may not have arrived until centuries later than has been thought, and they did not travel alone. They brought along chickens and rats, both of which served as sources of food. More important, however, was what the rats ate. These prolific rodents may have been the primary cause of the island's environmental degradation. Using Rapa Nui as an example of "ecocide," as Diamond has called it, makes for a compelling narrative, but the reality of the island's tragic history is no less meaningful.... There is no reliable evidence that the island's population ever grew as large as 15,000 or more, and the actual downfall of the Rapanui resulted not from internal strife but from contact with Europeans. When Roggeveen landed on Rapa Nui's shores in 1722, a few days after Easter (hence the island's name), he took more than 100 of his men with him, and all were armed with muskets, pistols and cutlasses. Before he had advanced very far, Roggeveen heard shots from the rear of the party. He turned to find 10 or 12 islanders dead and a number of others wounded. His sailors claimed that some of the Rapanui had made threatening gestures. Whatever the provocation, the result did not bode well for the island's inhabitants. Newly introduced diseases, conflict with European invaders and enslavement followed over the next century and a half, and these were the chief causes of the collapse.... I believe that the world faces today an unprecedented global environmental crisis, and I see the usefulness of historical examples of the pitfalls of environmental destruction. So it was with some unease that I concluded that Rapa Nui does not provide such a model. But as a scientist I cannot ignore the problems with the accepted narrative of the island's prehistory. Mistakes or exaggerations in arguments for protecting the environment only lead to oversimplified answers and hurt the cause of environmentalism. We will end up wondering why our simple answers were not enough to make a difference in confronting today's problems. Ecosystems are complex, and there is an urgent need to understand them better. Certainly the role of rats on Rapa Nui shows the potentially devastating, and often unexpected, impact of invasive species. I hope that we will continue to explore what happened on Rapa Nui, and to learn whatever other lessons this remote outpost has to teach us.