A new theory has surfaced which purports to explain the deforestation of Rapa Nui (Easter Island) by Polynesians many centuries ago. According to this new account, which has been put forward by archaeologists Carl Lipo of Cal State Long Beach and Terry Hunt of the University of Hawaii, humans did not cut down all the trees on Easter Island. They blame rats for this devastation. Rats stowed away on the boats Polynesians used to reach the island. Bunsen Burner has the story in Easter Island’s large statues hold clues to Rapa Nui’s mysterious past.
Easter Island, famous for its iconic stone heads, has a mysterious past. Known as Rapa Nui in the language of its Polynesian natives, scientists and historians agree that the island was once lushly forested, but the cause of its transformation into the rocky and barren outcrop it is today is a point of debate.
As explained in a recent article in National Geographic, there are two major theories about the island’s transformation. In his 2005 book “Collapse,” UCLA anthropologist Jared Diamond argues that the decline of the island’s forest ecosystem is an example of what he terms “ecocide,” or the devastation of a fragile environment via overuse by humans. Diamond argues that the Polynesians arrived on the island in about AD 800, and began making unlimited use of the island’s forests for fuel and construction. Given the island’s isolated and windy location in the middle of the Pacific, once the forests were gone, the topsoil was quickly blown away. Thus scoured, the rocky land could not recover its original flora.
Archaeologists Carl Lipo and Terry Hunt, of Cal State Long Beach and the University of Hawaii, respectively, suggest another story. They believe that the Polynesians did not arrive until AD 1200, giving the settlers a much shorter time in which to harvest the island’s forests. However, Lipo and Hunt argue that the devastation of the island’s ecosystem was not the result of the human settlers directly, but rather was the work of a stowaway that came along with them—rats.
Based on such evidence as the short time in which the island’s forests disappeared, and physical signs such as marks on recovered palm nuts, Lipo and Hunt say that devastation by an introduced species is more plausible than simple human overuse.
More plausible than simple human overuse?
With no natural predators, and with a plentiful food source in the nuts produced by the island’s palms, the rats quickly overran the island and destroyed its natural balance.
In the wake of this devastation, Lipo and Hunt argue that the settlers are best considered not as rapacious destroyers of the environment, but as ingenious workers who had to make the best of an unintended bad situation...
And now I suppose we can say without fear of contradiction that humans in today's world are not rapacious destroyers of the environment—that would be a wrongheaded view! No, instead it would be best to describe today's humans, all seven billion of them, as ingenious workers who have to make the best of a bad (and certainly) unintended situation. (The "ingenious workers" part refers to how they made and moved the heavy stone statues.)
Climate activist Mark Lynas posted about this alternate Universe on his blog, and allowed Jared Diamond to respond to this new "theory" the devastation of Easter Island. Here's what Diamond said about the rats—
Unfortunately, [Lynas' and other] postings don’t recognize the compelling reasons why Hunt’s and Lipo’s conclusions are considered transparently wrong by essentially all other archaeologists with active programs on Easter Island. I’ll summarize the reasons, for readers interested in these issues:
Rats — the initial reason for positing a role of rats in Easter’s deforestation was that some preserved seeds of Easter’s extinct palm tree, found in caves, show marks of gnawing by rats; and that a study of Hawaii attributed deforestation there to rats.
However, evidence that rats played no significant role in Easter’s deforestation includes the following:
- Rats occur not only on Easter but also on every other one of the hundreds of other Polynesian islands, most of which nevertheless did not end up deforested. Over 90% of preserved palm seeds outside caves were not gnawed by rats.
- Easter’s forest consisted not only of the palm but also of at least two dozen other species of trees and other plants, all of which also became extinct on Easter although most of them are not known to suffer seed predation by rats and continue to exist in the presence of rats on other Polynesian islands.
- The Hawaii study does not demonstrate, but merely speculates about, a role of rats in deforestation on Hawaii. Had rat predation on seedlings caused deforestation on Easter, there should then have been no regeneration of young palm trees, but continued survival of mature palms capable of living for many centuries. Instead, palm trees continued to regenerate for centuries in the presence of rats, but eventually all palms, young and old, disappeared by AD 1600.
- The reason for their disappearance is obvious: they were cut and burned by humans, as shown by burned palm stumps, cleanly-cut-off palm stumps, burnt palm leaves, and burned soil in many parts of Easter Island. See the attached paper by Mieth and Bork, which Hunt and Lipo did not even cite in their book.
And now let us turn to deforestation in contemporary times. It seems there is a dispute about what the role of intensive deforestation has been in causing rising CO2 emissions. Brad Plummer of the Wonk Blog wrote the story up in The mystery of tropical deforestation — in two maps.
[My note: Humans don't cut down trees. Countries cut down trees.]
These trees and soil contain huge reservoirs of carbon, and, as they get cleared and burned, they release heat-trapping greenhouse gases into the air. But how much carbon gets kicked up, exactly, has always been a bit of a puzzle.
In its 2007 report, the Intergovernmental Panel on Climate Change estimated that tropical deforestation accounted for roughly 20 percent of the world’s global-warming emissions. But there was an asterisk next to these estimates. They were based on self-reported data from countries themselves. Some nations, like Brazil, do a solid job of tracking deforestation. Other countries, particularly poorer ones in Africa, lack the resources and manpower to monitor their rain forests. They essentially have to guess, extrapolating from data that’s often years out of date.
So, more recently, scientists have turned to satellite monitoring to offer a clearer picture of which forests are actually being chopped down. In a new study published in Science, a team of nine researchers — led by Nancy Harris of Winrock International — pored over satellite data and estimated that tropical deforestation accounted for about 10 percent of all greenhouse gas emissions between 2000 and 2005.
That’s lower than previous estimates...
More valuable still, the researchers were able to create a more precise map of where the most intensive deforestation was occurring. Roughly 55 percent came from Brazil and Indonesia. Note that this map doesn’t measure the loss of peatlands, which can account for half the greenhouse-gas emissions in Indonesia in some years.
Well, I hate to throw a wrench into the works here, but I've got an alternate theory about how tropical deforestation comes about.
It's rats who are killing those trees! They're eating all the seeds. It's not us!
Ignore that guy with the chainsaw pictured above. Ignore the people who paid him to cut down those trees so they could create another profitable palm tree plantation. (Palm oil is used predominantly for cooking, but also to make biodiesel.) Ignore the corrupt Indonesian government officials who were paid to look the other way. No, no, no! Rats are the ones causing all this ecological devastation.
OK, I've got a theory. All I need now is some evidence—any evidence will do!—to support it. Otherwise, my "rats theory" will be yet another futile attempt to get humans off the hook. Just like Easter Island.