The story of Rapa Nui (better known as Easter Island), consisting of 63 square miles located 2,300 miles west of Chile, is one of enduring interest. How a lush island became a wasteland denuded of its trees, bereft of most of its population, and finally ended up primarily as a home for gigantic stone statues, is a mystery that has intrigued scientists for years.

Was the collapse of that community due to internal factors because of its inhabitants being too cavalier with its resources in their obsession with building and transporting the statues? Or was it due to external factors, primarily the impact of Europeans who brought diseases (smallpox, syphilis, and tuberculosis) and other problems that the islanders could not deal with? I have been intrigued by this question for some time and have written about it repeatedly.

Those who favor the first explanation have used Rapa Nui as a model for what could happen to the Earth if we too don’t take care of our resources, that we too could be confronted with a sudden collapse of our ecosystem. Jared Diamond’s book Collapse treats the island story that way.

A new paper says that it is not that simple. The authors took soil samples from across the island and used them to get both a temporal and geographic distribution of events and their results can be seen here. The article is behind a subscription paywall but a good description of what it contains can be read at Machines Like Us.

The paper says that both internal and external reasons contributed to the collapse. Here is the abstract:

Many researchers believe that prehistoric Rapa Nui society collapsed because of centuries of unchecked population growth within a fragile environment. Recently, the notion of societal collapse has been questioned with the suggestion that extreme societal and demographic change occurred only after European contact in AD 1722. Establishing the veracity of demographic dynamics has been hindered by the lack of empirical evidence and the inability to establish a precise chronological framework. We use chronometric dates from hydrated obsidian artifacts recovered from habitation sites in regional study areas to evaluate regional land-use within Rapa Nui. The analysis suggests region-specific dynamics including precontact land use decline in some near-coastal and upland areas and postcontact increases and subsequent declines in other coastal locations. These temporal land-use patterns correlate with rainfall variation and soil quality, with poorer environmental locations declining earlier. This analysis confirms that the intensity of land use decreased substantially in some areas of the island before European contact.

The paper itself concludes as follows:

New chronometric evidence from three study areas reveals spatial and temporal variation in Rapa Nui land use. Initial settlement and expansion occurred from ca. AD 1200, with the rapid development of the interior for agricultural activities beginning in the early AD 1300s. Reductions in the intensity of land use before European contact in the dry northwest section of Rapa Nui and the region of nutrient-leached soils in upland areas would have contributed to increasing land pressure in other parts of the island and may have led to periods of conflict as land use was renegotiated.

This temporal reconstruction of land-use history associated with food production argues against the notion of an island-wide precontact collapse as a useful explanatory concept for Rapa Nui—although it does support the reality of a precontact decline in land use that probably was associated with declines in food production. These results indicate that island-wide landscape use was modulated by an underlying climatic and biogeochemical matrix as well as by response to dynamic variations in climatic and biogeochemical factors. We propose that precontact declines in the intensity of land use (and presumably population) in dry and infertile regions of Rapa Nui better reflect a framework of environmental constraint than of environmental degradation—although constraint and degradation can intergrade, as in the case of infertile soils that are suitable for shifting cultivation being degraded through overuse.

Whatever the final conclusions about the causes of the decline of Rapa Nui turn out to be, it is still a sobering warning to us that we have to be careful of not taxing the Earth’s resources too heavily if we don’t want our descendants to have to cope with a devastated landscape.