Easter Island (alternatively Rapa Nui) is a Polynesian island in the southeastern Pacific Ocean, at the southeasternmost point of the Polynesian triangle. Easter Island is noted for its monumental prehistoric statues and for the sudden collapse of the Rapanui society. The inhabitants of Easter Island maintained a functional society for centuries before some force caused the island's ecosystem as well as their cultural system to be devastated.
This collapse is of great interest to scientists as the sustainability of civilization on islands may be analogous to that of the global community. The hypothesis is that island sustainability is narrow enough in scope that analysis will yield critical data for application to the broader world. Unfortunately, it has proved difficult for the scientific community to form a consensus on the cause for societal collapse, even in a setting as delimited as Easter Island.
Location and physical properties
Easter Island is one of the world's most isolated inhabited islands. It is 3600 kilometers (2237 mi) west of continental Chile and 2075 km (1290 mi) east of Pitcairn (Sala y Gómez, 415 kilometers to the east, is closer but uninhabited). It has a latitude close to that of Caldera, Chile, an area of 163.6 km² (63 sq mi), and a maximum altitude of 507 meters. There are three Rano (freshwater crater lakes), at Rano Kau, Rano Raraku and Rano Aroi, near the summit of Terevaka, but no permanent streams or rivers.
Easter Island exhibits low relief topography, low inputs of soil-enriching continental dust, and little or no volcanic ash fallout. The island experiences some rainfall year-around, although it is substantially drier than islands in the western Pacific. The climate is subtropical, with southeast trade winds from October to April. Annual rainfall verages 1250 millimeters (mm), with a rainy season occurring in the winter. Average temperatures range from 19 ºC in winter to 24 ºC in summer.
Early European visitors to Easter Island recorded the local oral traditions of the original settlers. In these traditions, Easter Islanders claimed that a chief Hotu Matu'a arrived on the island in one or two large canoes with his wife and extended family. They are believed to have been Polynesian. There is considerable uncertainty about the accuracy of this legend as well as the date of settlement. Published literature suggests the island was settled around 300-400 AD, or at about the time of the arrival of the earliest settlers in Hawaii. Some scientists say that Easter Island was not inhabited until 700-800 AD. This date range is based on radiocarbon dates from charcoal that appears to have been produced during forest clearance activities. Moreover a recent study which included radiocarbon dates from what is thought to be very early material suggests that the island was settled as recently as 1200 AD. This seems to be supported by a 2006 study of the island's deforestation, which could have started around the same time. Any earlier human activity seems to be insignificant if there was any at all.
The Austronesian Polynesians, who first settled the island, are likely to have arrived from the Marquesas Islands from the west. These settlers brought bananas, taro, sweet potato, sugarcane, and paper mulberry, as well as chickens and Polynesian Rats. The island at one time supported a relatively advanced and complex civilization.
Moai (or mo‘ai) are monolithic human figures carved from rock on Easter Island between 1250 and 1500 AD. Nearly half are still extant at Rano Raraku, the main moai quarry, but hundreds were transported from there and set on stone platforms called Ahu around the island's perimeter. Almost all moai have overly large heads three-fifths the size of their bodies. The moai are chiefly the 'living faces' (aringa ora) of deified ancestors. The statues still gazed inland across their clan lands when Europeans first visited the island, but most would be cast down during later conflicts between clans.
The statues' production and transportation is considered a remarkable intellectual, creative, and physical feat. The tallest moai erected, called Paro, was almost 10 metes (33 ft) high and weighed 75 tons; the heaviest erected was a shorter but squatter moai at Ahu Tongariki, weighing 86 tons; and one unfinished sculpture, if completed, would have been approximately 21 metres (69 ft) tall with a weight of about 270 tons.
Completed statues were moved to ahu mostly on the coast, then erected, sometimes with red stone cylinders (pukao) on their heads. Moai must have been extremely expensive to craft and transport; not only would the actual carving of each statue require effort and resources, but the finished product was then hauled to its final location and erected.
Easter Island, together with its closest neighbor, the tiny island of Isla Sala y Gómez 415 km further east, is recognized by ecologists as a distinct ecoregion, the Rapa Nui and and_Sala-y-Gomez_subtropical broadleaf forests. Over-exploitation and the scant rainfall contributed not only to eventual deforestation, but also to a broad ecological collapse. The original subtropical moist broadleaf forests have now disappeared, but paleobotanical studies of fossil pollen and tree moulds left by lava flows indicate that the island was formerly forested, with a range of trees, shrubs, ferns, and grasses.
A large palm, Paschalococos disperta, related to the Chilean wine palm (Jubaea chilensis), was one of the dominant trees, as was the toromiro tree (Sophora toromiro). The palm is now extinct, and the toromiro is extinct in the wild. However, the Royal Botanic Gardens, Kew, and the Göteborg Botanical Garden are jointly leading a scientific program to reintroduce the toromiro to Easter Island. The island is, and has been for at least the last three centuries, mainly covered in grassland with nga'atu or bulrush in the crater lakes of Rano Raraku and Rano Kau. Presence of these reeds, called totora in the Andes, was used to support the argument of a South American origin of the statue builders, but pollen analysis of lake sediments shows these reeds have grown on the island for over 30,000 years. Before the arrival of humans, Easter Island had vast seabird colonies, no longer found on the main island, and several species of landbirds, which have become extinct.
Destruction of the ecosystem
There have been a number of theories as to what destroyed the ecosystem of Easter Island, including the thriving human culture. Early theorists were baffled by the disappearance of a society powerful enough to create an army of Moai without modern tools. One of the first ideas held that an advanced South American population had inhabited the island and eventually left to be replaced by less advanced Polynesians. Wilder theories contended that extraterrestrials had something to do with Moai or that Easter Island was part of an archipelago that sunk into the sea like Atlantis. In recent years scientists have concentrated on deforestation leading to general disruption of the island's environment as the most likely scenario, although the precise mechanisms are debated.
Deforestation, among other ecological factors that decrease the likelihood of survival, was not only an issue on Easter Island, but may have been an active part of ecological deterioration on othe Pacific islands. The contrast between the east Polynesian Islands and the west Pacific archipelagos is striking enough to cause difficulties in adaptation and survival. Traditionally, there was a reliance on a shifting cultivation system in the western Pacific. In the east, the smaller islands have less rainfall, which makes shifting cultivation nearly impossible, as well as increases the likelihood of deforestation. Unfortunately for its inhabitants, Easter Island possessed other environmental factors that made deforestation more likely. Analysis of the eastern Pacific islands shows that low topography, low inputs of soil-enriching continental dust, and little or no volcanic ash fallout predispose small, dry islands to deforestation. Other islands struggling with these factors developed irrigated agriculture, and human populations survived by consuming such foods as breadfruit and the Tahitian chestnut, two of the most important Polynesian tree crops. Easter Island was plagued by the negative environmental conditions, as well as cursed by the impossibility of irrigation and the absence of vital crops all before it was colonized.
In his article "From Genocide to Ecocide: The Rape of Rapa Nui", Benny Peiser notes that when Europeans first arrived, that Easter Island may still have had some (small) trees, mainly toromiro, even though most primordial biodiversity had been lost. Cornelis Bouman, Jakob Roggeveen's captain, stated in his log book, "... of yams, bananas and small coconut palms we saw little and no other trees or crops." According to Carl Friedrich Behrens, Roggeveen's officer, "The natives presented palm branches as peace offerings. Their houses were set up on wooden stakes, daubed over with luting and covered with palm leaves,” presumably from banana plants as the island was by then deforested.
A more likely theory claims, alternatively, that it is probable that the Polynesians who settled on Easter Island brought about their own destruction through overpopulation and over-exploitation of resources. It was customary in western Pacific tradition to bring rats on exploratory expeditions, as a precautionary measure against a lack of immediate food wherever the settlers landed. This theory holds that, after arriving on Easter Island, the rat population exploded to over a million in merely a few years. This growth, coupled with the absence of indigenous rat predators on the island, meant that the vegetation on the island was severely vulnerable to rat predation. It is then thought that the rats effectively deforested the island by subsisting on the nuts, seeds, bark, seedlings, etc. of the plants, many of which yielded plentiful fruit and were not poisonous. A significant change in the structure of the pollen rain after the first arrival of humans, and therefore rats, but before the first indications of forest burning and soil erosion on an island is taken as proof that rats are known agents of extermination on many islands. Easter Island does not display such evidence, but it has been suggested that the environmental changes on the island happened too quickly to register in the relatively rough stratigraphic records available today.
James Brander and Scott Taylor used an economic analysis of Easter Island's resources to determine why society collapsed. Using economic systems developed by noted economists Thomas Malthus and David Ricardo, Brander and Taylor use predator/prey analogies for the resource depletion patterns in closed systems like Easter Island. Essentially, their findings rest on the fact that increases in resources spur increases in population, which feeds back into a need for more resources. Application of the model produces "boom and bust" cycles, where the population grows to the point of degrading necessary resources and ultimately breaks down. This process is facilitated by the rapid growth of population and the slow regeneration of the resource base.
In the wake of conflicting Easter Island theories, a host of scenarios attempt to describe the collapse of Easter Island's society. Disagreement stems from conflicting stories at the time of European contact and the difficulty in precisely studying century old events. However, there is consensus on the fact that Easter Island at one time had a thriving civilization, fertile soil, and an abundance of native vegetation. Even if Easter Island was predisposed to lose these resources, human activities cannot be overlooked as our modern society may face the same peril on a much larger scale. Instead of concentrating on one critical theory, a careful analysis would take input from all reasonable ideas. If Easter Island was predisposed to dry climate, an explosion in the rat population, coupled with a large human population, and non-sustainable resource harvesting techniques may very well have come together to tear society asunder.
References and further reading
- Brander, James, and Scott Taylor. "The Simple Economics of Easter Island: A Ricardo-Malthus Model of Renewable Resource Use." The American Economic Review 88(1998): 119-138.
- "History of Easter Island." Wikipedia, The Free Encyclopedia. 25 Sep 2008, 21:04 UTC. 15 Dec 2008.
- Mann, Daniel, james Edwards, Julie Chase, Warren Beck, Richard Reanier, Michele Mass, Bruce Finney and John Loret. "Drought, vegetation change, and human history on Rapa Nui (Isla de Pascua, Easter Island)." Quaternary Research 69(2008): 16-28.
- Rolett, Barry. "Avoiding collapse: Pre-European sustainability on Pacific Islands." Quarternary International 184(2008): 4-10.
- Zicus, Sandra. "Rapa Nui subtropical broadleaf forests." World Wildlife Fund 14 Dec 2008.