 |
| Figure 1. The famous statues of Easter Islands (source) |
Rapa Nui (Easter Island) is a one of the most remote islands in the world. It is a small volcanic island of 164 km2, low relief, and low rainfall. It is another classic example of a complex societal collapse which is proving to be one of the most important examples with regards to holding lessons for the future. As reported by Hunt (2007), when and how the first humans discovered Rapa Nui is still highly debated. Today, cultural evidence continue to dominate the landscape as huge sculptures were erected throughout the island between AD 1200 and AD 1650. At peak, the population may have reached 10,000, yet in AD 1650, this dramatically reduced as the civilization headed for collapse. Important lessons could be learnt from this societal collapse story with regards to the future therefore this blog will explore the main drivers behind the collapse with special reference to the role of climate change.
A classic view of the Easter Island collapse story is one of 'ecocide' as the human population drove its own destruction by exploiting its natural resources, degrading the island's lands, causing extensive deforestation, and driving the extinction of plants and animals (Diamond, 2005). Extensive deforestation has received considerable attention, as this would have prevented the society from building boats and rafts to escape from ecosystem damage. Diamond writes that ‘‘in just a few centuries, 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.’’.
This has been heavily criticised as presenting an environmental deterministic view. There exists no reliable evidence of a large population which could not sustain itself followed by an abrupt, cataclysmic collapse (Hunt., 2007) and Rapa Nui does not appear to represent a case of ‘‘ecocide.’’. Instead, the arrival of Europeans to the island, bringing with the new species, diseases and slave-trading has been suggested to play a more crucial role (Peiser, 2005). It has been reported that the societal collapse on Easter Island is ‘‘one of the most hideous atrocities committed by white men in the South Seas" (Metraux,1957).
Other theories suggest that the arrival of the European bought rapidly reproducing rats to the islands, and that this invasive caused considerable damage to plants and animals, dramatically changing the islands food chain and resources and driving the society towards collapse (Hunt, 2007). This theory has been heavily critisiced on the basis that the rats could not have reproduced fast enough to cause such devastating consequences (Mann et al., 2008).
 |
| Figure 2: An identified period of intense deforestation which coincides with an El Nino-Southern Oscillation period (source) |
A studies which used pollen to reconstruct vegetation chance across the island found a correlation between a period of major deforestation and an intense El Nino-Southern Oscillation period (figure 2, Cobb et al. 2003). ENSO events result in a change in sea surface temperature, which leads to the lowering of biomass production and upwhelling of nutrients. This would have reduced the availability of marine resources around the island, a key source of protein for the islanders. An abrupt ENSO event could have caused a significant decline in food resources, driving an expansion in agriculture, and reducing the availability of wood to make boats would have also made fishing ground inaccessible. The role of climate change has a more recently been confirmed by a more recent study which identified period of drought being experienced on the island prior to the collapse of the civilization at AD1180-1290 (Mann et al. 2008). Stratigraphic records from lake sediment cores looking at sediment, charcoal and pollen stratigraphy suggests that the lake dried out during this period of drought identified by a hiatus in sedimentation. The study concludes that it looks likely that latitudinal shifts of tropical storm tracks, changed to the moisture balance across the island triggered the period of drought.
As we have previously explore in many past blogs, the relationship between civilisations and the climate is highly complex! Both interlink with each other. Hence, when attempting to understand what caused past civilisations to collapse, it is difficult to isolate individual signals from the records and pin pointing a specific climatic change or societal driver. However, many key lessons can be learnt from past societies including the need to be aware of the damage that we are causing to the planet, the need to plan and prepare with adequate mitigation measures, and the need to be flexible and adaptable to change. Only then can we survive this world's dynamic climate.