Burn baby burn

In a 2008 study, Mann et al use macrofossils and pollen data from 2 sediment cores to investigate drought, vegetation changes and human settlement on Easter Island.

Interestingly they assert that they found no evidence of a rat outbreak that could have caused collapse. As a rat outbreak would affect tree abundances and species composition, any such event would be reflected in the pollen record. However no evidence was found. However they do point out that the paleo record of Easter Island is still very poorly understood and the stratigraphic record may be too coarse to reflect this event. Therefore if a higher resolution record can be obtained, it may be possible to accredit or disprove Hunt (2006)’s rat hypothesis.

Source: SkyMe

From their sediment cores, they are able to infer ecological changes and drought events that occurred on Easter Island. They found that the beginning of agriculture on the island occurred straight after a severe drought. Marked soil erosion was found to have occurred at 1200AD which they attribute to human deforestation.

They also investigate the role of fire on the island. Before human settlement, there is little evidence of fire in the stratigraphic record (i.e. very little charcoal in the record). This shows that natural fire on the island is very uncommon and resultantly the ecosystem is ‘fire-naïve’ or in other words is not used to fire, has a low tolerance and cannot recover well from fire events. After human settlement, human induced fire shown by increased charcoal in the sediment record provides evidence to suggest that human degradation of the environment was a primary cause in societal collapse.

What Easter Island may have looked like pre-human settlement. 

Source: Science-history-lover

But, it is very difficult to determine environmental changes on Easter Island. As Mann et al point out, the remoteness and isolation of the island makes it difficult to compare environmental changes with surrounding areas, as the nearest land is very far away and quite probably has a different environmental regime. However some links can be drawn. Mann et al explain that there is evidence of correlative drought events in central Chile that agree with the climate record on Easter Island. Therefore they suggest that central Chile may provide a comparison site and might demonstrate synchronous drought events. Rainfall changes in Chile and tree ring events from Patagonia and Tasmania correlate with a known drought event on Easter Island between 900-1100AD. Perhaps with a better understanding of the Easter Island paleo record we might be able to infer more from climate events in Chile and Patagonia.

However this evidence has since been developed by Mulrooney, 2013 who points out that we must not confuse correlation with causation: deforestation may not have caused societal collapse. The radiocarbon dates of this study contradict other studies that claim the island underwent widespread abandonment. Mulrooney found that inland areas were not abandoned as previously thought and the Rapa Nui utilized most of the island up until European colonization in the late 1600s. Similarly the archaeological evidence from the island does not fit a societal collapse scenario model. Radiocarbon dates show continued habitation of island throughout the previously assumed collapse period. 

Till next time!