Climate and Conflict in the Pacific

A threat being posed by climate to society is by no means a new phenomenon. In this entry I will focus upon a climate event known as the ‘A.D. 1300 Event’ and the effect that it had on inhabitants of islands throughout the Pacific.

The year 1300 A.D. marks the beginning of a period of transition lasting around 200 years between a time of warm dry conditions commonly referred to as the Medieval Warm Period (MWP) and a time of cooler conditions know as the Little Ice Age. This period while also largely dry saw a substantial yet short lived increase in precipitation in many areas across the Pacific. The transition from one stage to the other saw a temperature reduction of around 1.5^oC and a reduction in sea level by between 75 and 115cm.  It has been shown by Nunn (2000) that such a change in climate associated with this transition fundamentally changed societies across the islands of the Pacific.

It is put forward by Nunn (2000) that the 1.5^oC reduction in temperature will have led to a reduction in crop yields, particularly for those crops that before the transition were already living at the edge of their temperature tolerance, leading to a reduction in food availability. The productivity of marine ecosystems, especially those close to the shore line is also likely to have been reduced. An example of this is the reduction in pearl oysters in the Cook Islands to such an extent that they were no longer harvested after 550 cal yr BP, in addition there was as a change in fishing strategies implemented as fisherman had to sail further afield to catch fish (Nunn, 2003).

Sea level fall had similarly negative effects on marine ecosystems as the most productive parts of reefs emerged from the water. As these ecosystems were relied upon by the inhabitants of many Pacific islands for food, the reduction in resources led to the carrying capacity of islands being exceeded and thus the subsequent increase in competition resulted in conflict between different groups of humans (Nunn, 2003).

In Fiji there is evidence of the first construction of forts around 500-700 BP therefore supporting the idea that it was a change in climate that led to conflict with the islands society. A detailed study of the Lau group in eastern Fiji has shown that there was a change on the location of settlements from being located by the coast to more easily defensible hilltop locations.  The size of these hilltop settlements was also much less than that of coastal settlements. The move towards a large number of small fortified settlements has been explained by a rise in internal conflict that resulted due to a depletion of marine resources. There is also evidence of a similar event occurring on a small group of islands of Micronesia called Palau. Nunn (2000) explains that in this area a catastrophic climate event around 1200AD destroyed the islands’ resource base and thus caused conflict which resulted in the areas inhabitants moving from the three large high islands that comprise Palau to more easily defended offshore rock islands.

The conflict that occurred in the pacific led to the settlement of a number of newly habitable areas. As mentioned in the previous post sea level reduction led to the emergence of new reef islands that could then be settled. In addition, sea level reduction led to a fall in the water table of many islands and therefore previously swampy areas dried out and became habitable. An example of this is the Lelcei valley of Aneityum island, Vanuatu, which was first occupied around 642 cal yr BP.

Another facet of society that was affected by the climate transition was voyaging which was brought to its end. During the MWP humans in the Pacific undertook long distance voyages as evidenced by the settling of Easter Island and New Zealand.  However archaeological and oral-historical evidence shows that during the LIA contact between islands was suddenly and greatly reduced. It has been posited that this occurred due to an increase in precipitation and storminess as well as due to a loss of cultural will to undertake such journeys

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Overall it can be seen that the change in climate that occurred around 1300 A.D. had a hugely significant impact on societies located in the Pacific. Most notable is the cultural transformation from a peaceful society where large populations lived in coastal settlements to a society where conflict was rife. As such people moved from settlements in the coastal areas of large islands to settlements located on more easily defendable, more dispersed and smaller islands. A complete model of the effects of this event can be seen in figure 1. 

Figure 1:  A model of the A.D '1300 event' (Source).