198
12 The Context of Global Climate Change: Climate-Driven Demography
12.3 The Medieval Climatic Optimum in Tropical Polynesia
How relevant the climate-driven demographic patterns of Europe during the
Medieval Climatic Optimum and Little Ice Age are to New Zealand, we shall discuss shortly. First, it is useful to consider their relevance to tropical Polynesia. It
was not so much during the Little Ice Age that the tropical Polynesian islands suffered but during the preceding warm period. During this period El Niño-driven
drought and famine triggered warfare over land and resources within islands and
archipelagoes. Drought and famine prompted migrations and also effectively led to
invasions, as seen, for example, in the southern incursions into Hawaii in about AD
1100 from Samoa, Tahiti and the Marquesas. Southerners effectively took control of
the Hawaiian Islands, replacing indigenous chiefs and priests with their own. These
southern incursions had a lasting cultural impact even after Hawaii’s isolation was
restored when voyaging conditions deteriorated at the end of the Medieval Climatic
Optimum (in Hawaii, following northern hemisphere patterns, in AD 1250–1300).
The pattern of warfare, invasions and enforced migrations that we see operating
in tropical Polynesia in the Medieval Climatic Optimum occurred 300 years earlier
than in New Zealand. In tropical Polynesia recurrent El Niño-driven drought, not
cold, was the climatic factor that impacted on populations which had reached their
ceilings of sustainability probably by about AD 900 (see Chapter 19).
The increasing numbers of migration canoes reaching New Zealand during the
Medieval Climatic Optimum, probably carrying the starving and the defeated in
effectively enforced migrations, bear witness to the worsening of conditions in tropical Polynesia, as well as to optimal voyaging conditions to New Zealand. Perhaps
at no time since the period before 1000 BC that saw the Lapita migrations into the
Pacific were voyaging conditions to New Zealand better than during the Medieval
Climatic Optimum. Safer migration to New Zealand, combined with overpopulation, starvation and defeat in warfare in the tropics, would have provided greater
incentives for migrating to a distant New Zealand than for migration within Eastern
Polynesia, much of which may have been severely drought-affected. Very considerable population losses in tropical Polynesia in this period seem likely and may
have continued into the Little Ice Age if populations still outstripped resources. The
response of the Hawaiians to the arrival of Captain Cook’s ships, recorded in the
diary of the second-in-command, James King, suggests that this could have been so
[9]. King writes that the Hawaiians
imagined we came from some country where provisions had failed; and that our visit to
them was merely for the purpose of filling our bellies. Indeed, the meagre appearance of
some of our crew, the hearty appetites with which we sat down to their fresh provisions, and
our great anxiety to purchase, and carry off, as much as we were able, led them, naturally
enough, to such a conclusion.
Ross Couper-Johnston [10] quotes an even stronger record of starvation in the
story of the last king of Niue:
The body of the last recorded Patuiki or king of Niue, a French Polynesian island with
no natural supply of surface water, was discovered in the forest during a great famine.
His death, which probably dates to the exceptionally strong 1790–93 El Niño, is still
12 The Context of Global Climate Change: Climate-Driven Demography
12.3 The Medieval Climatic Optimum in Tropical Polynesia
How relevant the climate-driven demographic patterns of Europe during the
Medieval Climatic Optimum and Little Ice Age are to New Zealand, we shall discuss shortly. First, it is useful to consider their relevance to tropical Polynesia. It
was not so much during the Little Ice Age that the tropical Polynesian islands suffered but during the preceding warm period. During this period El Niño-driven
drought and famine triggered warfare over land and resources within islands and
archipelagoes. Drought and famine prompted migrations and also effectively led to
invasions, as seen, for example, in the southern incursions into Hawaii in about AD
1100 from Samoa, Tahiti and the Marquesas. Southerners effectively took control of
the Hawaiian Islands, replacing indigenous chiefs and priests with their own. These
southern incursions had a lasting cultural impact even after Hawaii’s isolation was
restored when voyaging conditions deteriorated at the end of the Medieval Climatic
Optimum (in Hawaii, following northern hemisphere patterns, in AD 1250–1300).
The pattern of warfare, invasions and enforced migrations that we see operating
in tropical Polynesia in the Medieval Climatic Optimum occurred 300 years earlier
than in New Zealand. In tropical Polynesia recurrent El Niño-driven drought, not
cold, was the climatic factor that impacted on populations which had reached their
ceilings of sustainability probably by about AD 900 (see Chapter 19).
The increasing numbers of migration canoes reaching New Zealand during the
Medieval Climatic Optimum, probably carrying the starving and the defeated in
effectively enforced migrations, bear witness to the worsening of conditions in tropical Polynesia, as well as to optimal voyaging conditions to New Zealand. Perhaps
at no time since the period before 1000 BC that saw the Lapita migrations into the
Pacific were voyaging conditions to New Zealand better than during the Medieval
Climatic Optimum. Safer migration to New Zealand, combined with overpopulation, starvation and defeat in warfare in the tropics, would have provided greater
incentives for migrating to a distant New Zealand than for migration within Eastern
Polynesia, much of which may have been severely drought-affected. Very considerable population losses in tropical Polynesia in this period seem likely and may
have continued into the Little Ice Age if populations still outstripped resources. The
response of the Hawaiians to the arrival of Captain Cook’s ships, recorded in the
diary of the second-in-command, James King, suggests that this could have been so
[9]. King writes that the Hawaiians
imagined we came from some country where provisions had failed; and that our visit to
them was merely for the purpose of filling our bellies. Indeed, the meagre appearance of
some of our crew, the hearty appetites with which we sat down to their fresh provisions, and
our great anxiety to purchase, and carry off, as much as we were able, led them, naturally
enough, to such a conclusion.
Ross Couper-Johnston [10] quotes an even stronger record of starvation in the
story of the last king of Niue:
The body of the last recorded Patuiki or king of Niue, a French Polynesian island with
no natural supply of surface water, was discovered in the forest during a great famine.
His death, which probably dates to the exceptionally strong 1790–93 El Niño, is still