204
12 The Context of Global Climate Change: Climate-Driven Demography
amongst the earliest inhabited sites in New Zealand, so that the finding of tools there
14 ft below the surface is not surprising.
12.7 The Medieval Climatic Optimum in New Zealand
Grant’s description makes clear the risk of starvation to Maori populations dependent on forest, marine and estuarine resources, once population levels were high and
resources, scarcely adequate, were suddenly reduced by floods and forest destruction. Given our premise of a very early first settlement, it is likely that populations
were high enough by AD 1180, the beginning of the Warm Waihirere Period, and
similarly by AD 1510, the beginning of the Early Matawhero Period, for there to be
some population decline in both these adverse climate periods. It seems likely that
in the less well-resourced areas populations would be especially vulnerable and that
to some extent at least this vulnerability must have affected all areas.
We can, however, expect a significant difference after about AD 1200, when the
kumara, taro, yam and gourd were introduced to some areas of New Zealand, areas
some of which were later to become major pa areas. The large-scale establishment
of horticulture can probably be attributed to the favourable warmth of the Medieval
Climatic Optimum. Good harvests could be expected then and would have been a
buffer against starvation. We think it likely that populations in horticultural areas,
which in the warmer Medieval Climatic Optimum may have included areas in the
south of the North Island, were largely protected from the population decline suffered in the non-horticultural areas during the Warm Waihirere Period. The major
horticultural areas included Taranaki, the Bay of Plenty, the Bay of Islands, the
Auckland Isthmus and the northwest coast of the North Island, which were able to
exploit rich alluvial and volcanic soils to grow the newly introduced tropical cultivars and especially kumara. Rich not only in good soils but in marine and estuarine
resources, these areas in some cases had added resources from lakes and rivers and
good harbours giving access to offshore fishing. Indeed, these optimal areas may
always have supported the largest populations in New Zealand. Probably many of
the earliest settlements in the North Island were located in these resource-rich areas.
The alluvial soils that allowed a thriving horticulture to be established in these areas
in the Medieval Climatic Optimum, however, are evidence of the vulnerability of
these areas to erosion. They offer testimony to the likely deep burial of evidence for
earlier settlements in these choice locations.
12.8 The Little Ice Age in New Zealand
Assuming an early first settlement and significant populations by the beginning of
the Little Ice Age, conditions would probably have deteriorated in the Little Ice Age
even in the favoured areas. For cold would have reduced kumara harvests drastically.
Though adapting the kumara, which was a perennial in tropical Polynesia, through
skilful horticultural practice, to function as an annual in New Zealand, would have
12 The Context of Global Climate Change: Climate-Driven Demography
amongst the earliest inhabited sites in New Zealand, so that the finding of tools there
14 ft below the surface is not surprising.
12.7 The Medieval Climatic Optimum in New Zealand
Grant’s description makes clear the risk of starvation to Maori populations dependent on forest, marine and estuarine resources, once population levels were high and
resources, scarcely adequate, were suddenly reduced by floods and forest destruction. Given our premise of a very early first settlement, it is likely that populations
were high enough by AD 1180, the beginning of the Warm Waihirere Period, and
similarly by AD 1510, the beginning of the Early Matawhero Period, for there to be
some population decline in both these adverse climate periods. It seems likely that
in the less well-resourced areas populations would be especially vulnerable and that
to some extent at least this vulnerability must have affected all areas.
We can, however, expect a significant difference after about AD 1200, when the
kumara, taro, yam and gourd were introduced to some areas of New Zealand, areas
some of which were later to become major pa areas. The large-scale establishment
of horticulture can probably be attributed to the favourable warmth of the Medieval
Climatic Optimum. Good harvests could be expected then and would have been a
buffer against starvation. We think it likely that populations in horticultural areas,
which in the warmer Medieval Climatic Optimum may have included areas in the
south of the North Island, were largely protected from the population decline suffered in the non-horticultural areas during the Warm Waihirere Period. The major
horticultural areas included Taranaki, the Bay of Plenty, the Bay of Islands, the
Auckland Isthmus and the northwest coast of the North Island, which were able to
exploit rich alluvial and volcanic soils to grow the newly introduced tropical cultivars and especially kumara. Rich not only in good soils but in marine and estuarine
resources, these areas in some cases had added resources from lakes and rivers and
good harbours giving access to offshore fishing. Indeed, these optimal areas may
always have supported the largest populations in New Zealand. Probably many of
the earliest settlements in the North Island were located in these resource-rich areas.
The alluvial soils that allowed a thriving horticulture to be established in these areas
in the Medieval Climatic Optimum, however, are evidence of the vulnerability of
these areas to erosion. They offer testimony to the likely deep burial of evidence for
earlier settlements in these choice locations.
12.8 The Little Ice Age in New Zealand
Assuming an early first settlement and significant populations by the beginning of
the Little Ice Age, conditions would probably have deteriorated in the Little Ice Age
even in the favoured areas. For cold would have reduced kumara harvests drastically.
Though adapting the kumara, which was a perennial in tropical Polynesia, through
skilful horticultural practice, to function as an annual in New Zealand, would have