240
14 New Zealand Palaeodemography
Patrick Grant’s analysis of the effects of the “warm wet erosion periods” that
took place during the Medieval Climate Optimum, and of the two brief erosion periods that occurred during the Little Ice Age, helps to explain the long period over
which, the skeletal evidence implies, population decline may have occurred in New
Zealand. Grant’s study of the effects of adverse climate on New Zealand’s landscape
and ecology shows that considerable fluctuations occurred in the severity of both the
extreme warmth and extreme cold that mark the Medieval Climatic Optimum and
the Little Ice Age in New Zealand. But both singly and cumulatively through their
juxtaposition, severe conditions during these two climate periods in different ways
had devastating effects on the ecology of New Zealand and on humans and other
species included in that ecology. In the Medieval Climatic Optimum, as we have
seen, the damage to the ecology was from erosion and gales which destroyed forests,
coasts and estuaries and clogged rivers and lakes and from forest destruction associated with the introduction of horticulture. In the Little Ice Age there was a more
direct reduction of biota at all levels through extreme cold. Populations which had
already reached the limit of available resources in their tribal areas, by the beginning
of or during the Medieval Climatic Optimum, would have been faced with starvation
when the biota was reduced either by erosion or cold.
Given that much of the skeletal material that Brewis, Molloy and Sutton used in
their analysis may have originated outside the best resourced, most densely populated pa areas, such as Taranaki, the Auckland Isthmus, the Bay of Plenty, the Bay
of Islands and the west coast of the north of the North Island, it is possible that the
long period of population decline established from the skeletal analysis may fully
apply only outside the better resourced pa areas. It is likely that in areas with lower
resource ceilings, and most especially the south of the North island, our recalculated
parameters for the skeletal data accurately chart the scale of this decline. But in the
areas with the best natural resources, especially after the successful introduction of
horticulture, populations helped by the favourable warmth of the Medieval Climatic
Optimum may have been better protected from starvation. The successful introduction of horticulture in favoured areas (and in the Medieval Climatic Optimum these
may have included the south of the North Island) may have buffered inhabitants
from a resource crisis that might otherwise have occurred in the Medieval Climatic
Optimum following ecological damage to the biota.
In the Little Ice Age, as we argued in Chapter 12, the situation would, however, have been very different even in the north of the North Island. Cold would
have reduced kumara harvests drastically. In the warm conditions of the Medieval
Climatic Optimum, the tropical cultivars introduced into New Zealand would not
have become cold-adapted. A simultaneous reduction in horticultural harvests and
in the areas where they could be successfully grown, reductions in forest biota,
shellfish and fish stocks, following on the heels of earlier reductions of biota during
the Warm Waihirere erosion period, we have suggested, may have brought starvation to these richer areas for the first time. Even more obviously they may have
brought starvation to areas where in the Little Ice Age tropical cultivars could
no longer be grown. In the south of the North Island especially there may have
been large populations which had been supported by horticulture in the Medieval
14 New Zealand Palaeodemography
Patrick Grant’s analysis of the effects of the “warm wet erosion periods” that
took place during the Medieval Climate Optimum, and of the two brief erosion periods that occurred during the Little Ice Age, helps to explain the long period over
which, the skeletal evidence implies, population decline may have occurred in New
Zealand. Grant’s study of the effects of adverse climate on New Zealand’s landscape
and ecology shows that considerable fluctuations occurred in the severity of both the
extreme warmth and extreme cold that mark the Medieval Climatic Optimum and
the Little Ice Age in New Zealand. But both singly and cumulatively through their
juxtaposition, severe conditions during these two climate periods in different ways
had devastating effects on the ecology of New Zealand and on humans and other
species included in that ecology. In the Medieval Climatic Optimum, as we have
seen, the damage to the ecology was from erosion and gales which destroyed forests,
coasts and estuaries and clogged rivers and lakes and from forest destruction associated with the introduction of horticulture. In the Little Ice Age there was a more
direct reduction of biota at all levels through extreme cold. Populations which had
already reached the limit of available resources in their tribal areas, by the beginning
of or during the Medieval Climatic Optimum, would have been faced with starvation
when the biota was reduced either by erosion or cold.
Given that much of the skeletal material that Brewis, Molloy and Sutton used in
their analysis may have originated outside the best resourced, most densely populated pa areas, such as Taranaki, the Auckland Isthmus, the Bay of Plenty, the Bay
of Islands and the west coast of the north of the North Island, it is possible that the
long period of population decline established from the skeletal analysis may fully
apply only outside the better resourced pa areas. It is likely that in areas with lower
resource ceilings, and most especially the south of the North island, our recalculated
parameters for the skeletal data accurately chart the scale of this decline. But in the
areas with the best natural resources, especially after the successful introduction of
horticulture, populations helped by the favourable warmth of the Medieval Climatic
Optimum may have been better protected from starvation. The successful introduction of horticulture in favoured areas (and in the Medieval Climatic Optimum these
may have included the south of the North Island) may have buffered inhabitants
from a resource crisis that might otherwise have occurred in the Medieval Climatic
Optimum following ecological damage to the biota.
In the Little Ice Age, as we argued in Chapter 12, the situation would, however, have been very different even in the north of the North Island. Cold would
have reduced kumara harvests drastically. In the warm conditions of the Medieval
Climatic Optimum, the tropical cultivars introduced into New Zealand would not
have become cold-adapted. A simultaneous reduction in horticultural harvests and
in the areas where they could be successfully grown, reductions in forest biota,
shellfish and fish stocks, following on the heels of earlier reductions of biota during
the Warm Waihirere erosion period, we have suggested, may have brought starvation to these richer areas for the first time. Even more obviously they may have
brought starvation to areas where in the Little Ice Age tropical cultivars could
no longer be grown. In the south of the North Island especially there may have
been large populations which had been supported by horticulture in the Medieval