200
12 The Context of Global Climate Change: Climate-Driven Demography
To establish their claims the authors focus on the effects of these droughts in the
Great Basin and Sierra Nevada, the southern Californian coast, the Mojave Desert
and the Colorado Plateau (p. 142), providing detailed discussion of the cultural and
demographic consequences of “epic droughts” in all four regions. They argue that
archaeological sequences from the four regions show
striking correlations between changes in subsistence, interregional exchange, frequency of
warfare and interpersonal violence, regional abandonments, and major population movements, on the one hand, and events in the paleoenvironmental record, on the other. Specific
cultural responses vary between regions, but each shows diachronic changes that are difficult to attribute to simple adaptive adjustments or economic intensification. Rather, events
in each of these regions are best explained as responses to environmental deterioration and
demographic stress (p. 145).
The authors show the same patterns affecting agricultural and hunter-gatherer
regions and document responses to demographic stress in both in some detail. In
northern Colorado, for example, they note
Agricultural settlements across much of the northern Colorado Plateau were abandoned during a subsequent epic drought between 1130 and 1150, while populations aggregated to the
south and east. Nucleation was ultimately curtailed during the Great Drought with the final
collapse of settlements across most of the central Colorado Plateau. Centuries of population
growth limited the subsistence options that were formerly available to dispersed farming
groups, and during the later droughts many Pueblan populations were beyond a carrying
capacity that had declined as a result of extended drought. Throughout the late medieval
period there is mounting evidence for intergroup warfare and interpersonal violence in this
context of food stress (p. 155).
For both agriculturalists and hunter/gatherers they conclude that “Situations in
the case studies considered here are best explained in terms of a convergence
of rapidly growing human populations and precipitous declines in environmental
productivity” (p. 156).
The examples we have quoted from Europe, tropical Polynesia and North
America of global climate extremes impacting in different ways and in different
eras on populations which had reached or breached their levels of sustainability
provide a context in which we can now examine the climate-driven palaeodemography of New Zealand . These examples illustrate the fact that whether it is drought
or cold that impacts on a biosystem and drastically reduces food availability, demographic consequences will vary according to the margins for sustainability to be
found among affected populations. These margins will vary not only from country to country but from region to region within a country. In the same period of
resource depletion, people in the poorer Scottish highlands will suffer more rapidly
and extremely than those living in the more fertile areas of Surrey. All faced with
climate-driven famine will be forced to seek adaptive means for improving their
chances of survival. Some hunter/gatherers may adopt horticulture at least temporarily; others may raid horticulturalists’ harvests. Where opportunities for migration
are limited, conflict over land and resources is inevitable: for each tribe or group
success in seizing or maintaining control of land and resources will ultimately determine demographic outcomes. Thus the sudden proliferation in pa-building in New
12 The Context of Global Climate Change: Climate-Driven Demography
To establish their claims the authors focus on the effects of these droughts in the
Great Basin and Sierra Nevada, the southern Californian coast, the Mojave Desert
and the Colorado Plateau (p. 142), providing detailed discussion of the cultural and
demographic consequences of “epic droughts” in all four regions. They argue that
archaeological sequences from the four regions show
striking correlations between changes in subsistence, interregional exchange, frequency of
warfare and interpersonal violence, regional abandonments, and major population movements, on the one hand, and events in the paleoenvironmental record, on the other. Specific
cultural responses vary between regions, but each shows diachronic changes that are difficult to attribute to simple adaptive adjustments or economic intensification. Rather, events
in each of these regions are best explained as responses to environmental deterioration and
demographic stress (p. 145).
The authors show the same patterns affecting agricultural and hunter-gatherer
regions and document responses to demographic stress in both in some detail. In
northern Colorado, for example, they note
Agricultural settlements across much of the northern Colorado Plateau were abandoned during a subsequent epic drought between 1130 and 1150, while populations aggregated to the
south and east. Nucleation was ultimately curtailed during the Great Drought with the final
collapse of settlements across most of the central Colorado Plateau. Centuries of population
growth limited the subsistence options that were formerly available to dispersed farming
groups, and during the later droughts many Pueblan populations were beyond a carrying
capacity that had declined as a result of extended drought. Throughout the late medieval
period there is mounting evidence for intergroup warfare and interpersonal violence in this
context of food stress (p. 155).
For both agriculturalists and hunter/gatherers they conclude that “Situations in
the case studies considered here are best explained in terms of a convergence
of rapidly growing human populations and precipitous declines in environmental
productivity” (p. 156).
The examples we have quoted from Europe, tropical Polynesia and North
America of global climate extremes impacting in different ways and in different
eras on populations which had reached or breached their levels of sustainability
provide a context in which we can now examine the climate-driven palaeodemography of New Zealand . These examples illustrate the fact that whether it is drought
or cold that impacts on a biosystem and drastically reduces food availability, demographic consequences will vary according to the margins for sustainability to be
found among affected populations. These margins will vary not only from country to country but from region to region within a country. In the same period of
resource depletion, people in the poorer Scottish highlands will suffer more rapidly
and extremely than those living in the more fertile areas of Surrey. All faced with
climate-driven famine will be forced to seek adaptive means for improving their
chances of survival. Some hunter/gatherers may adopt horticulture at least temporarily; others may raid horticulturalists’ harvests. Where opportunities for migration
are limited, conflict over land and resources is inevitable: for each tribe or group
success in seizing or maintaining control of land and resources will ultimately determine demographic outcomes. Thus the sudden proliferation in pa-building in New