Chapter 12
The Context of Global Climate Change:
Climate-Driven Demography
Abstract The demographic assumption of late settlement theorists is of a population rapidly increasing over 200 years from AD 1200 to AD 1400, during the warm
global climate period (the Medieval Climatic Optimum) and then, in contradiction
to global patterns, continuing to increase at the same rate during the Little Ice Age.
A continuous population increase might be arguable if there were no evidence of
food scarcity and of associated conflict over land and resources after 1400 due to
the global cold conditions of the Little Ice Age. The 7,000 pa (hill-forts) built during this period and the extreme population decline rates derived from an analysis
of skeletal data in Chapter 14 both contradict this assumption. The conclusion that
follows is that population levels in New Zealand were high enough at the beginning of the Little Ice Age for ceilings of sustainability to be breached when adverse
climatic conditions reduced the biota. Given the large landmass of New Zealand,
population levels would have to have been very considerable for this to have happened. High populations by AD 1400 imply significant time depth for settlement
in New Zealand, given that till AD 1200 New Zealand would have had a population growth rate consistent with a settled hunter/gatherer population, rather than one
appropriate for a horticulturally based society.
Keywords Climate-driven demography · Medieval Climatic Optimum · Little Ice
Age · Global climate change · Erosion · New Zealand · Population ceilings
12.1 Introduction
Considerable advances have been made in the last two decades in climate research,
most notably in the understanding of ENSO (El Nino Southern Oscillation events).
The severe El Niño events of 1982–1983 and 1997–1998 triggered deep general
concerns about the possible consequences of global warming and brought new
interest in climate history. Hoping to predict future climate patterns, researchers
have turned to the past for data and for insights from past patterns of climate
change. Though published in 1972, the classic book on climate history, H.H. Lamb’s
193
C.E.M. Pearce, F.M. Pearce, Oceanic Migration,
DOI 10.1007/978-90-481-3826-5_12, C
Springer Science+Business Media B.V. 2010
The Context of Global Climate Change:
Climate-Driven Demography
Abstract The demographic assumption of late settlement theorists is of a population rapidly increasing over 200 years from AD 1200 to AD 1400, during the warm
global climate period (the Medieval Climatic Optimum) and then, in contradiction
to global patterns, continuing to increase at the same rate during the Little Ice Age.
A continuous population increase might be arguable if there were no evidence of
food scarcity and of associated conflict over land and resources after 1400 due to
the global cold conditions of the Little Ice Age. The 7,000 pa (hill-forts) built during this period and the extreme population decline rates derived from an analysis
of skeletal data in Chapter 14 both contradict this assumption. The conclusion that
follows is that population levels in New Zealand were high enough at the beginning of the Little Ice Age for ceilings of sustainability to be breached when adverse
climatic conditions reduced the biota. Given the large landmass of New Zealand,
population levels would have to have been very considerable for this to have happened. High populations by AD 1400 imply significant time depth for settlement
in New Zealand, given that till AD 1200 New Zealand would have had a population growth rate consistent with a settled hunter/gatherer population, rather than one
appropriate for a horticulturally based society.
Keywords Climate-driven demography · Medieval Climatic Optimum · Little Ice
Age · Global climate change · Erosion · New Zealand · Population ceilings
12.1 Introduction
Considerable advances have been made in the last two decades in climate research,
most notably in the understanding of ENSO (El Nino Southern Oscillation events).
The severe El Niño events of 1982–1983 and 1997–1998 triggered deep general
concerns about the possible consequences of global warming and brought new
interest in climate history. Hoping to predict future climate patterns, researchers
have turned to the past for data and for insights from past patterns of climate
change. Though published in 1972, the classic book on climate history, H.H. Lamb’s
193
C.E.M. Pearce, F.M. Pearce, Oceanic Migration,
DOI 10.1007/978-90-481-3826-5_12, C
Springer Science+Business Media B.V. 2010