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Human responses to climate change in Australia over the past 2000 years

Williams, Ulm, Goodwin and Smith have just had a paper published in the Journal of Quaternary Science that explores broad patterns in human occupation and environmental change across Australia over the past 2,000 years. It’s worth a quick summary post here.

The paper presents:

an analysis of sum probability distributions of 1275 radiocarbon ages from 608 archaeological sites to explore the relationship between archaeological records and palaeoclimatic records across central and northern Australia

As they say, they use these radiocarbon data to model time series trends that highlight occupation patterns across Australia during the past 4,000 years. They link this to climate models which during this period are most strongly influenced by the El Niño Southern Osscillation (ENSO). The figure below, which I reproduce here from their paper (P 833), illustrates how these two datasets relate to each other.

In short, they identify two key trends at periods highlighted on this figure. First, that a period of increased La Niña activity at around AD 500 to 700 resulted in less variable, wetter conditions and this corresponded to a reduction in archaeological signatures. Second, increasingly variable conditions during a period of stronger El Niña activity (more variable, less rainfall) between AD 1150-1500 led to an increase in archaeological signatures.

They imply that reductions or increases in archaeological signatures are in a sense a proxy for the degree of mobility employed by Aboriginal hunter-gatherer populations in Australia. They suggest that the earlier trend is “hard to explain” (p 835) because a change toward more favourable (less variable, wetter) conditions could be expected to produce an increased archaeological signature due to more resources rather than the reduction in the signature that they document. They account for this possible discrepancy by arguing that “increasing sedentism or a shift to logistical mobility strategies”(p 835) may have resulted in this reduced signature. Another line of evidence, such as increased intensity of use of some sites might help to resolve this issue (e.g. Lourandos and David 1998).

The main thrust of their argument though relates to explaining the substantial evidence for increasingly variable conditions and an increased archaeological signature between about AD 1150 and 1500. They argue that increasing variability may have resulted in greater levels of resource stress for people who responded by adopting more mobile settlement patterns. In addition, they point out that at this time regional archaeological signatures from many parts of Australia evidence a range of economic, technological and demographic changes (new technologies, new resources being used, etc). Their view is that these changes can be best explained as adaptations to these increasingly variable conditions.

It’s a useful paper that encapsulates a re-emerging debate in Australia about human-environmental interactions over the past 4,000 years. They have tended to omit any discussion of the ‘s’ word (‘social’) however the value of this paper is in the quite wide ranging synthesis it presents, rather than how it engages with previous debates about late Holocene change in Australia. I’m not entirely convinced by their explanations of the trends since they lack explanation of just why and how people responded to increasing/decreasing environmental variability in these ways, but it raises some important new questions that archaeologists exploring issues in the archaeology of the Late Holocene in Australia need to address.

Their abstract can be found at the JQS website I seemed to be able to access it without institutional login, so hopefully it’s not behind a paywall.

Haberle, S. and B. David, 2004 Climates of change: human dimensions of Holocene environmental change in low latitudes of the PEPII transect Quaternary International 118-119: 165-179.

Williams, A. N. et al., 2010 Hunter-gatherer response to late Holocene climatic variability in northern and central Australia Journal of Quaternary Science 25 (6): 831-838. 

Lourandos, H. and B. David., 1998 Comparing long-term archaeological and environmental trends: north Queensland, arid and semi-arid Australia The Artefact 21: 105-14. 

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