Good and bad causes (and a new paper)

I’ve heard it said the the road to Hell is paved with false dichotomies, and this appears to be particularly true of academic theories about causality, a subject on which I was invited to speak at a workshop in Copenhagen about this time last year. The workshop also resulted in a special issue of the Danish Journal of Geography, which has just come out, and in which I have a paper.

Specifically, the workshop addressed causality in human-environment interactions, wrestling with the question of whether we can say a particular environmental change or stress can be said to “cause” a particular societal outcome.

Plymouth

Environmental change is just one factor that influences people’s decisions to migrate, but sometimes it can be the dominant factor. Photo: building buried by ash and pyroclastic flow in Plymouth, Montserrat. The town is now abandoned.

To anyone who has lost their house in a hurricane, or seen their crops wither and die in a drought, this question might seem ridiculous or even offensive. However, those who study human-environment interactions will point out that, somewhere along the line, a decision has been made to build a house in an area exposed to hurricanes, or to grow crops in a region prone to drought. It is the interaction between the vulnerability of human activities and infrastructure resulting from such decisions (to exploit or inhabit risky areas), and the occurrence of an environmental hazard or stress that results in risk, and in negative societal outcomes. In other words, environmental hazards only affect human activities or infrastructure that we put in their way.

The problem becomes more complex when we’re talking about the role of environmental stresses in larger-scale phenomena such as migration or the collapse of human societies. Droughts may act as triggers for food crises, but droughts of similar magnitude and duration can have very different societal impacts depending on the vulnerability of the exposed population. This is apparent in regions that have experienced meteorologically similar droughts in different years, with very different outcomes due to changes in government policies or the introduction of effective early warning and response systems. Can a drought be said to have caused a famine in one year, when a similar drought some years later leaves the same country or region relatively unscathed? It is widely accepted today that famines are as much man-made as they are natural disasters, even where drought acts as a trigger.

When it comes to climate change, the debate still rages on. Using terminology from the migration literature, on the one hand are what we might call the ‘maximalists’, who argue that climate change will ’cause’ migration and conflict, among other things. On the other are the ‘minimalists’, who maintain that climatic and environmental change represents just one set of factors among many that influence societal outcomes. Minimalists often go so far as to say that there is no point trying to separate environmental factors from other drivers of societal change, because of the multiplicity of factors contributing to these changes and the complexity of their interactions. The minimalist position seems to be gaining the upper hand, largely because of flaws in maximalist attempts to quantify the numbers of people who might be displaced, killed or otherwise affected by climate change.

Despite these flaws in maximalist thinking, there is a danger here that the triumph of minimalism will lead to a kind of nihilism, which will discourage people from examining the wider societal impacts of climate change. It may undermine attempts to quantify climate change damages, an approach that could be deployed to hold polluters to account and thus drive the large-scale behavioural changes that are required to tackle climate change effectively. And there is a further problem.

While the minimalist camp has evidence and subtlety on its side, it tends to ignore the fact that our empirical understanding of environmental drivers of phenomena such as migration is based on a very limited time window, namely the past few decades. The recent historical period is a poor guide to understanding how people react to massive, severe, and sustained changes in climatic and environmental conditions, as such changes have been few and far between in recent decades and even centuries (while there have been plenty of climatic and environmental shocks, the basic configuration of the global climate has remained essentially unchanged for millennia). Put simply, we don’t have any decent historical analogues for what’s coming, as the global climate reorganises itself over the coming decades (and centuries) in ways that we are struggling to anticipate. Somehow we need to extend the evidence base so that we have examples of how populations – and indeed societies at large – respond to such huge changes in climatic and environmental conditions.

In my paper from the Copenhagen workshop, I suggest that we might learn from the last period of global climatic reorganisation, which took pace between about 6400 and 5000 years ago. This did not involve any large changes in global average temperatures, and was driven by natural processes relating to changes in the Earth’s orbit and the distribution of solar radiation across its surface, rather than the buildup of greenhouse gases from human activity. However, it did involve profound shifts in climatic and environmental conditions across much of the globe, including the desertification of the northern hemisphere subtropical region (southern North America and today’s desert belt stretching from West Africa to China), harsher (and colder) conditions in Europe and other middle and high-latitude regions, and the establishment of a regular El Niño. People practiced small-scale farming and herding, as do billions of people today, and urban societies existed (and became more common and extensive as conditions deteriorated).

The paper summarises evidence from a number of regions suggesting that climatic and environmental change had a profound effect on human societies during this period. The strength of this evidence varies with location, but it is enough for us to construct convincing narratives of environmental change as a dominant driver of social change during key periods. These changes are not always in the same direction – in some places people become more mobile in their search for resources, while in others they retreat to refugia and become more settled. In some locations people give up farming for mobile herding, while in others such herding is abandoned or integrated into a more sedentary lifestyle based on irrigated agriculture. And the effects of large changes in climate go far beyond societal collapse, although that particular outcome has dominated discussions of the impacts of climate change on past societies.

The point is that we can talk about environmental influences on the development of human societies (for better or worse, depending to an extent on your perspective), without falling into the trap of determinism. Another important lesson is that it is naive to stick dogmatically to either a minimalist or a maximalist position. Climatic and environmental changes certainly interact with other drivers of societal change, but the relative importance of these drivers varies over time. Looking to the more distant human past helps us to think about the possibility that some environmental changes may be so great that they overwhelm other drivers of change, even if such a situation is temporary. This certainly seems to have been the case on a number of occasions five to six millennia ago, and I’m prepared to bet that it will be the case again soon.

Here is the first page of the paper (with abstract) – contact me if you would like a full version. References for this and other of my papers on similar topics below.

Brooks, N. 2013. Beyond collapse: climate change and causality during the Middle Holocene Climatic Transition, 6400-5000 years before present (BP). Geografisk Tidsskrift-Danish Journal of Geography 112(2): 93-104. View abstract/1st page, or contact me for an electronic copy.

Brooks, N. 2010. Human responses to climatically-driven landscape change and resource scarcity: Learning from the past and planning for the future. In I. P. Martini and W. Chesworth (eds.) Landscapes and Societies: Selected Cases, pp. 43-66. Springer, Dordrecht, Heidelberg, London, New York, 478 pp. Access chapter via Google Books.

Brooks, N. 2006. Cultural responses to aridity and increased social complexity in the Middle Holocene. Quaternary International 151, 29-49. Download pdf (324 kb).

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About Nick Brooks

Nick Brooks is a climate change specialist with a background in climate science. Nick currently works as an independent consultant, focusing on climate change and international development, climate risk assessment and adaptation. He also conducts research into past climatic changes and their impacts on human societies, focusing on the Middle Holocene and the northern hemisphere sub-tropical arid belt, and the Sahara in particular. Nick is a Visiting Research Fellow at the University of East Anglia, and a co-director of the Western Sahara Project. Nick holds a degree in Geophysics from the University of Edinburgh, and a PhD in climatology from the University of East Anglia.
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