Culture and deforestation in the Pacific: A phylogenetic perspective

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My colleagues and I conducted a comparative study of pre-European deforestation and reforestation (referred to hereafter as ‘forest outcomes’) on 70 Pacific islands (Atkinson et al 2016). Our aim was to see if any cultural, especially agriculture and land ownership norms, or geographic aspects of locations on those islands were associated with forest outcomes.

We published the results of the study in PLoS ONE, an open-access journal published by the Public Library of Science.

Atkinson QD, Coomber T, Passmore S, Greenhill SJ, Kushnick G (2016) Cultural and Environmental Predictors of Pre-European Deforestation on Pacific Islands. PLoS ONE 11(5): e0156340.  Link   PDF

Using comparative methods one can test hypotheses about functional relationships (i.e., about cause and effect). It is like choosing 100 kids that vary in candy consumption and testing the hypothesis that, if sugar causes cavities, you should see more cavities in the kids that eat more candy.

Of course, without conducting a controlled experiment, it’s hard to say anything definitively about causation. Poor health habits, for instance, may lead to eating tons of candy and never brushing your teeth. In those 100 candy eaters, was the higher incidence of cavities due to candy or poor dental hygiene?

The same goes in comparative cross-cultural studies like the one we’ve conducted. There are inter-dependencies in the data for a number of reasons, including shared environments and cultural history (for example, is there really a causal relationship between mountainous environment and prevalence of polyandry, or is there just a cluster of Himalayan societies that all live in the mountains and that all engage in this practice because their ancestors did?)

To control for cultural history and shared environments, we used phylogenetic methods — yes, the ones used more commonly in evolutionary biology to look at evolutionary relationships amongst species.

We found that geographic and cultural factors are associated with forest outcomes, but there was little phylogenetic signal. This suggests “that forest outcomes were not tightly constrained by colonists’ cultural ancestry, but instead reflect a combination of ecological constraints and short-term responses of each culture in the face of those constraints” (Atkinson et al 2016).

What was my role in the study?

I was enlisted by the lead author of this study to help provide data on land tenure for the societies on the focal islands. This required many hours of work reading dusty, early 20th century tomes on Pacific ethnography — which I loved of course. I also provided feedback on the analyses and helped to write the paper.

My previous work on the evolution of land tenure norms in societies of SE Asia and the Pacific was published in 2014. Click here to download that paper.

2 Comments

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2 responses to “Culture and deforestation in the Pacific: A phylogenetic perspective

  1. Hi Jeff

    Just a note about your paper. Interesting stuff though I suppose the conclusions aren’t surprising…The results certainly seem to make sense. One issue: Necker and Nihoa were never deforested according to biologists (diamond and others are wrong on this issue). How would that change your results?

    Liked by 1 person

  2. geokush

    Hi Carl — Thanks for the question. It’s been a long time since we were both students at UW, but I’ve been a fan of your work on Rapa Nui for a while and I know you have a pretty sophisticated understanding of the sorts of methods we’re using.

    Most of the variation in deforestation falls into the lower ranges, with Necker and Nihoa 2 of the 4 data points that we considered high levels of deforestation. My quick-and-dirty take would be that they aren’t likely to be super influential in shaping the statistical relationships of interest. But, really it’s hard to tell in a multivariate analysis, especially one like this where we control for phylogeny and other things, without re-doing them either (a) without those two points, or (b) with those two points re-coded.

    Can you point me to the evidence about the lack of deforestation on Necker and Nihoa?

    Like

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