Culture and deforestation in the Pacific: A phylogenetic perspective

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.