The Landscape Ecology of Swidden: A Global Comparison Indicates Swidden Landscape Mosaics Contribute to Vegetation Diversity at Intermediate Levels of Disturbance
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Purpose
Swidden agriculture is one of the most significant agricultural developments in human history and it has major ecological implications for the structure of the landscapes where it is practiced, yet it has long been theorized to be a primary cause of deforestation. Few studies have explored the structure of swidden mosaics and its relationship to vegetation diversity over large spatial scales.
Methods
We classify satellite imagery from 18 swidden societies in the African, SE Asian, and American tropics using a random forest model and a segment anything model. We use landscape metrics to describe variation in the composition and configuration of swidden mosaics and develop a nonlinear Bayesian model, accompanied by general mathematical solution, to model the relationship between the local structure of swidden disturbances and vegetation diversity measured from spectral variation.
Results
Our analysis shows that swidden landscapes can be distinguished by their spatial entropy, connectivity, and patch synchronization. Our modeling results show that amid this variation, several swidden landscapes exhibit a non-linear relationship in which vegetation diversity peaks at intermediate levels of swidden disturbance.
Conclusion
By using approaches from landscape ecology to study the heterogeneity of swidden mosaics, we provide evidence that swidden practices can change landscape structure in ways that increase vegetation diversity when the scale of swidden disturbances occurs at an intermediate level. We suggest that this conclusion provides new insights into the potential environmental outcomes of swidden cultivation which may have significant theoretical implications for interpretations of human paleoecology during the Holocene, and contemporary issues of sustainability.
