Signatures of adaptive self-organization detected in swidden societies worldwide

Abstract

Quantitative signatures of adaptive self-organization and the spatial scale of human management can be detected in anthropogenic landscapes. Yet, while abundant evidence for self-organization in physical and natural systems exists, there are few adaptive self-organization models that can explain coupled dynamics of human subsistence systems that have also been rigorously validated. Here, we analyze over 18,000 forest patches extracted from 18 remotely-sensed swidden mosaics from tropical and subtropical regions across the planet. We discover a power law signature of adaptive self-organization in the size of the patches and correlation distances that indicate the spatial scale of socioecological adaptation. To explain this pattern, we propose a mathematical model of swidden labor reciprocity, normative reasoning, field placement, forest disturbance and regrowth dynamics that explains the emergent spatial structure of swidden mosaics. Social self-organization can promote sustainable levels of forest disturbance when ecological dynamics such as facilitation, seed-dispersal and competition are conditioned by social dynamics, giving rise to power-law land-use patterns. We use simulations to explore the emergent properties of the model and identify two regimes: deforestation and sustainable swidden. When we analyze the relationship between the simulation results in the remote sensing data, we find that 16/18 of the study areas exhibit power-law distributions and spatial correlation patterns that match the sustainable swidden regime in the model. These findings support the hypothesis that adaptive self-organization may be a general characteristic of coupled human and natural systems.