Biology subjects

Scaggs, S. A.

Publications and source records attributed to Scaggs, S. A..

3 recordsLinked to original sources

bioRxiv2025

Signatures of adaptive self-organization detected in swidden societies worldwide

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.

ecology↗

bioRxiv2025

The Landscape Ecology of Swidden: A Global Comparison Indicates Swidden Landscape Mosaics Contribute to Vegetation Diversity at Intermediate Levels of Disturbance

Swidden agriculture is a widespread anthropogenic disturbance regime in tropical forests. Swidden research often posits that aggregate levels of forest disturbance correlate with increased land degradation, however a landscape configuration approach may distinguish when swidden degrades landscapes and when it diversifies them. Here we analyze how the configuration of swidden mosaics relates to vegetation diversity. Using satellite imagery from 18 swidden societies across the African, Southeast Asian, and American tropics, we quantify patch geometry using landscape metrics and estimate vegetation diversity from spectral variation and develop a nonlinear hierarchical Bayesian model that links the structure of swidden mosaics with vegetation diversity. Our analyses reveal three dominant gradients of swidden mosaic patterns: (1) aggregation versus interspersion of land-cover types; (2) spatial dispersion versus synchronization of disturbed patches; and (3) alternative modes of landscape connectivity. Across sites, vegetation diversity exhibits a consistent nonlinear response, peaking at intermediate levels of disturbance intensity. These results demonstrate that swidden agriculture does not produce a singular, degradative outcome. Instead, its effects on vegetation diversity depend on how disturbance is spatially configured. By shifting attention from area-based measures of deforestation to landscape configuration, this study reframes swidden as a spatial process with the potential for diversity-enhancing outcomes.

ecology↗

bioRxiv2024

A complex adaptive systems model of labor reciprocity and normative reasoning in swidden agriculture

Swidden (aka "slash-and-burn") agriculture is a prototypical coupled human and natural system and understanding the social, cultural, and environmental factors shaping the trajectories of swidden forests is essential to mitigate climate change and ensure equitable collaboration between scientists, planners, and Indigenous communities. Despite this, mathematical models integrating its social and ecological dynamics are rare. Here, we use complex adaptive systems theory to develop a model where individuals rely on labor exchange driven by reciprocity, and on normative reasoning that can lead to sanctions. Our results identify three emergent regimes: low-intensity swidden, sustainable high-intensity swidden that maximizes ecosystem services and harvest returns, and deforestation. We show that sustainable high-intensity swidden evolves if labor reciprocity and normative reasoning are balanced: helping behavior should be significantly conditioned by normative reasoning to prevent over-harvesting, while reciprocity is necessary to prevent excessive sanctioning. We find that the sustainable high-intensity swidden regime is robust to changes in group size, is resilient to environmental shocks, can evolve under various models of forest ecology, and is most productive for both forests and farmers when the balance of labor reciprocity and normative reasoning results in an intermediate scale of forest disturbance. Overall, we illuminate the importance of Indigenous social norms and customary practices related to swidden labor in maintaining sustainable and intensive swidden agriculture.

ecology↗