Modeling post-Pleistocene megafauna extinctions as complex social-ecological systems

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The role of human hunting behavior versus climate change in the mass extinction of megafauna during the Late Quaternary is much debated. To move beyond monocausal arguments, we treat human–megafauna–environment relationships as social–ecological systems from a complex adaptive systems perspective, to create an agent-based model that tests how human hunting may interact with environmental stress and animal life history to affect the probability of extinction. Using the extinction of Syncerus antiquus in South Africa at 12–10 ka as a loose inspirational case study, we parameterized a set of experiments to identify cross-feedbacks among environmental dynamics, prey life history, and human hunting pressure that affect extinction probability in a non-linear way. An important anthropogenic boundary condition emerges when hunting strategies interrupt prey animal breeding cycles. This effect is amplified in patchy, highly seasonal environments to increase the chances of extinction. This modeling approach to human behavior and biodiversity loss helps us understand how these types of cross-feedback effects and boundary conditions emerge as system components interact and change. We argue that this approach can help translate archaeological data and insight about past extinction for use in understanding and combating the current mass extinction crisis.

We are currently amid a highly accelerated anthropogenic extinction event conservatively estimated to be one hundred times higher than expected background rates (Ceballos et al., Reference Ceballos, Ehrlich, Barnosky, García, Pringle and Palmer 2015). It is estimated that 48% of animal species are currently in decline (Finn et al., Reference Finn, Grattarola and Pincheira-Donoso 2023) and that 50% of the plant and animal species on Earth may be lost by 2100 (Braje and Erlandson, Reference Braje and Erlandson 2013, p. 21). Biologists have identified four recent periods of significant acceleration in the extinction rate of land animals (63.8–32.2 ka, 16–9.5 ka, 2300–600 yr, and 180–120 yr) (Andermann et al., Reference Andermann, Faurby, Turvey, Antonelli and Silvestro 2020). There is a general temporal correlation between the dispersal of anatomically modern humans and the demise of faunal species around the world (Braje and Erlandson, Reference Braje and Erlandson 2013; Boivin et al., Reference Boivin, Zeder, Fuller, Crowther, Larson, Erlandson, Denham and Petraglia 2016), but the role of human-driven effects versus climate-driven effects in these extinctions continues to be debated (Barnosky et al., Reference Barnosky, Koch, Feranec, Wing and Shabel 2004; Koch and Barnosky, Reference Koch and Barnosky 2006; Braje and Erlandson, Reference Braje and Erlandson 2013).

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