Exploring the effects of feedbacks on land system behaviour : A Complex Adaptive Systems approach

Abstract

Land systems are Complex Adaptive Systems (CAS) — they are composed of heterogeneous and autonomous entities who interact with each other and with their environment. Land system dynamics take place at the interface of land use, soil, climate, market, technology and policy, in which processes are linked to each other in the form of feedbacks between subsystems and across scale levels. These feedbacks often result in nonlinear behaviour, which challenges our understanding and management of land systems. The ability of land system models to represent, investigate, and understand feedbacks is made possible, largely due to the recent developments in Agent-Based Models (ABM), which grow in parallel with CAS research. This thesis aims to contribute to the knowledge on the effects of feedbacks on land system behaviour. To do so I systematically review existing models and construct a series of ABMs to explore the effects of feedbacks. In Chapter 1, I introduce land systems as Complex Adaptive Systems, the importance of studying land system feedbacks, and the thesis outline. In chapter 2, I provide a review on the current state of the art regarding feedback representations in land models. In chapter 3, I introduce a stylised land use ABM in which feedbacks are incorporated to explore how they result in nonlinear system behaviour. In chapter 4, the stylised ABM is modified to explore under what conditions land system hysteresis emerge. In chapter 5, the complexity of the stylised ABM is further increased to assess land system resilience. Results are synthesised in chapter 6 to provide insights into land system complexity and the effects of feedbacks. The synthesis is followed by critical reflections on model representation and recommendations on land system science, modelling, and policymaking. To conclude, in this thesis feedbacks are explored in terms of their effects on complex land system behaviour. Specifically, feedbacks are found to exist between different subsystems and scale levels, to result in distinctive types of behaviour, to affect the existence of hysteresis, and to contribute to land system resilience.