Researching human-environment systems always implies to navigate a delicate balance. On the one hand, every scientific activity strives to identify generalities and regular patterns of causations, reduce complexity to extract the key dimensions of a problem, perhaps even arrive to some form of predictive capacity about the dynamics of the systems studied. On the other hand, complexity, contingency, and context-dependence are fundamental features of human-environment systems, and research is also about uncovering, acknowledging, and finding ways to manage such systems.
Land system science has been balancing between these two aspirations. Simple, caricatural narratives about the relations between human societies and environment, such as the tragedy of the commons, which dominated early human-environment research, have been challenged and substituted by an increasing awareness of contingency and context-dependence. Further, being a field originally based on a very strong methodological focus (on remote sensing and other geospatial technologies, land use modelling tools, and others) and relying to a large extent on case studies, land system science has often been regarded as a field where theoretical progresses were slow or even practically nonexistent.
In a new paper co-authored by many researchers from GLP and beyond, we argue that after decades of accumulating scientific work, our community is now in a position to consolidate theoretical insights on the dynamics of land systems in a way that both (i) builds on the very strong interdisciplinary character of land system science, and (ii) navigates the balance between generalization and contingency.
We build on the idea of "middle-range" theory, coming from sociologist Robert Merton, which strives for a balance between highly stylized narratives from "grand theories" and ad hoc explanations of singular cases. Here, we define middle-range theories as contextual generalizations that describe chains of causal mechanisms explaining a well-bounded range of phenomena, as well as the conditions that trigger, enable, or prevent these causal chains.
We first discuss the articulation between theories, frameworks, models, and typologies. We then review the different theories explaining changes in land-use extent and intensity, such as deforestation, agricultural intensification, or frontier development. We then synthesize them into middle-range theories of higher-level processes of land system changes, focusing on land-use spillovers and land-use transitions as non-linear, structural changes, including processes of land sparing and rebound-effect, leakage and indirect land-use change, and forest transitions.
A similar approach articulating chains of causal mechanisms, and the conditions and contexts under which they operate, could be applied to other land and social-ecological systems processes to enrich the portfolio of middle-range theories. Theories of change for sustainability governance would be strengthened by building on causal chains derived from such middle-range theories.