What guides regime transitions in ecohydrological systems?

Changes in ecohydrological systems are driven by emergent patterns of organization that arise through internal differentiation, reflected in the variability of ecosystem components and shifts in the strengths of positive and negative feedbacks. This phenomenon, known as self-organization, allows ecosystems to transition between self-organized states in response to external perturbations, leading to new dynamic regimes. The resulting overall emergent properties represent a balance between the loss of stability and shifts toward equilibrium within ecosystems. However, it remains unclear whether ecosystem self-organization is guided by a convergence of states and feedbacks toward an optimal state and, if so, what such an optimal state might look like.

Using information-theoretic approaches, we characterize ecosystem variability and feedbacks as entropy changes based on observations. To do so, we concentrate on eddy-covariance measurements from global FLUXNET stations. Our findings reveal potential optimal states toward which ecosystems tend to transition and identify the conditions that govern these transitions, shaping the evolutionary trajectories of ecosystems. These results also provide a framework for assessing ecosystem resilience to major perturbations, such as droughts and heatwaves, and emphasize the critical role of hydrological variability in improving predictions of ecosystem changes and extreme events that pose risks to water and food security.