Interdisciplinary linkages of biophysical processes and resilience theory: Pursuing predictability

The global value of ecosystem services is approximately $33 trillion per year. Given the economic value, it is not surprising that billions of dollars are spent annually to protect, preserve, restore and conserve natural resources. Resilience describes the ability of ecological systems to recover from disturbance. Resilient ecosystems remain productive and thus maintain services including biophysical processes that are important for human well-being. Four system-wide characteristics, or biophysical signatures are reviewed, at least one of which is required to relate ecosystem structure or function to resilience. Biophysical signatures include (a) variable material and energy recycling, (b) biodiversity, (c) the rate of governing processes, and (d) bioenergetics. Fast recycling rates encourage ecosystem stability by dampening oscillations while slow recycling rates increase resistance by weakly propagating disturbances. The role of biodiversity in stabilizing ecosystems may be viewed as either a functional redundancy where increased diversity resists perturbation by maintaining key ecosystem functions, or as response diversity that ensures recovery processes. Governing ecosystem processes that respond slowly, such as those involving large storage reservoirs, resist perturbation and shift to alternative states. Several observational resilience studies featured bioenergetics as both the perturbation force (i.e., predation, food supply) and the thermodynamic orientor that organizes recovery (i.e., maximizing exergy storage). An energy balance approach is proposed as a possible method to assess ecosystem stability. Validating a mechanistic resilience model against high resolution data collected from a system undergoing regime shift is needed to advance theory toward practical application. As physical requirements bound the possibility space for ecosystems, it is not surprising that biophysical processes play a central role in resilience theory.

► Four characteristics are required to relate ecosystem function to resilience.
► Governing ecosystem processes resist perturbation and shift to alternative states.
► Ecosystem services are maintained by resilient systems.
► A simple physically based method is proposed for ecosystem stability assessment.