An energetic unification of ecological theory

Serguei Saavedra

Ecological communities can persist for long periods despite strong competition and environmental variability, yet they can also reorganize or collapse abruptly after seemingly modest change. Explaining persistence, diversity, and collapse has produced several major traditions in ecology, including species-interaction models, consumer--resource theory, coexistence theory, feasibility analysis, and stability theory. These approaches are often developed separately, even though they all describe systems that capture energy from the environment, redistribute it through ecological interactions, and lose it through metabolism. Here I propose an energetic framework that helps place these traditions in a common language. The central idea is that ecological communities persist only when external energy supply can support both the maintenance of biomass and the losses associated with internal redistribution, while remaining within finite supply and throughput limits. For flux-based ecological models, this perspective yields an exact aggregate balance identity; for other model classes, the mapping is partial or reduced-form and depends on how the system boundary is defined. This framework clarifies why persistence is conditional on energetic compatibility, why enrichment need not always promote persistence, and how feasibility, coexistence, stability, and early warning signals can be interpreted as related aspects of the same underlying constraint. It also shows how finite supply and throughput can bound energetically compatible community states, while superlinear scaling of internal throughput provides one simple special case that yields transparent reduced-form limits on community size and, with additional assumptions, on ecological complexity. More broadly, the framework offers a physically grounded way to connect historically separate areas of ecological theory.