Metabolic Theory of Ecology

The metabolic theory of ecology proposes that an organism's metabolic rate, the pace at which it converts energy and materials to sustain itself, grow and reproduce, is a fundamental driver that predictably shapes ecological patterns across many different levels, from an individual organism's own life history up through population growth rates and the structure of entire ecosystems. Ecologists James Brown, James Gillooly, Andrew Allen, Van Savage and Geoffrey West presented the theory in its now-standard, fully developed form in an influential 2004 paper, building on earlier foundational work relating metabolic rate to body size and temperature, including a widely used scaling relationship West and his colleagues had proposed several years earlier. The theory holds that metabolic rate scales in a predictable, mathematically describable way with an organism's body size and body temperature, and that this underlying metabolic scaling relationship can then be used to predict a wide range of higher-level ecological quantities, including population growth rates, the density of organisms an environment can support, and the overall flow of energy and material through an ecosystem. The metabolic theory of ecology has been influential in providing ecology with a single quantitative, mechanistic framework linking individual-level physiology to ecosystem-level patterns, though it has also drawn sustained scientific debate over how precisely and universally its proposed scaling relationships actually hold across the very wide range of organisms and ecosystems found in nature.