Ecological metabolism names the fact that an ecology does not merely hold things — it takes them in, transforms them, circulates them, and produces consequences. A city draws in resources, energy, people, information, and capital and turns them into work, relationships, culture, waste, innovation, wealth, institutions, and knowledge. A healthy field has functioning flows; an unhealthy one shows blockages, overconcentration, depletion, toxic accumulation, starvation, poor circulation, and failed renewal.
The consequence for the model is decisive: circulation, not inventory, is what matters. A billion dollars sitting idle is not ecological capacity; its value depends on whether it can reach relationships where it becomes useful. Information that never reaches affected participants is stranded; human ability that never finds an interface through which to participate is stranded. This is why the model measures flows rather than stocks, and why the same problem appears at the scale of a single life as a latent ecology that never circulates into reach. See How a Living Field Works.