Field ecology is the first of the three levels at which an ecology exists: the larger shared network of participants, conditions, structures, resources, and flows that make up a place or system. It is what people usually mean when they gesture at “the ecology” of a city or an industry.
But no one experiences the whole of it. The field ecology is the common ground; what any given person lives within is their participant ecology — the reachable, consequential subset — and beyond that lies the latent ecology of what could become reachable. Distinguishing the shared field from the effective one is what lets the model explain how two people in the same field can inhabit different worlds, and why measuring the presence of resources in the field says little about whether they reach anyone. See Whose Ecology?.