The purpose of this paper is to demonstrate one way in which an empirically meaningful, formal analytical link between ecosystems and economies might be developed. We broaden traditional approaches to environmental economics by encompassing bioenergetics, but without resorting to energy as the unit of value used by humans. The paper has two main phases. First, an ecosystem model is constructed that exploits standard economic notions of production functions, optimization, and comparative static equilibria. Humans are absent from this phase. In the second phase, humans are introduced under the familiar guise of utility maximizers. This leads to behavior which, via direct and induced changes in the sources and uses of energy, alters the detailed structure of the ecosystem. Empirically testable propositions about changes in this structure are provided, and some existing empirical support is cited. Finally, a proposed methodology is presented for valuing ecosystem components which have no direct use value for humans.