Ecosystems,externalities, and economies

This paper incorporates an ecosystem model into a model of a simple economy. The decisionmaking agents in the ecosystem are individual organisms aggregated to the species level. A species may provide utility directly to humans, or it may provide utility indirectly because it is used either as a raw material in goods fabrication or as sustenance for other species. We describe a comparative static equilibrium of the ecosystem where species' demands for other species are equal to the supplies of those other species, and energy is conserved. The ecosystem is then embedded in the economy so that the effects of human intervention can be traced through both the ecosystem and the economy. Human intervention creates ecosystem externalities such that ecosystem equilibria are shifted and the new equilibria affect the utility or the production processes of other humans. This framework allows us to describe in principle which ecosystem services can be efficiently usurped by humans, which waste flows can be efficiently allowed into ecosystems, and which ecosystem organisms and physical attributes can be efficiently maintained.