This article treats the environmental dimension of the Greater Paris system.It shows how a territorial ecology approach permits the cogent investigation of governance principles and policy options for the Greater Paris region.First we present estimates of synthetic indicators such as the ecological footprint and the environmental footprint that allow us to quantify the scale of environmental impact of the mega-city.Then we consider, with an integrated modeling and scenario analysis, the "metabolism" of Greater Paris as illustrated by the impacts of economic activity in the Seine River catchment on the Seine Estuary downstream. This example highlights the important scope for territorial policies based on ecosystem quality considerations and, more widely, the need to accord a central place to the environmental dimension for strategic visions of possible futures of the Paris mega-city.
