Technology evolution is providing new pervasiveservice scenarios characterised by a huge number of distributedand dynamic devices. Accordingly, a new generation of servicesand infrastructures are emerging which support situatedness,adaptivity and diversity. In this paper we model the overallworld of services, data and devices, as a distributed computationalecosystem. As such, each entity will be modelled asan autonomous, spatially-situated individual of the ecosystem,whose existence and state is reified by an LSA (Live SemanticAnnotation). Ecosystem behaviour is controlled by coordinationrules called eco-laws, which are chemical-like reactions evolvingthe population of LSAs.We describe an architecture supportingthis vision along with a model of eco-laws, and show theirusefulness in a scenario of adaptive pervasive displays.