I'm not expert, but I think it would be taking in account the biologcal hierarchy relationships in which emergent properties araise in each stage.
Environmental economics could not take into consideration more than the generality of the context, while ecology implies consideration in the parts and in the whole, not only biological (at the communities, populations, individuals) but in social relations, in knowledge, times, culture and others (cfr. Renovar la teoría crítica y reinventar la emancipación social (encuentros en Buenos Aire, Boaventura de Sousa Santos)
Thus, Ecological economics ventures into Political Ecology (wich is a complex social scince), while environmental economics referes to aspects of the physical resources, mangment and legislation.