In contrast, Figure 6-3 captures the essence of the ecological economics model that makes three major modifi cations to the environmental economics model: (1) waste products generated by both consumers and producers have a feedback loop, which means that such products have the capacity to negatively impact the production system from which they are generated; (2) there is a specifi c inclusion of certain natural resources as inputs such as clean air, clean water, and assimilative capacity; and (3) most important, there is an ecological system that includes at least 17 ecological services . The fundamental premise of this major conceptual revision is that the economic system is embedded in the ecological system, cannot function without it, and is ultimately subject to the same laws and constraints that apply to natural systems.