All ecosystems and their sub-components have a certain capacity for alteration and for the absorption of pollution and stress before they lose their integrity and deteriorate into another state. If the limits of this capacity are not understood, human communities can quickly destroy the ability of the relevant system to sustainability provide the services upon which the community depends. History provides numerous examples of major cities (Carthage, Petra, 17th century Venice) that have collapsed as a result of depletion of the resource base or alternation of pre-existing ecosystems.
Carrying capacities in human ecosystems cannot be entirely defined in biophysical terms. Carrying capacity reflects the level of damage to a system that a human community is willing to accept based upon the amount of services or resources that a community requires from the system, and the point at which damage makes the system unable to met these requirements.
Carrying capacities can sometimes be increased through small changes in human processes that provide for the efficient use of materials, energy and nutrients throughout the ecosystem or one of its sub-systems.