Balancing the community's CO 2 to O 2 exchange is a critical indicator of a sustainable system. Modeling the input and output of water resources of a site provides another challenging indicator for sustainability. Precycling to eliminate excess and non-recyclable packaging and products is important to reducing consumption. Sustainability can be modeled by a site or society's percentage use of renewable versus non-renewable energy resources. Full sustainability would require a site or society to completely shift to renewable energy systems.
Human ecology defines the final and most inclusive indicator.
Human ecology can and often does include the other four more biological indicators. The biological variables are separated in this model for clarity and emphasis with the conviction that they are more ecologically fundamental to society's ability to define, model, and measure sustainable development. Evaluating a community's commitment and action programs towards a sustainable future is critical in modeling this all inclusive variable. These interrelationships demonstrate the importance of modeling and measuring the selected set of indicators for sustainability. The existing use of each resource.