Measurements of strong sustainability use a completely different model from weak sustainability, they start out with ideal end-states. Two widely used examples of this analysis are measurements of the minimization of ecological footprint and the optimization of material flows.
We have not covered how to do this yet!
In the next modules, we will delve into the details of material and energy flow and how we can use the principles of thermodynamics to assess how efficiently we are using these resources.
To finalize... The difference between our current state and strong sustainability is termed the Sustainability Gap. At the current rates of resource use and extraction, we are following patterns of resource depletion:
Depletion of matter: use leads to decreasing concentration. Non-renewables are materials that, once dispersed, will not spontaneously re-concentrate. Depletion of energy: use leads to transformation into unusable energy (e.g., heat).