What is the future sustainable population for the earth?
The sustainable population is, in mathematical terms, a dependent variable — which is why it is represented on the vertical axis of the graph. The independent variables on which it depends are biocapacity and footprint (rate of consumption). Increase the footprint — and/or decrease biocapacity — and the maximum sustainable population decreases — and vice-versa. It is clearly neither moral nor desirable to instantly reduce today’s world population of 6.7 billion to a sustainable level of 5.1 billion by, for example, dispatching 24% of each country’s population. It is, therefore, not helpful to discuss sustainable populations in today’s terms. Assumptions need be made about conditions expected to exist when the sustainable level is deemed to be achieved. Thus, Earth’s sustainable population in (say) 2050 will depend on how much world population will be consuming each year at that time. This is not an a priori definable quantity, since the global biocapacity, collective consumption, expec
