How large is the global population when limited by long term sustainable global metal-, energy- and phosphate supply?

摘要

The WORLD7 model was used to make an assessment for the sustainable metal usage and the resources available within the planetary limits to human society, in order to estimate demands on recycling and maximum metal consumption per capita for different metals. The metals were selected for their importance in society. The calculations of critical metal use show that we have substantial metal usage above the sustainable rates, needing a reduction in net use of more than 95% for many metals. Alternatively, the issue was turned around, asking, if this is how much metals that is available, how many people for how long can we support with it? A sustainability gap can be determined, alternatively, that the global population needs to come down in size to somewhere between 1.5-2 billion people, combined with improved recycling efficiencies. How a global population contraction can take place is not discussed.