The gist of the talk, anyway, is that depletion is not an isolated problem. Minerals are part of the geological cycles of the Earth. When we extract a mineral and we disperse it all over the ecosystem we cause changes of all kinds, besides the obvious fact that we use non renewable resources. So, for instance, when we extract fossil fuels we alter the climate. The two problems: fossil fuel depletion and climate change are two sides of the same coin. And that is true of all the minerals we use - in most cases depletion is just one side of a larger problem.
Thanks to professor Marcus Kracht for having organized this presentation in Bielefeld.