The main threat in nonsustainable development

"From a resource point of view, the main threat in nonsustainable development is not so much that we are running out of non-renewables (for instance fossil fuels or heavy metals). The main threat is that the productivity of our renewable resource base (vital ecosystems) is declining. The main problem is that waste molecules from the use of nonrenewables have negative effects on our renewable resource base through climate change, acid rain, eutrophy, toxic metals, etc."

Karl-Henrik Robèrt (founder of The Natural Step), commentary in E.F. Schumacher Small is beautiful.