Metal scarcity and sustainability, analyzing the necessity to reduce the extraction of scarce metals

There is debate whether or not further growth of metal extraction from the earth's crust will be sustainable in connection with geologic scarcity. Will future generations possibly face a depletion of specific metals? We study whether, for which metals and to what extent the extraction rate would need to be reduced in order to be sustainable. To do so, we propose an operational definition for the sustainable extraction rate of metals. We have divided 42 metals in 4 groups according to their geologic scarcity. Applying the proposed sustainability definition to the 17 scarcest metals, shows that for almost all considered metals the global consumption of primary resources needs to be reduced to stay within sustainable limits as defined in our analysis. The 8 geologically scarcest metals are antimony, bismuth, boron, copper, gold, molybdenum, rhenium and zinc.