Sand is probably one of the natural elements that surrounds us the most and we never truly realise how much. Sand + Gravel + Cement = Concrete. Now concrete is something we actually see. Have a look at this -> Sand Mining <-. The importance of sand in human development is astounding and the impact we are having on animal and human ecosystems in areas where we source this material is catastrophic.
Two topics come to my mind. First, sand-recycling. For those who live in big cities, it is likely cranes are an everyday part of the paysage. New buildings are being built up everyday. At the same time older buildings and houses are brought down. Could there be a connection? Is it possible to use sand from old constructions to avoid new sand use? Is it economically viable? To what extent? Don't know but it might make sense. Second, replace sand. Do we know any material that can be largely used to replace sand and keep fuelling urban growth? (because it will for sure continue).