If you could pick one substance (that will eventually run out) to save, what would it be???

Question: If you could pick one substance (that will eventually run out) to save, what would it be???
- Keywords:
  save
Asked by TMH.23 LFC! to Huma, Jack, Lucy, Miranda, Peter on 17 Nov 2016.
- Miranda Bane answered on 17 Nov 2016:
  
  I would like to save clean water. At the rate we are going we will run out of clean water and then we will have to come up with complicated and expensive ways to clean it. Clean water is so important because all of life is dependent on it.

Question: If you could pick one substance (that will eventually run out) to save, what would it be???