<span>Actually some of the important causes for the age related drop in female fertility is due to some chronic bad habits like chain smoking, regular alcohol intake and taking big dose of drugs, and also due to wrong diet or junky bad food habits, then mainly its due to hormone imbalance problems.</span>
These are things that won't be going away. Natural gasses and fossil fuels will likely run out someday or become much harder to find. When you use these sources of energy, they won't be going away and therefore will be sustainable because we can always continue using them.
