An international agreement banning the sale of ivory has the african elephant by reducing the benefits of farming poaching trading overgrazing

The correct option is POACHING. 
Poaching involve the act of  illegally killing wild animals. Elephants are normally hunted for the economic importance of the materials that are removed from their bodies. For instance, ivory from an elephant will normally sell for a good price, but the banning of the ivory will reduce the desire of hunters to hunt for the elephants, thus reducing poaching.