He added: "Endless people can travel to visit a rare African animal during its lifetime - creating a renewable source of tourist dollars that cycles through a local economy over and over again. Yet no matter how high the price, only one person can kill a black rhino and then it is gone forever, just like Cecil."
In just 40 years, the black rhino population has been decimated because of poaching and hunting. Today, according to CNN's coverage of Knowlton's hunt, there are just 5,000 rhinos left in the world. According to other estimates, there are fewer than half that: Just 2,500 black rhinos left on earth.