Throughout history, the human desire for ivory—used in products from jewelry to piano keys to priceless religious art objects—has far outmatched efforts to stop the killing of African elephants for their tusks. In 2012, investigative journalists Bryan Christy and Aidan Hartley explored the illegal ivory trade and the plight of Africa’s elephants, and documented their work in the National Geographic special Battle for the Elephants.

This video excerpt from that film explores the history of the ivory trade and the resulting devastation of Africa’s elephant population—from 26 million elephants in 1800 to fewer than one million today. The clip examines factors that fueled the “ivory frenzy” of the early 1900s and documents the steady and startling decline in the elephant population. A worldwide ban on ivory sales in 1989 led to a rebound in the population, to about a million. But in 1999 and 2008, due to pressure from countries in Asia and southern Africa, the Convention on International Trade in Endangered Species (CITES) allowed two sanctioned sales of ivory. The video looks at attempts to stem the killing—attempts that largely have proven unsuccessful, evidenced by the fact that more than 25,000 elephants were killed in Africa in 2012 alone.