Elephants , WWF. Once common throughout Africa and Asia, elephant numbers fell dramatically in the 19th and 20th centuries, largely due to the ivory tradeivory tradeThe ivory trade is the commercial, often illegal trade in the ivory tusks of the hippopotamus, walrus, narwhal, mammoth, and most commonly, African and Asian elephants. Ivory has been traded for hundreds of years by people in Africa and Asia, resulting in restrictions and bans.