17 October 1989
While African elephants have been hunted for several centuries, the exploitation of elephant herds on a massive scale began in the 1970s. Organized gangs of poachers used automatic weapons, profited from government corruption, and laundered tons of elephant tusks through several African countries to destinations in Eastern and Western countries. The huge increase that occurred during the 1970s was the result of automatic weapons availability and widespread government corruption in many exporting countries, which decimated elephant populations across Africa. In the 1960s, raw ivory prices remained between $3 and $10 per pound. In 1975, the price reached $50 because ivory was perceived as a valuable hedge against rising inflation. By 1987, the price was $125 per pound. In light of these trends, the elephant was faced with extinction in the wild. Eastern African nations such as Kenya lost almost all of their elephants to poachers in the 1980s.  Overall, the elephant population in Africa plummeted from about 1.2 million to 600,000 in the 1980s, prompting the global ban on all ivory trade in 1989.  
References

Nielsen, J.(2002), 'U.N. Eases Ban on Elephant Ivory Trade', from the National Public Radio(NPR) News,12 November, [online], Available at www.npr.org [Accessed: 16 October 2013]|Center for Conservation Biology, Effects of Poaching on African Elephants, [online], Availabe at conservationbiology.net [Accessed: 16 October 2013]