"Africa's rapidly growing human population is predicted to more than double by 2050 - a staggering increase of three and a half million people per month," he added.
"There is no question that this increase puts wildlife and habitat under enormous pressure.
"Urbanisation, infrastructure development, cultivation - all good things in themselves, but they will have a terrible impact unless we begin to plan and to take measures now."
Poor water supplies, overgrazing and illegal animal trading are also to blame, he said.
The trade is particularly "barbaric".
"The world is a worse place for it, and we must stamp it out. "
The UK has recently announced plans to restrict sales of ivory within the country.