Is killing elephants—legally—the best way to save them? The controversial idea will get a hearing next week at a major conservation meeting in South Africa, where elephant-rich African nations will renew a push to scrap a long-standing global ban on ivory sales and replace it with a limited legal trade in tusks taken from carefully managed elephant populations. A legal market, they argue, will undermine the poaching that is depleting herds and provide a financial incentive for protecting them.

There’s just one problem, a new study says: African elephants grow and reproduce too slowly to support a robust global trade in the material, used for carvings and jewelry. “The demand for ivory is simply too great; it outstrips what elephants can produce,” says biologist David Lusseau of the University of Aberdeen in the United Kingdom, the study’s lead author. Trying to essentially farm African elephants for their tusks will likely “kick them into extinction,” he says.

The study is certain to fuel debate at the 17th meeting of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which runs from 24 September to 5 October in Johannesburg, South Africa. Many African herds are in serious danger: A recent survey of savanna elephant populations estimated that poachers killed 30,000 animals annually between 2007 and 2014, reducing the population to fewer than 400,000. Overall, researchers estimate that African elephant numbers have plummeted more than 95% over the past century.