There's no consensus on just how many of Africa's elephants are left. The World Wildlife Fund, for example, estimates that the population could be as few as 470,000 and as many as 690,000. Whatever the exact figure, it's clear that China's demand for ivory has created significant financial incentives for poachers to hunt the herds that remain scattered across the continent.
On Monday, a group of researchers published what they billed "the most comprehensive assessment of illegal ivory harvest to date." Their conclusion, based on two methods of assessing illegal killing, is that poaching has not only reduced elephant populations, but it has also become unsustainable. The problem, beyond how many elephants are being killed, is the lack of surviving males in their prime years.