Populations of the three species have declined: savanna elephants, the largest land animals on the planet, trundling across sub-Saharan Africa; forest elephants, their straight-tusked cousins, navigating the shadows of Africa’s equatorial woodlands; and the smaller-eared Asian elephants, about a third of which live in captivity.

And we’re to blame. We’ve expanded into elephant territory, building homes and roads, felling forests and planting crops. More cruelly, people have indulged their desire for ivory trinkets that come from a dead elephant’s tusk. Although elephants are difficult to count, one estimate suggests that the African continent may have been home to some 26 million elephants at the beginning of the 19th century.