The Yemeni island Socotra, off the tip of the Horn of Africa in the Arabian Sea, is so isolated that nearly 700 of its species are found nowhere else on Earth. The island’s bitter aloe has valuable pharmaceutical and medicinal properties, and the red sap of Dracaena cinnabari, above, was once thought to be the blood of dragons.

And this is only what remains after two millennia of human settlement; the island once featured wetlands and pastures that were home to crocodiles and water buffaloes. Tanzanian zoologist Jonathan Kingdon says, “The animals and plants that remain represent a degraded fraction of what once existed.”