Botswana's Okavango Delta was named the 1,000th World Heritage Site by UNESCO this week, a hard-won designation that affords special protection against human development.

The delta encompasses a 3,000-square-mile (7,770 square kilometers) plain whose nutrient-rich water provides a sanctuary of channels, lagoons, and islands for thousands of plant and animal species. Among the area's inhabitants: the largest population of elephants on Earth.After some initial work to expand the delta's tourism infrastructure, the delta's new status will bring a halt to development.—Jennifer S. Holland