Coral reefs have been dying off at alarming rates because of modern human activity, and conservationists struggle to preserve them. Now scientists have found such efforts have a long history.

By the beginning of the 15th century, native Hawaiian islanders were engaging in sustainable practices to preserve their reefs — ushering in 400 years of recovery.

The research, published Monday in the journal PLoS One, shows that sustainable practices go back a long way and that coral reefs may be better able to regenerate than previously thought.

Coral reefs are some of the world's richest ecosystems, supporting a diverse array of marine life, including reef fish and mollusks. But they're highly susceptible to modern-day threats such as changing water temperatures, pollution and aggressive fishing practices....