Remotely located in the central Pacific Ocean, south of Hawaii, the Line Islands provide a remarkable research opportunity. The archipelago includes coral reefs reflecting the whole spectrum of environmental conditions—from degraded to pristine. Some islands are heavily populated, with reefs severely damaged by fishing and pollution. Others are uninhabited, with reefs virtually intact. And between these two extremes are reefs at different levels of health. Marine ecologist Enric Sala and a team of researchers visited the islands in 2009 as part of a National Geographic expedition. Studying these reefs will help inform decisions about the minimum size a marine reserve must be to protect coral reefs. Listen to Enric Sala reflect on this expedition in a recorded lecture, "The Last Wild Places in the Ocean."