Vast changes in the seas are destroying the world’s precious coral reefs at an unprecedented rate and scale. Burgeoning populations, destructive fishing practices, coastal development, sedimentation from forest clearing and unsound agricultural practices, expanding tourism, and increasing pollution are the primary agents of human impact. Over the past decades, managers have largely focused on abating these critical proximate threats to coral reefs, however, during the past 15 years we have witnessed a major new threat to coral reefs—the threat of coral bleaching linked to global warming. While we are still at the early stages of understanding and responding to the coral bleaching threat, there is much that is being learned. IUCN and The Nature Conservancy are committed to providing the marine conservation and management community with information they can use as they carry out “in-the- water” conservation that recognizes and enhances a reef’s natural resistance and resilience. This publication can help inform the people responsible for reef management, as well as the broader public, of the current state of knowledge.