A mass extinction of ocean life may be imminent, but it is not inevitable, a new study reports in Science. Excessive harvesting from fisheries is only part of the threat. The greater risk to ocean dwellers stems from the destruction of habitats as a result of industrial activity. As atmospheric carbon rises, more of it is taken up by the oceans, making seawater more acidic. At the same time, rising temperatures have accelerated the decline of coral reefs, and high-tech fishing methods and deep sea mining have destroyed fragile ecosystems. Despite this grave situation, the authors do not counsel despair because of the ultimate resilience of the oceans and the opportunity for corrective action. If we act soon enough to mitigate climate change and limit the exploitation of the oceans, we can chart a course to healthier oceans and a healthier planet.