Jennifer Jacquet Jeremy B. C. Jackson Today, “the high seas” are generally understood to refer to the vast expanses of open oceans that are not under the formal jurisdiction of any nation. Legally, the high seas are defined as the 60% expanse of the oceans that lie beyond national exclusive economic zones, which are within 200 nautical miles (370 km) of coastlines. Despite legal definitions, however, the expanses of the high seas are neither well-defined nor well-understood from ecological or geological perspectives. The surface area of these waters is one-and-a-half times the total land area on the planet and the dynamics in their depths play critical roles in regulating climate and biogeochemical cycles, supporting incalculable biodiversity and providing rare habitat to some of the most charismatic species on Earth. Like the continent of Antarctica and the canopy of the Amazon, the high seas are places that few will experience but remain sources of wonder and imagination for people of all nations and cultures. Today, the sustainable health of the high seas is at risk. Industrial activities are already draining the oceans of their natural capital including valuable minerals, new genetic resources, and wild animals. This set of research articles on the science of the high seas has been compiled to underscore some of the major challenges and risks that nations face as ocean exploitation accelerates. Each study explores a particular facet of human influence on the high seas …