We regularly hear calls to improve “ocean health.” Health is a powerful metaphor, but scientists have had no way to measure it and therefore no means to evaluate how the world's oceans are doing. More than 60 researchers from a cross section of disciplines and institutions, including the National Center for Ecological Analysis and Synthesis (NCEAS) at the University of California, Santa Barbara, have created the Ocean Health Index to do just that. It rates the health of ocean waters bordering 171 coastal countries and territories. Each nation's overall score is the average of scores for 10 widely held public goals for healthy oceans, including sustainable food provision, recreation, fishing opportunities and biodiversity.


The index, which was published in August in Nature, is not a measure of how pristine the ocean is. (Scientific American is part of Nature Publishing Group.) Instead it measures how sustainably the ocean is providing the things people care about. The goals are universal measures of ecosystem health—all 10 must be met for a country's ocean to be rated as healthy—but the relative importance of each goal can vary from place to place.