After two years of effort, an international team of 65 scientists, policymakers and environmentalists has completed the first phase of what might appear to be an impossible task: assessing the health of the ocean and assigning it a 'score'.

Their conclusion? Out of a possible score of 100, the ocean's health rates a 60. The lowest score – 36 – went to the waters off Sierra Leone, while the waters surrounding uninhabited Jarvis Island, near Hawaii, merited an 86. United States waters averaged a score of 63.

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To determine the scores, the authors assessed ten diverse public goals – food provision, carbon storage, tourism and recreation, biodiversity, artisanal fishing opportunities, coastal protection, sense of place, natural products, coastal livelihoods and economies, and clean waters – and calculated the index for every coastal country: a total of 171 nations and territories. The high seas are not included in the index; its authors hope to add them within the next year or two.

Each goal was evaluated on the basis of four criteria. Present Status is a goal’s current value (based on the most recent available data) compared to a reference point. Trend is the average percent change in the present status for the most recent 5 years of data. Pressures are the ecological and social pressures that negatively affect scores for a goal. Resilience is the sum of the ecological factors and social initiatives (such as policies or laws) that can positively affect scores for a goal by reducing or eliminating pressures.

The score for each goal is the average of the values for the Present Status and Likely Future Status, with the latter determined by combining the Trend, Pressures, and Resilience values. Within that combination, the authors assigned Trend twice as much weight as the combined role of Resilience and Pressures, because trends are a more direct measure of the future trajectory of a goal, while resilience measures require more time to take effect, and changes are often slow to register.

Launching the index, via publication of a paper in Nature this week, is, the authors hope, only the beginning. Lead author Ben Halpern of the University of California, Santa Barbara said it was “just the launch pad for what will hopefully be the much larger and more substantial effort of engaging with people.”

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In addition to adding the high seas in due course, Halpern and colleagues plan to update the index annually, and anticipate it providing the basis for national, regional and international ocean management. They point out that individual countries can use it to judge their own success or failure, and that they can make those judgments according to their own emphases: for example, if their priority is to extract the maximum amount of fish from their waters, they can assign that the greatest weight, and adjust their score accordingly. Alternatively, if they wish to focus their score on efforts to protect their marine resources from exploitation, they can do that too.

The effort has a fan in NOAA Administrator Jane Lubchenco, who called it “a great leap forward in society’s attempts to understand what the trade-offs are for management decisions.”

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IMAGE: Tomato Clownfish in Bulb-Tentacle Sea Anemone (Amphiprion frenatus in Entacmaea quadricolor) Solomon Islands. (Corbis)