An international group of more than 30 researchers have given a score to every coastal nation on their contribution to the health of the world's oceans, which showed the United States as being slightly above average, and identified food provision, tourism and recreation as leading concerns.

The analysis, published in the journal Nature, scored each nation on a 0-100 scale in 10 separate categories such as clean water, biodiversity, food provision, carbon storage, coastal protection, coastal economies and others.

In this "Ocean Health Index," the world received an average score of 60. The U.S. was at 63.

This is one of the first comprehensive analyses to evaluate the global oceans in so many critical aspects, including natural health and the human dimensions of sustainability. But it's meant less to be a conclusion, the authors said, and more a baseline that can help track either improvements or declines in ocean health going into the future.

"When we conclude that the health of the oceans is 60 on a scale of 100, that doesn't mean we're failing," said Karen McLeod, an ecologist at Oregon State University, director of science at COMPASS, and one of several lead authors on the study.

"Instead, it shows there's room for improvement, suggests where strategic actions can make the biggest difference, and gives us a benchmark against which to evaluate progress over time," she said.

"The index allows us to track what's happening to the whole of ocean health instead of just the parts."

The scores ranged from 36 to 86, with the highest ratings going to Jarvis Island, an uninhabited and relatively pristine coral atoll in the South Pacific Ocean. Many countries in West Africa, the Middle East and Central America scored poorly, while higher ratings went to parts of Northern Europe, Canada, Australia and Japan.

Human activities such as overfishing, coastal development and pollution have altered marine ecosystems and eroded their capacity to provide benefits, the researchers noted in their report.

Among the findings of the study:

+ Developed countries generally, but not always, scored higher than developing countries, usually due to better economies and regulation.

+ Only 5 percent of countries scored higher than 70, and 32 percent were below 50.

+ Biodiversity scores were surprisingly high, in part because few known marine species face outright extinction.

+ The U.S. received some of its best ratings for coastal protection and strong coastal livelihoods and economies.

+ Global food provision is far below its potential, and could be improved if wild-caught fisheries were more sustainably harvested, and sustainable marine aquaculture was increased.

+ Restoration of mangroves, salt marshes, coral reefs and seagrass beds could significantly improve ocean health by addressing multiple goals at once.

+ About half of the goals are getting worse, and this assessment could be overly optimistic if existing regulations are not effectively implemented.

Other primary authors of the report were from the University of California at Santa Barbara, Conservation International, the Union of Concerned Scientists, and the U.S. Commission on Ocean Policy. The work was led by the National Center for Ecological Analysis and Synthesis, and Conservation International.

The researchers said they hope the analysis will help inform public policy and management.