Dying coral reefs. Sea turtles choking on plastic trash. Plummeting fish stocks.

There seems to be a never-ending daily drumbeat of negative ocean news, which can obscure progress in marine preservation. Case in point: A study published Wednesday in the journal PLOS ONE found that ocean health has remained more or less stable over the past five years.

The findings are based on a review of the Ocean Health Index, an effort that began in 2012 to annually collect and analyze diverse sets of data to measure nations’ current and likely future progress in meeting a set of 10 goals, including the preservation of biodiversity, fisheries and coastal protection.

The index, a collaboration between the National Center for Ecological Analysis and Synthesis (NCEAS) at the University of California, Santa Barbara, environmental group Conservation International and other institutions, gives countries scores of 0 to 100 to rate efforts toward achieving the goals. A top score of 100 indicates that a goal is being sustainably met, such as ensuring that fish stocks are not overexploited.

“The Ocean Health Index is designed to give us a big-picture, comprehensive view of ocean health rather than just focusing on how fisheries or tourism or biodiversity are doing,” said study lead author Benjamin Halpern, the executive director of NCEAS and a professor at U.C. Santa Barbara. “It gives us a view of how things are changing over time, and once you have that you can understand what’s driving those changes and what the consequences may be.”

And so, for example, the index does not look at coral reef bleaching in isolation but in context of broader impacts. (The study did not include data on the most recent bleaching events that have devastated the Great Barrier Reef and other reefs worldwide.)

Map and distribution of Ocean Health Index scores and average yearly change in scores. (Benjamin Halpern et al.)

Data is perhaps one of the most crucial, if overlooked, linchpins of growing efforts to protect the ocean from climate change, overfishing, plastic pollution and other threats. In June, for instance, 193 nations reaffirmed at the United Nations Ocean Conference a commitment to achieve seven targets to restore ocean health by, among other things, reducing the impact of ocean acidification, curtailing overfishing and protecting 10 percent of the ocean in marine reserves by 2020.

Left unresolved was how to measure progress toward meeting those targets. It is a Herculean task. The Ocean Health Index, for instance, collects and analyzes dozens of data sets from national, international and nongovernmental sources.

“One of the most vexing and surprising challenges is getting good information on coastal livelihoods and economies,” said Halpern. “And we have just a tiny portion of the ocean floor mapped, but those habitats are so important for biodiversity. It’s a pretty fundamental gap in our knowledge.”

Data gaps are likely to grow narrower in the years ahead, thanks to efforts like Google’s Global Fishing Watch, which detects patterns of illegal fishing by crunching billions of data points generated by the movements of 250,000 fishing vessels around the world.

The Ocean Health Index study offers a snapshot of marine health since 2012, by which time the ocean was already suffering degradation from climate change, overfishing and pollution.

Still, “The last five years have seen notable improvements in some aspects of ocean health and worrisome declines in others, with substantial variation among different regions (countries or territories) around the world,” the study’s authors wrote.

For instance, the rapid expansion of marine protected areas around the world in recent years signaled improved ocean health as did improved scores for biodiversity and fisheries. “Many regions are extracting fewer natural resources relative to their historical peak,” according to the study.

Scores decreased, however, for coastal protection, due largely to sea ice loss in Arctic and sub-Arctic regions that impacted ocean health. Overall, the global Ocean Health Index score remained stable at 71 between 2012 and 2016.

“The creation of marine protected areas is having a noticeable improvement on ocean health and we can use that information to guide other actions in other countries,” Halpern said. “There’s plenty of bad news about coral bleaching, too much trash in the ocean, too much overfishing. To know that actions are being taken and are making improvements in ocean health is really valuable. To give hope and optimism about humanity being able to make a difference in the oceans is an important message.”