A comprehensive survey of corals has turned up billions of colonies across the Pacific Ocean. The work—based on actual head counts, satellite data, and informed estimates—suggests many species are not in immediate danger of extinction, and the census could help conservationists and policymakers make better decisions about how to protect reefs.
The numbers are “incredibly encouraging,” says Nancy Knowlton, a retired coral reef biologist at the Smithsonian Institution’s National Museum of Natural History. “The biggest take-home message is that it’s not hopeless, even if corals have been painted as the canary in the coal mine.” And although some researchers worry this abundance could lead policymakers to ease up on efforts to protect reefs, Knowlton says, “having a clear set of numbers makes it easier to figure out what to do next.”
Over the past several decades, corals have suffered tremendous damage from warming seas, which causes bleaching, a process that causes stressed corals to lose the algal partners they need to survive. Corals are also being assaulted by ocean acidification, which can harm their ability to build their hard frames, as well as by pollution, overfishing, oil spills, and other human activities. In some places, such as the Caribbean, coral numbers have dwindled and, overall, the extent of coral reefs is half what it was in the 1870s. Experts have warned that most coral reefs could be gone by 2100. Already, about one-third of the world’s 6000 known coral species are listed on the International Union for Conservation of Nature’s (IUCN’s) Red List of Threatened Species. On the other hand, some reefs are proving resilient to marine heat waves or have continued to thrive against all odds.