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Behind the Restorative Effects of Coral Gardening

The technique involves planting fragments of nursery-raised coral on reefs in the wild to replenish depleted colonies.

It's not just the Great Barrier Reef—coral reefs around the globe are in decline due to climate change, ocean pollution, and a number of other impacts of human activities on marine environments.

But new research finds that "coral gardening," which involves planting fragments of nursery-raised coral on reefs in the wild to replenish depleted coral colonies, is playing a key role in the restoration of staghorn coral reef systems in the Caribbean—and might just help inform strategies to ensure the long-term survival of the world's coral reefs in the future.

A study published in the journal Coral Reefs in June looks at how successful restoration efforts have been at several sites in Florida and Puerto Rico over the first two years of a staghorn coral gardening program. The researchers behind the study—a team led by scientists with the Rosenstiel School of Marine and Atmospheric Science at the University of Miami—say they found that current restoration methods do not cause excessive damage to donor colonies (from which coral tissue is taken and propagated in a nursery), and that, once the coral fragments are planted back out in the wild, known as being "outplanted," they behave just like wild colonies.

Particularly susceptible to bleaching, staghorn coral populations have declined more than 80 percent over the past 30 years due to higher incidence of disease and the effects of global warming, especially higher ocean temperatures and ocean acidification, according to the International Union for the Conservation of Nature. The species was listed as threatened under the Endangered Species Act in 2006 and is currently listed as critically endangered on the IUCN Red List.

There have been efforts to propagate and reintroduce A. cervicornis in waters near the Dominican Republic, Florida, Honduras, Jamaica, and Puerto Rico, the IUCN reports.

"Coral reefs are declining at an alarming rate and coral restoration programs are now considered an essential component to coral conservation and management [planning]," Diego Lirman, a professor of marine biology and ecology at the University of Miami and co-author of the study, said in a statement.

Lirman and the rest of the team collected data on the survival and productivity of thousands of individual A. cervicornis colonies within six different geographical regions in order to develop benchmarks that can be used to assess coral reef restoration efforts and their effect on the overall ecosystem. "Our findings provide the necessary scientific benchmarks to evaluate restoration progress moving forward," Lirman added.

"We propose that up to 10 [percent] of the biomass can be collected from healthy, large A. cervicornis donor colonies for nursery propagation," the researchers write in the study. They also propose a number of benchmarks for the first year of staghorn coral restoration efforts: greater than 75 percent live tissue cover remaining on donor colonies; greater than 80 percent survival of nursery corals; and greater than 70 percent survival of outplanted corals.

The world's wild coral reef systems provide habitat for fisheries, supply food for humans and numerous marine species, and help protect shorelines against hurricanes and other extreme weather events. That's why coral restoration is coming to be seen as an effective means of ensuring coral reef systems are still capable of providing those ecosystem services as well as for mitigating the effects of rising sea levels and storm surges on coastlines, according to University of Miami coral biologist Stephanie Schopmeyer, lead author of the study.

"Our study showed that current restoration methods are very effective," Schopmeyer said in a statement. "Healthy coral reefs are essential to our everyday life and successful coral restoration has been proven as a recovery tool for lost coastal resources."

This story originally appeared at the website of global conservation news service Get updates on their stories delivered to your inbox, or follow @Mongabay on Facebook, Instagram, or Twitter.