You’d never know the end of coral reefs was nigh listening to ocean scientist Meaghan Johnson talk about staghorn coral restoration efforts off the coast of Florida.
When I spoke with Johnson last summer, the world was in the midst of a long-lasting global reef die-off caused by bleaching, when over-heated water disrupts the life cycle of the corals. Scientists were waving giant red flags about reefs, as studies suggested a 90 percent decline unless global warming is capped at 1.5 degrees Celsius.
“We can’t not do this. We can’t not try,” Johnson said, as she started to describe her work for The Nature Conservancy in the Dry Tortugas, where she and other divers had planted about 1,500 cuttings of nursery grown staghorn coral in a network of test plots in protected waters.
“They are surviving,” she said. “We’re learning each year how genetics play a role, how they develop in the different sites. We’re going to be doing this until there are no more corals left.”
It’s a race against time and tide, and the outcome has consequences for coastal ecosystems and communities, and by extension, the rest of us. Coral reefs are vital ecosystem service providers: Nurseries for countless fish species; buffers against hurricanes and rising sea level; and beach-builders in most tropical areas.
Staghorns—branched corals that look a little like underwater saguaros—once thrived in vast groves from north of Miami to the tip of the Florida Keys. But in the last 30 years, more than 80 percent of the staghorn coral around Florida died as the ocean warmed and pollution increased.
Now, it’s a regional poster child for the global decline of reefs, dwindling so fast that it’s on the International Union for the Conservation of Nature Red List. It’s also listed on the U.S. federal Endangered Species List.
But Johnson and other coral specialists are preparing to try and re-establish staghorns on an ecosystem level. One area of focus is offshore Miami, where a healthy coral reef could provide billions of dollars of storm protection to the vulnerable metropolis.
The earliest restoration experiments started in 2004 and some projects got another boost as part of the 2009 American Recovery and Reinvestment Act, early in the Obama presidency. International partnerships could also help expand the restoration program into the wider Caribbean, bolstering resilience on islands threatened by climate change.
Helped by citizen scientists and volunteers, coral experts have developed a network of Florida coral nurseries, where cuttings taken from healthy reefs are nurtured until they’re big enough to replant in the targeted areas.
“Part of our program is to identify areas where the reefs are less susceptible. We’re trying to identify genotypes of corals that are more resistant to disease and bleaching,” Johnson said.
The restoration process is sustainable, and could be pursued on a larger scale, according to a recent study based on detailed monitoring in the restoration areas, the nurseries and the harvest areas. Overall, the study evaluated how 120 distinct genotypes or staghorn corals within six geographical regions responded to the harvest, nursery propagation and out-planting.
“There’s been no impact on wild colonies since we started. The survival rate in nurseries is 80 percent or greater, and the coral out-plants have greater than 70 percent survivorship,” said Stephanie Schopmeyer, a University of Miami coral researcher who co-authored the study in the journal Coral Reefs. The source areas are scoured to carefully to make sure there’s no disease, and the scientists never collect more than 10 percent,” she said.
“Success will be healthy, growing sexually reproducing staghorn colonies. The ultimate goal is to keep on planting coral until we’re out of a job,” she said.
Other data from the study can be used in combination with climate models the project ocean temperatures, and oceanographic information about currents and historic coral habitat to pinpoint the best spots for restoration, she said. There are at least 80 different projects under way in Florida, and many more similar efforts around the world.
Those efforts started in 2005, with simple transplantation of corals from one spot to another. For the last five years, the concept of coral gardening has been expanding rapidly as the scientists learned they could propagate healthy coral branches to increase overall numbers.
Staghorn corals are particularly important for Florida and the rest of the Caribbean because they grow fast and provide an essential framework for diverse reef ecosystems.
The fast growth also makes them suitable for restoration. In good conditions, staghorns can grow 4 inches per year. The stalks that are transferred from nurseries out to restoration sites are often about 20 inches with multiple branches. Depending on conditions in the restoration areas, they are attached to cinderblocks with epoxy, or twist-tied to Christmas tree-like structures suspended near the seafloor with cables.
It’s a labor-intensive process that couldn’t succeed without volunteers, said Schopmeyer.
“It takes some time,” she said. “For sure the bottleneck is the actual out planting. At about an hour per diver we can get anywhere from 20-50 corals out. When we start talking about restoring on an ecosystem level, that’s a lot of hours underwater.”
She acknowledges the projections of a global coral wipeout, but said that good science offers at least a fighting chance to improve the odds for coral survival.
“It’s a very scary possibility that the water might just be too warm. But we’re looking at different genotypes, and recent studies have shown there’s definitely a genetic component to bleaching,” she said, describing how divers have discovered side-by-side examples where one staghorn colony dies during a bleaching episode, while another colony, exposed to the same conditions, survives.
“So we’re trying to out-plant a genetically diverse population,”she said. “The big push is to try and understand the genetic component.”
Now that the scientists know they can help recolonize staghorn coral, they have also started to try growing more challenging specimens, including elkhorn, another branching variety, as well as some of the massive, pillow- or boulder-like species that were listed as endangered in 2015.
The first results suggest those species could also be propagated in nurseries, although the growth rates are slower, and the process starts from smaller pieces.
Scientists are also trying new micro-fragging techniques, starting with individual coral polyps, to see of they can spur better growth. There have been some promising results in a land-based coral nursery, but Schopmeyer said that technique results in a lot of tissue growth, but less skeletal development.
“We want to take this to the reef and the ecosystem level. It’s really time to start scaling this up and making significant impacts,” she said.
Measuring that impact will not be easy. There are thousands of species spread across millions of square miles of oceans, growing in thin skeins near coastlines, fringing remote Pacific islands, and clumping in massive pillows in the warm Caribbean. Put all together, corals would cover just 0.1 percent of the Earth’s surface, about the size of France.
But they are disproportionately important ecosystems. According to the United Nations Environmental Program’s Coral Reef Unit, reefs are found in or near more than 100 countries and provide critical ecosystem services, including food security and livelihoods from fisheries, and tourism. According to UNEP, together with mangroves and sea-grass beds, coral reefs deliver the highest annual value in terms of ecosystem services of all natural ecosystems on the planet.
The most recent global level assessment of coral health dates back to 2008, predating the mass bleaching of 2010, and there is currently no globally coordinated monitoring program for reefs. The 2008 figures from the Global Coral Reef Monitoring Network show the world has already lost 19 percent of its coral reef areas, with 15 percent threatened by 2030 and another 20 percent by 2050.
Those projections were made without considering the most recent global warming data—or that effective future management may conserve more coral reefs.
But 46 percent of the world’s reefs are regarded as being relatively healthy and not under any immediate threats of destruction, except for the “currently unpredictable” global climate threat, said Ilsa Kuffner, a U.S. Geological Survey coral researcher.