The world’s coral reefs do more for the planet than provide underwater beauty.
They buffer shorelines from the effects of hurricanes. An estimated 500 million people earn their livelihoods from the fishing stocks and tourism opportunities reefs provide. The tiny animals that give rise to reefs are even offering hope for new drugs to treat cancer and other diseases.
Despite their importance, warming waters, pollution, ocean acidification, overfishing, and physical destruction are killing coral reefs around the world. Schemes to save those reefs are as creative as they are varied; most recently, scientists released data showing that marine protected areas can help save reefs if they are placed in just the right spots. Genetics is also becoming a larger area of coral research, giving scientists hope they might one day restore reefs with more heat tolerant coral.
But now, in the lead-up to World Oceans Day on June 8, scientists caution that these and other strategies may only buy reefs time until world leaders implement aggressive climate change action.
Without a mix of long-term cuts in emissions and short-term innovation, there’s a not-so-far-off future where coral reefs as we know them simply cease to exist, says Anne Cohen, a coral expert at the Woods Hole Oceanographic Institute in Massachusetts.
Parks under the sea
Scientists often compare coral reefs to underwater rainforests, yet unlike the leafy plant base of a forest, corals are animals. The soft polyps inside the hard parts of corals are naturally translucent and get their famously vibrant colour from algae living inside them.
When corals experience stress from hot temperatures or pollution, they end their symbiotic relationship with this algae, typically expelling them and turning white, though one recent study indicates some coral turn a bright neon colour when stressed. Coral are still alive when they bleach, but they’re at risk—essentially immunocompromised—and many eventually starve and die, turning a dark brown.
People first noticed coral bleaching events in the 1980s. The problem intensified in 2016, when an El Niño weather pattern, which causes warmer waters in the Pacific Ocean, mixed with an already unseasonably warm ocean and killed off a third of the corals on the Great Barrier Reef. Since then, roughly half the corals on Australia’s famous reef have died in subsequent bleaching events, jeopardising an underwater landscape 1,500 miles long.
Scientists around the world are looking for all kinds of ways to protect and maybe even revive corals. One option is to create more marine protected areas—essentially national parks in the ocean. Scientists say creating marine refuges, where fishing, mining, and recreating are off limits, make the reefs healthier, and so more resilient.
An estimated 4,000 fish species, and some 25 percent of marine life, depend on coral reefs at some point in their existence. Fish keep the algae that grow on corals in check, allowing corals to breathe and access sunlight. While an MPA won’t protect corals from heat waves, these natural safe zones can keep fisheries more sustainable in the long term, and fishers around well-managed MPAs often benefit from the “spillover” of healthy fish stocks that populate surrounding waters.
At a talk hosted by the Woods Hole Oceanographic Institute on Wednesday, renowned marine biologist Sylvia Earle promoted the idea of using marine parks to protect coral, which she does through her organisation Mission Blue.
“Reefs that have been protected or not yet exploited by fishing impacts survive when nearby places do not,” she says.
A recently published assessment of 1,800 reefs in 41 countries found that only 5 percent of reefs were able to provide all of their lucrative byproducts, such as healthy fish stocks and biodiversity. To increase that percentage, new marine reserves will need to be strategically placed in areas well away from humans, say experts. It wouldn’t save all reefs, but it would help ensure that more reefs function at 100 percent of their potential instead of just a fraction, says Alan Friedlander, the chief scientist for National Geographic’s Pristine Seas initiative and an ecologist at the University of Hawaii who helped author the reef assessment.
“Without this protection,” he says, “any technological enhancements will suffer the same fate as natural reefs, since the stresses have not abated.”
Innovation to the (immediate) rescue
Beyond such nature preserves, some conservationists are looking to more hands-on methods. One research centre in the Florida Keys is exploring a form of natural selection to keep corals afloat.
The reef system in the Keys has been hit hard by climate change and disease, which is especially tough, because corals there help support fisheries worth an estimated $100 million (£78 million)every year. In addition, corals off Florida’s coasts are polluted by agricultural and sewage runoff.
The additional stress from warming waters is like “the proverbial nail in the coffin,” says Erinn Muller, the science director at the Elizabeth Moore International Centre for Coral Reef Research and Restoration at the Mote Marine Laboratory in Sarasota, Florida.
To keep the wild ecosystem alive, Muller and her team are harvesting samples of the corals that have survived the environmental stresses naturally, breeding them by hand, and reattaching them to the reef. At any given time, the centre has 46,000 corals growing on underwater plastic lattices in its nursery. So far, the centre has regrown over 70,000 corals from five different species on damaged reefs.
