Trying to protect or restore an ecosystem has something in common with playing the stock market or the roulette wheel. Unexpected surprises are part of the equation. Just one example: Limits on old growth logging in the Pacific Northwest in the 1990s were supposed to save spotted owls. But the bird’s numbers have continued plummeting in the face of invading barred owls.
So it should come as no surprise that a group of coral researchers are adopting a strategy more commonly associated with Wall Street and Las Vegas as they try to increase the odds that coral reefs survive climate change.
Just as financial wizards put their money into a variety of investments to guard against market gyrations and gamblers spread their bets on horse races to increase the chance they profit; these scientists have just laid out a strategy to “hedge” against the unpredictability of the future.
There is one safe bet when it comes to coral: Things are getting worse. Rising ocean temperatures and marine heatwaves have already taken a toll on coral reefs, some of the most ecologically rich places on the planet. Australia’s Great Barrier Reef has lost half its coral in the past quarter century. One recent study predicted that if average global temperatures rise more than 1.5°C above pre-industrial levels, more than 99% of coral reefs won’t survive. Imagine 99% of all forests dying.
In the face of such an existential threat, a number of coral scientists are scrambling to find ways to help coral endure in the wild. They are scouring coral genetics looking for signs of heat tolerance, working to accelerate evolution by breeding lab-raised coral in hot water, and taking steps toward industrial-scale aquaculture aimed at replenishing depleted reefs with farmed coral.
But with over 600 coral species just in the Great Barrier Reef, there’s no way to save them all. And right now, the mix of species being grown for planting won’t necessarily fill all the niches critical to a healthy reef. “Current coral restoration programs tend to focus on easy-to-collect, fast-growing coral species, which have similar characteristics and cannot support ecosystem services on their own,” warned Madeleine van Oppen, a coral geneticist at Australia’s University of Melbourne and a leading figure in the push to help coral adapt to a hotter world.
She recently helped convene a group of scientists to wrestle with the question of how to decide which species it makes the most sense to save. “If a program only has funds to focus on 20 or 30 coral species, it will want to focus on the sets of species to get the most ecosystem bang for its buck,” she said.
The scientists devised a two-pronged approach designed to identify which corals are best suited to survive, while also ensuring the collection of corals cover all the key roles needed to keep a reef ecosystem functioning. As a test case, they looked at a breakdown of key traits of nearly 400 species found in eastern Australia – among them, how robust their coral skeletons are, how quickly they grow, and how big their colonies become. They also weighed characteristics that would help them survive destructive underwater heatwaves, such as resistance to bleaching from heat.
“The ecosystem services coral reefs provide us, such as coastal protection and fisheries, depend upon coral species with a broad range of ‘life history strategies’, for example slow to fast growing, mounding to branching shapes, and under to upper story,” explained Joshua Madin, a coral researcher at the Hawai’i Institute of Marine Biology and the lead author of the new study.
The scientists used computer programs to compare the characteristics of each species, choosing among ones that had overlapping traits and played similar roles in the ecosystem. For each set of traits, they favored the corals that seem better equipped to cope with hotter waters. The end result was a list of 11 corals that in combination were likely to provide the broadest ecological benefit with the best chance of persevering, as well as a longer list of 28 top contenders, the scientists reported July 2 in the Journal of Applied Ecology.
By contrast, a current restoration program in Australia isn’t doing enough to hedge its bets, the scientists found. The Coral Nurture Program there has selected 39 species of coral to rear, based on how common they are and how easy they are to plant in the reef. But those species cover only around half of the key traits found among different corals on a reef, the researchers reported.
At a time when humanity is gambling with the future shape of Earth’s ecosystems, they might want to try a new betting strategy.
Madin, et. al. “Selecting coral species for reef restoration.” Journal of Applied Ecology. July 2, 2023.
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