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Humans are helping coral evolve to survive climate change

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Reefs are in so much trouble that they may need human help to adapt

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The climate is changing too rapidly for coral reefs to adapt, so researchers in Australia and Hawaii have proposed a novel solution: help them adapt faster.

The researchers call the approach "assisted evolution." In a sense, it’s the same thing we’ve been doing with domesticated plants and animals for thousands of years, cross-breeding organisms for desirable traits. But the idea of using these methods for the purposes of conservation is new. The traits that scientists are looking for aren’t things like faster growth or more edible meat, but the ability to survive in a changing environment. The researchers admit their approach is "extremely novel" and view the project as a proof of concept, according to the paper published in PNAS earlier this week.

They call the approach "assisted evolution."

Conservation is traditionally understood as, well, conservation — setting aside land where habitats can thrive free from human meddling. Ironically, this often requires a great deal of human meddling. Humans help endangered birds breed, then teach them their migratory routes, and maybe even develop complex markets to rent land for them to rest on during their flights. People have to drive (or shoot) salmon around stretches of river that have become too dry or dammed for them to pass on their own. The coral project goes a step further, proposing that we modify the animals themselves.

Madeleine Van Oppen, a researcher at the Australian Institute of Marine Science and the lead author of the paper, acknowledges that this will be controversial. The idea of modifying a species and introducing it to the wild in the hopes that it crossbreeds and spreads is a departure from traditional conservation, with its focus on preservation and the elimination of invasive species. But it’s easy to see how you get there once you start thinking about how to deal with a problem as vast as climate change. Many reefs are already set aside as conservation areas, but that’s not enough when the entire ocean is changing at an unprecedented rate.

Conservation often demands a great deal of human meddling

"Some people have objections in principle to any manipulations," says van Oppen, "but I think these manipulations are pretty minor. Plus climate change demands it." Even if these methods work, she says, "We’ll never be able to preserve everything."

Coral reefs in the Caribbean, Australia, and elsewhere have seen drastic declines in recent years, as ocean water gets warmer and more acidic. They’re also under pressure from pollution, like nutrient runoff, and invasive predators, like coral-eating starfish. In Australia, a recent survey found that the Great Barrier Reef had lost over half its initial coral cover, and another study predicted that coral could decline to under 10 percent if warming trends continue. Much of that change is already locked into the climate system and would occur even if we manage to curb CO2 emissions tomorrow. (Obviously, it will be far worse if we don’t.) Van Oppen says we need to focus on reducing CO2, but we should also think about new ways of coping with change that at this point is inevitable.

"Climate change demands it."

"We’re developing a toolbox," says van Oppen, emphasizing that any release of improved corals would only happen after extensive impact studies and public discussion.

Van Oppen’s team is using a machine called the Sea Simulator to mimic the future state of the ocean. It's essentially a giant aquarium that allows researchers to tweak temperature, acidity, salinity, and other variables simultaneously. For example, van Oppen can expose her corals to the predicted ocean temperature and acidity of a reef off the coast of Australia, down to modeled ocean cycles, and grow them over a period of several years.

By exposing coral to the hot, acidic water of future seas, van Oppen hopes to find corals that can weather the change, then breed them with other hardy types. Van Oppen will be crossing between closely related species, as well as within single species, looking for traits that confer resilience to climate change.

And it’s not just the coral. Van Oppen will also be attempting to manipulate the bacteria and algae that live within coral; they have a faster rate of evolution, and may play a role in the ability of coral to withstand high temperature. When coral "bleaches," a symptom of stress, it’s because it jettisons its symbiotic algae, weakening its immune system. If more resilient algae can be evolved, the researchers hope, maybe it could make the coral more resilient too.

"We're developing a tool-box."

"When we cross within species, we’re looking for individuals with certain traits," says van Oppen. "When we cross different species, we’re just hoping we’re lucky and get some positive phenotypic results." She cites an example in the Caribbean, where two species of coral in highly damaged environments hybridized on their own. Such natural hybridization may occur more frequently than previously thought. "It happens naturally, we want to see if we can we harness these mechanisms to help the coral become more resilient."

Traditional conservation efforts already keep genetic diversity and adaptation in mind. The Nature Conservancy has been trying to restore dying reefs in the Caribbean for the last decade or so, partly by planting them with staghorn and elkhorn corals, which have seen massive die-offs since the 1980s. Right now they’re trying to collect genetically diverse samples and put them on the reef where they can breed and maybe evolve, says James Byrne, the Conservancy’s marine program manager. "Our theory is that the remaining pool is too far apart to breed."

As for a more aggressive and intentional breeding program like the one being tested, Byrne says there may come a time when that’s necessary. "This approach they're talking about takes it a step farther," says Byrne. "We may get there, we may have to start looking at that. I think it’s great people are looking at it now."