At 135,000 square miles, the Great Barrier Reef reigns as the world's largest living structure. Located off the northeastern coast of Australia, it houses more than 600 species of coral and thousands of other types of marine animals, too. Yet the reef's future looks bleak. In the 27 years from 1985 to 2012, half of its coral cover vanished. A significant proportion of the loss is attributable to climate change, which has strengthened destructive tropical cyclones and made surrounding waters warmer and more acidic. Conservation efforts alone, including protected zones and water-quality improvements, will not do the job. To further combat coral loss, marine biologists at a new research facility in Australia, called the National Sea Simulator (above), have devised a more radical approach: they are manually breeding supercorals capable of living in the increasingly inhospitable sea.

Over the next five years geneticist Madeleine van Oppen and her team will breed global warming–ready corals in a handful of the National Sea Simulator's 33 tanks. Van Oppen can precisely control each tank's salinity, temperature, water quality and pH, which allows her to select for individuals that can withstand stressful environments. A few tanks, for example, replicate the oceanic conditions that models predict for later this century. The specimens most tolerant to heat and low pH will be crossed to breed offspring with these traits and so on down the generations—a process called assisted evolution. The process might happen naturally if corals could adapt quickly enough to their changing habitat, but with little time to spare, humans have stepped in to speed up the clock. “The predictions are very grim for coral reefs,” van Oppen says. “So we feel we have to explore whether assisted evolution is a possible approach that could help us restore the reef.”

Assisted evolution is a novel approach to marine conservation and not without controversy. Some experts are concerned that these supercorals will outcompete the native ones, for example. If van Oppen's work shows success, the Australian government, which funds the National Sea Simulator, could then consider transplanting the laboratory corals onto the Great Barrier Reef. The race against the reef's extinction is on.