As climate change accelerates coral bleaching worldwide, some scientists are proposing a controversial strategy: introducing non-native, heat-tolerant coral species to replace those dying in overheated waters.
Acropora hyacinthus table coral, Lodestone Reef, Queensland, Australia
Michael Webster of New York University and Daniel Schindler of the University of Washington argue that this idea deserves serious consideration. Living coral is critical not only to fish and marine life but to the people who depend on it, Webster told New Scientist. “It provides spaces for different organisms to live. It blocks waves from shorelines; it makes the sand for tropical beaches.”
Unprecedented coral bleaching
According to a report in April by the International Coral Reef Initiative, the most severe global coral bleaching event ever recorded is now affecting 84% of the world’s coral reefs, marking an unprecedented level of damage.
With rising sea temperatures pushing many reefs beyond their thermal limits, corals are expelling the symbiotic algae they depend on, leading to widespread mortality. “Lots of places around the world are quickly losing their coral, and they are having mixed results in trying to bring it back with more conventional tools,” said Webster.
“Pre-adapted” species
Webster and Schindler believe that introducing corals already adapted to warmer climates—known as “pre-adapted” species—could offer a practical lifeline. “You might be able to find corals in a very different place that have already adjusted to the conditions that are arriving at a place, or that might be at that place in the future,” Webster explained.
They point to the Caribbean, where native branching corals are in steep decline. While only two such species are native to the region, over 100 exist globally. Introducing some of these could restore lost reef habitats, even if they look different. “They’re not going to necessarily be the same color or anything like that,” said Webster. “But they’re similar, ecologically.”
Ecological risks
Still, the approach carries significant ecological risks. Non-native corals could introduce new diseases or predators, displace local species or hybridize with them. Yet Webster argues that there are also risks with inaction. “Our best bet for coral reefs is the existing diversity that’s out there,” he said. He considers ecological replacement more feasible than engineering corals genetically to withstand warming seas.
Ongoing debate
Not everyone agrees. Coral ecologist Terry Hughes of James Cook University is a vocal critic. “The benign term ‘ecological replacement’ is naive, dangerous and astonishingly arrogant,” he said.
Hughes cited historical examples where introducing foreign marine species has led to ecological disaster. He recalled how a mysterious Pacific disease entered the Caribbean via the Panama Canal in the 1980s, wiping out algae-eating sea urchins and triggering unchecked algal growth that smothered coral reefs. “Invasive species are a problem for coral reefs, and not a sane solution.”
Webster and Schindler acknowledged these risks, but stressed that the alarming decline in coral cover demanded serious consideration of the idea of ecological replacement.
