Reef Relief

For years, coral reefs around the world have been dying off, often because of rising ocean temperatures, threatening fish and other wildlife and also human livelihoods.

Now, one team of researchers believes they may be on the way to stopping the destruction – by breeding corals with improved heat tolerance.

“This (research) shows that selective breeding is feasible,” said Liam Lachs of the United Kingdom’s Newcastle University, and lead author of a new study on the selective breeding of corals for heat tolerance published in Nature.

Rising ocean temperatures have triggered coral bleaching – when coral loses the symbiotic microalgae that gives them their color and nutrients – making coral more susceptible to die-off. Marine heat waves, rising carbon dioxide levels and also overfishing have already led to the loss of half of all coral reefs on Earth since the 1950s, according to the Natural History Museum of Australia.

The scientists, attempting to address this issue, decided to try selective breeding. Used for thousands of years to enhance desirable traits in plants and animals, wrote Interesting Engineering, researchers decided to try using the method for nature conservation, marking the first attempt ever to selectively breed adult corals to withstand increasingly frequent marine heatwaves.

First, the researchers bred coral in a lab. Afterward, they conducted two tests, one exposing both the parent coral and the offspring to an intense 10-day “heatwave” with temperatures rising by 3.5 degrees Celsius (6 degrees Fahrenheit). In the other test, they exposed coral to a one-month “heatwave” by increasing temperatures by 2.5 degrees Celsius. Both trials mirrored actual marine heatwave conditions.

The offspring of corals bred for high heat tolerance outperformed their parents. That means that selective breeding can improve heat tolerance in just one generation, researchers said. The improvement in tolerance was 1 degree Celsius over one week.

However, the improvement of 1 degree Celsius is modest in comparison with future marine heat waves that are expected under full-blown climate change, Phys.org reported.

Lachs, the study’s lead author, highlighted the importance of the discovery of selective breeding’s feasibility, but stressed it wasn’t a “silver bullet solution.” “In parallel, rapid reductions of global greenhouse gas emissions are an absolute requirement to mitigate warming and give corals an opportunity to adapt,” he said.

Still, the research is seen as proof that breeding corals to withstand heat is possible. The study’s authors said there was a great need for further research in selective breeding techniques and how to implement such methods in real-world scenarios, along with climate action initiatives to help curb global warming.