Assisted evolution, selectively breeding corals to survive marine heatwaves, is one of conservation's most discussed ideas. A Newcastle University team has now put numbers on what it would actually take. Using a pedigree-tracked coral population maintained for eight years, the researchers mapped family relationships, estimated how traits such as growth, reproduction and survival are inherited, and modelled each coral's genetic merit for heat tolerance.
The conclusions, published in Current Biology, are bracing. Selection must target long-term heatwave survival itself, or traits strongly genetically correlated with it, rather than convenient proxies. And to keep pace with projected warming, breeders would need to select only the top 1 to 5 percent most tolerant corals as broodstock, repeating that intense selection over multiple generations while somehow maintaining genetic diversity and scaling operations to meaningful reef areas.
There was encouragement amid the rigour: the team found no detectable negative genetic correlations among the traits studied, meaning breeding for heat tolerance need not obviously sacrifice growth or fecundity. But the researchers are emphatic that assisted evolution is a complement to emissions cuts, not a substitute. Without slowing the warming itself, even ruthless selection cannot keep corals ahead of the curve.