The research, spearheaded by Dr. Liam Lachs, indicates that while corals possess some ability to adapt to heat stress through natural selection, this capacity can only mitigate damage if global temperature rise is limited to the goals of the Paris Agreement, specifically capping warming at two degrees Celsius.
Dr. Lachs explained, "The reality is that marine heatwaves are triggering mass coral bleaching mortality events across the world's shallow tropical reef ecosystems. The increasing frequency and intensity of these events is set to ramp up under climate change."
Despite promising experimental research for coral heat tolerance, a critical question remains unanswered. Dr. Lachs stated, "Can adaptation through natural selection keep pace with global warming? Our study shows that scope for adaptation will likely be overwhelmed for moderate to high levels of warming."
The researchers focused their study on coral populations in Palau, located in the western Pacific Ocean. By developing an eco-evolutionary simulation model, the team assessed the impact of thermal and evolutionary biology, along with coral ecology, under different climate scenarios outlined by the Intergovernmental Panel on Climate Change (IPCC).
Co-author Professor Peter Mumby from The University of Queensland warned of the consequences of failing to meet Paris Agreement goals. He noted, "Our world is expected to warm by 3-5 degrees by the end of this century if we do not achieve Paris Agreement commitments. Under such levels of warming, natural selection may be insufficient to ensure the survival of some of the more sensitive yet important coral species."
Dr. Lachs pointed out that current policies place the planet on a trajectory for about 3 C of warming. He stated, "Under this scenario, natural selection for heat tolerance could determine whether some coral populations survive. However, our models predict significant reductions in reef health and a heightened risk of local extinction for thermally sensitive coral species."
Dr. James Guest, leader of the Coralassist Lab and co-author of the study, emphasized the urgency of designing climate-smart management strategies for coral reefs. He remarked, "We need management actions that can maximize the natural capacity for genetic adaptation while also exploring interventions to enhance adaptation in wild populations." One potential approach, still experimental, involves targeted assisted evolution techniques such as selective breeding to improve heat tolerance.
Coral reefs, renowned for their diversity and ecological importance, remain under significant threat. Dr. Lachs concluded, "The results of our models suggest that genetic adaptation could offset some of the projected loss of coral reef functioning and biodiversity over the 21st Century, if rapid climate action can be achieved."