Coral reefs face mounting threat from warming oceans

Coral reefs face mounting threat from warming oceans
by Sophie Jenkins
London, UK (SPX) Dec 03, 2024

A new study led by Newcastle University warns that coral adaptation to rising ocean temperatures and more frequent marine heatwaves is unlikely to keep pace with global warming unless global greenhouse gas emissions are drastically reduced.

The research, spearheaded by Dr. Liam Lachs, highlights 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 within the goals of the Paris Agreement, specifically capping warming at two degrees Celsius.

"The reality is that marine heatwaves are triggering mass coral bleaching mortality events across the world's shallow tropical reef ecosystems," explained Dr. Lachs. "The increasing frequency and intensity of these events is set to ramp up under climate change."

While experimental research shows promise for coral heat tolerance, a critical question has remained unanswered. "Can adaptation through natural selection keep pace with global warming?" Dr. Lachs continued. "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. "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 noted that current policies place the planet on a trajectory for about 3 C of warming. "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. "We need management actions that can maximise the natural capacity for genetic adaptation while also exploring interventions to enhance adaptation in wild populations," he said. 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. "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," concluded Dr. Lachs, "if rapid climate action can be achieved."

Research Report:Natural selection could determine whether Acropora corals persist under expected climate change