Combating Climate Effects: Unprecedented Growth in Climate Resilience Observed in Pacific Coral Reef

A study conducted under the leadership of Newcastle University has discovered that the coral reefs in the Pacific Ocean’s Palau region have most likely adapted to increased ocean temperatures, thus mitigating potential future bleaching that could be induced by climate change. (Location: Koror, Palau.)

In the Pacific Ocean’s Palau area, coral reefs are displaying enhanced tolerance to thermal conditions, possibly alleviating future bleaching caused by climate change. The research underscores an immediate need to reduce global carbon emissions and adhere to the terms of the Paris Agreement to safeguard these essential ecosystems.

Coral reefs in a particular section of the Pacific Ocean seem to have adapted to escalated ocean temperatures, possibly lessening the future consequences of climate change in terms of bleaching, as the new findings reveal.

Focusing on the Pacific Island nation of Palau, the study orchestrated by Newcastle University has revealed that there is potential for historic growth in the coral reefs’ thermal tolerance. The results portray how this ability could mitigate the future impacts of bleaching, contingent on the reduction of global carbon emissions.

By utilizing several years of field observation, the researchers simulated numerous potential future paths for coral bleaching in the reefs of Palau, with varying anticipated rates of thermal tolerance improvement. The findings revealed that substantial reductions in bleaching effects are plausible if the coral’s thermal tolerance continues to increase at the most likely historical rate throughout the 21st century.

Published Results and Implications

The study, published on August 22 in the journal Nature Communications, corroborates the scientific agreement that future coral bleaching’s severity is tied to reducing carbon emissions. It shows that high-frequency bleaching can be entirely avoided at specific reefs under scenarios of low-to-middle emissions, such as compliance with the Paris Agreement. However, such bleaching consequences are inevitable if society continues to depend on fossil-fuel development under high emissions scenarios.

Using decades-long field observations, the researchers formed numerous possible future paths for coral bleaching in Palau’s reefs, each having a unique projected rate of thermal tolerance growth. (Credit: Liam Lachs, image of Palau coral reef.)

The principal investigator, Liam Lachs, affiliated with Newcastle University’s Coralassist lab, expressed, “Our research highlights ecological resilience to climate change but simultaneously emphasizes the urgent need to adhere to the Paris Agreement to effectively safeguard coral reefs. We identified a natural augmentation in coral thermal tolerance over multiple decades, comparable to the ocean warming rate. Though our research offers a glimpse of optimism, it also underscores the persistent necessity for action to diminish carbon emissions, to mitigate climate change, and to ensure these crucial ecosystems’ future.”

Dr. James Guest, the study’s co-author from Newcastle University’s School of Natural and Environmental Sciences, added his insights by stating, “We understand that coral reefs can heighten their overall thermal tolerance over time through acclimatization, genetic adaptation, or shifts in community structure, yet our knowledge of the pace of this occurrence is scant. This study uses data from a remote Pacific coral reef system to estimate the thermal tolerance increase rate since the late 1980s. The outcomes provide a semblance of hope that reefs can cope with rising temperatures, but only if robust action is taken to combat climate change.”

Collaborative Research and Wider Perspective

The lead author’s collaborative visit in 2021 to work with Professor Simon Donner’s Climate and Coastal Ecosystems Laboratory at the University of British Columbia, Canada, led to this study.

Professor Donner remarked, “This research illustrates the potential for certain coral reefs to become more resilient to impending climate change-driven heat waves. Such resilience might also bear a cost, impacting reef diversity and growth. Without significant reductions in greenhouse gas emissions within the next two or three decades, Pacific reefs won’t provide the resources and wave protection that Pacific inhabitants have relied upon for generations.”

Future of Coral Reefs

Coral reefs, despite being reservoirs of extraordinary biodiversity, are experiencing unparalleled declines due to marine heatwaves and associated mass coral bleaching and mortality events. To survive climate change, coral communities must withstand increasingly severe and frequent marine heatwaves.

The natural rate of increase in coral reefs’ thermal tolerance, and whether this can keep pace with ocean warming, has mostly remained a mystery. To bridge this understanding gap and provide insight into the coral communities’ future resilience, the Newcastle University team explored historic mass bleaching occurrences, centering on Palau, a remote Pacific coral reef system.

The study also examined varying degrees of global action to mitigate climate change and reduce carbon emissions, probing four emissions scenarios and their effects on future coral bleaching projections.

Based on the findings, the thermal tolerance of Palau’s corals seems to have risen by 0.1 °C per decade since the late 1980s. This increment indicates that innate mechanisms like genetic adaptation, acclimatization of corals, or alterations in their symbiotic microalgae might have played a part in enhancing coral thermal tolerance.

Co-author Professor Peter Mumby of the University of Queensland and Palau International Coral Reef Center observed that “unraveling the driving mechanisms behind these potential shifts in tolerance and comprehending the possibility of ongoing future growth in thermal tolerance will constitute some of the forthcoming challenges.”

Reference: “Emergent increase in coral thermal tolerance reduces mass bleaching under climate change” by Liam Lachs, Simon Donner, Peter J. Mumby, John C. Bythell, Adriana Humanes, Holly K. East, and James R. Guest, 22 August 2023, Nature Communications. DOI: 10.1038/s41467-023-40601-6

Frequently Asked Questions (FAQs) about coral reefs

More about coral reefs

• Newcastle University
• Nature Communications
• Paris Agreement
• University of British Columbia Climate and Coastal Ecosystems Laboratory
• University of Queensland
• Palau International Coral Reef Center
• Emergent increase in coral thermal tolerance reduces mass bleaching under climate change