The 2014-17 Global Coral Bleaching Event: The Most Severe and Widespread Coral Reef Destruction

Abstract

Ocean warming is increasing the incidence, scale, and severity of global-scale coral bleaching and mortality, culminating in the third global coral bleaching event that occurred during record marine heatwaves of 2014-2017. While local effects of these events have been widely reported, the global implications remain unknown. Analysis of 15,066 reef surveys during 2014-2017 revealed that 80% of surveyed reefs experienced significant coral bleaching and 35% experienced significant coral mortality. The global extent of significant coral bleaching and mortality was assessed by extrapolating results from reef surveys using comprehensive remote-sensing data of regional heat stress. This model predicted that 51% of the world’s coral reefs suffered significant bleaching and 15% significant mortality, surpassing damage from any prior global bleaching event. These observations demonstrate that global warming’s widespread damage to coral reefs is accelerating and underscores the threat anthropogenic climate change poses for the irreversible transformation of these essential ecosystems.

Greater functional diversity and redundancy of coral endolithic microbiomes align with lower coral bleaching susceptibility

“…However, with the exception of stimulated endolithic photosynthesis during coral bleaching, the response of the endolithic communities to heat stress in terms of community structure, functional potential, and nutrient cycling is currently unknown. Since 2015, more than 75% of reefs worldwide have been affected by mass bleaching events [36], and nearly half of the coral cover has been lost since the mid-80s on the largest reef system in the world, the iconic Great Barrier Reef [37,38]. Given the escalating impact of marine heatwaves and rising sea surface temperature on coral reef assemblages [39], understanding the microbial processes underpinning coral health, including the overlooked endolithic communities, constitutes an important research priority.…”

Demographic resilience may sustain significant coral populations in a 2°C‐warmer world

“…Six climate models were selected on the grounds of their maturity, and their prowess at capturing El Niño events (Cai et al, 2018), which are an important driver of coral bleaching events (Eakin, 2022;Eakin et al, 2014). Ensemble coral trajectories declined under all RCPs (Figure S1).…”

Algal symbioses with fire corals demonstrate host genotype specificity and niche adaptation at subspecies resolution

“…This symbiosis creates the foundation of coral reef ecosystems and is one of the oldest, most widespread, and ecologically successful known mutualisms found in nature 6 . The rapid pace of environmental change caused by climate warming and other stressors is now posing a serious threat to coral reef ecosystems and has been linked to numerous occurrences of coral bleaching (severe loss of algal symbionts under stressful conditions) 7,8 .…”