Mass coral bleaching has caused widespread reef loss, highlighting the need for a globally coordinated monitoring system. This review analyzes 60 years of bleaching data, drawing from three global databases (1963–2022) and a survey of reef managers and scientists. The findings highlight major gaps in standardization, geographic coverage, and data consistency within monitoring efforts—factors that limit the ability to understand the drivers of bleaching, inform management decisions and track long-term trends to influence global policies.
The authors identified 29 monitoring methods, grouped into three main categories: remote sensing, underwater surveys, and specimen collection. Analysis of the databases shows belt transects, line and point intercept transects, and random surveys made up 92% of observations. Survey results show that practitioners often use different methods than those reported in databases. They reported more frequent use of combined line and point intercept transects, photo quadrats, belt transects, and visual estimates. Tools like photo quadrats and AI-assisted analysis are more recent techniques that are not yet reflected in global datasets.
Monitoring efforts also vary widely in the bleaching metrics used and the scale at which they’re measured—from satellite-derived spectral signatures at the kilometer scale, to in-water surveys of percent coral cover at the MPA scale, to cellular-level assessments. These different metrics make it difficult to compare results across regions or timeframes and to make informed conservation decisions. To address these challenges, the authors provide several key recommendations:
- Improve coordination and standardization by building a global coalition of monitoring organizations (e.g., GCRMN, ICRI) and platforms (e.g., Reef Check, MERMAID, AGRRA) to define key indicators, promote standard methods, facilitate training, enhance communication, and secure long-term funding.
- Expand monitoring capacity and geographic coverage by investing in training, infrastructure, and taxonomic expertise.
- Integrate technologies by combining traditional approaches (e.g., line and point intercept transects) with photo quadrats and AI-assisted image analysis to enhance accuracy and comparability across sites.
- Facilitate data integration through open-access platforms and standardized metrics, formats, and outputs to improve global data sharing and synthesis.
Implications for managers
- Use standardized methods and report the techniques used, the area surveyed, and metrics collected to enable comparisons and trend analysis.
- Store and share data using standardized, accessible systems to ensure information can be integrated with broader monitoring efforts and used to support decision-making.
- Partner with other monitoring programs at the local, regional, and global levels to share resources, training opportunities, and use common data collection practices.
- Combine new survey tools like photo quadrats, drones, and AI-based tools with more established methods like line and point intercept surveys for more reliable, efficient, and useful data.
- Connect monitoring work to global policy goals like the Global Biodiversity Framework to ensure local efforts contribute to broader conservation and climate resilience strategies.
Author: Rivera-Sosa, A, AI. Muñiz-Castillo, B. Charo, G.P. Asner, C.M. Roelfsema, S.D. Donner, B.D. Bambic, A.G. Bonelli, M. Pomeroy, D. Manzello, P. Martin and H.E. Fox
Year: 2025
Frontiers in Marine Science 12: 1-20. doi: 10.3389/fmars.2025.1547870
