Remote sensing technologies for monitoring coral reef health under climate change

Climate change-driven coral bleaching is the most acute and visible threat to coral reefs, which support biodiversity, coastal protection, and human livelihoods. Yet monitoring remains uneven across space, depth, and time. This review evaluates the performance and limitations of satellite- and UAV-based remote sensing for bleaching detection and outlines pathways toward operational, management-ready monitoring. Using a PRISMA-guided synthesis of 1995-2024 peer-reviewed studies, we compare multispectral platforms (Sentinel-2, Landsat, MODIS) with hyperspectral and UAV systems in terms of spectral sensitivity, spatial resolution, revisit frequency, and validation practices. Sentinel-2 and Landsat enable basin-to regional-scale assessments, while MODIS provides essential thermal context but limited habitat detail. Hyperspectral and UAV approaches can detect early and sublethal bleaching signals but remain underutilized, appearing in fewer than 15 % of studies. Persistent geographic biases-particularly the underrepresentation of Southeast Asia, mesophotic reefs, and high-latitude systems-restrict global understanding, while weak standardization hampers comparability across studies. Multi-sensor fusion of thermal and optical data, coupled with water-column correction and machine learning, substantially improves attribution between heat exposure and benthic change but requires coordinated protocols and robust ground-truthing. Future progress will depend on targeted deployment of UAV and hyperspectral assets, standardized validation, and open, interoperable monitoring pipelines that connect near-real-time thermal alerts with fine-scale benthic diagnostics.