Synthetic aperture radar for a changing planet: A 25-year global synthesis in hazard assessment, urban development, and ecological applications

The increasing frequency and intensity of natural disasters, rapid urbanization, and accelerating ecological degradation underscore the urgent need for robust monitoring tools. Over the past two and a half decades, Synthetic Aperture Radar (SAR) technology has transformed the landscape of remote sensing, offering unique capabilities for all-weather, day-and-night imaging. SAR applications have expanded dramatically into critical domains such as hazard assessment, urban development, and ecological management. Despite significant progress, fragmented knowledge, uneven adoption across geographies, and several technical, methodological, and application-specific challenges continue to constrain its full potential. This systematic review synthesizes the global research trends, technological evolution, application domains, and persisting bottlenecks in SAR utilization across three key thematic areas: hazard assessment, urban development, and ecological management over the past 25 years (2000–2024), supported by a comprehensive bibliometric analysis of 11,201 peer-reviewed publications indexed in the Scopus database. Unlike previous reviews that often focus on narrow applications or specific sensor types, this review offers a holistic, cross-sectoral, and longitudinal perspective, identifying emerging trends, underexplored geographies, and growing intersections with novel computational frameworks. The study employed a systematic review protocol based on PRISMA guidelines, combined with bibliometric techniques using VOSviewer and Bibliometrix (R-package). The articles were retrieved using a well-defined keyword query related to SAR, hazards, urban studies, and ecosystems. Analyses included publication trends, co-authorship networks, keyword co-occurrence, source impact, and thematic evolution. Cluster analysis identified four major research themes and three temporal development phases. Results indicate that publications increased nearly tenfold from 2000 to 2024, with a peak after 2015 due to the launch of Sentinel-1 and the rise of open data. Major contributing countries include China, USA, Italy, Germany, and India, with strong international collaborations. Interferometric SAR (InSAR) and Polarimetric SAR (PolSAR) dominated hazard and urban studies, while multi-temporal-based approaches emerged in ecological monitoring. Notably, integration with AI and cloud-based geospatial platforms remains limited (<15 % of publications). Urban development applications, especially subsidence and infrastructure monitoring, show the fastest growth, while ecological applications lag, indicating a critical research gap. Furthermore, this review underscores that while SAR has made substantial strides, methodological integration, capacity building in the Global South, and translation into policy-oriented tools remain key challenges. The findings advocate for multi-sensor synergy, open-data initiatives, and interdisciplinary collaborations as pathways to expand SAR's impact. Overall, this review serves as a reference point for researchers, practitioners, and policymakers aiming to harness SAR for sustainable development and disaster resilience in the coming decades. • SAR transformed hazard, urban, and eco studies with 25 years of innovation & insight. • Global SAR research increased 10× since 2000 and Sentinel-1 boosted open-data use post-2015. • InSAR and PolSAR led hazard & urban apps; eco-monitoring lags, urging new focus. • AI and cloud integration in SAR is under 15 %-a key frontier for future expansion. • Review calls for SAR-policy links, Global South inclusion, and multi-sensor synergy.