Marine biodiversity indicators and online data knowledge systems

Nazli Demirel , Alice C. Hughes , David K Barnes, Patricia Miloslavich, Frank E. Muller-Karger, Ana Lara-Lopez, Ina H Ahlquist, Clive R. McMahon, Charlie Taylor, Alena Cierna, Andrew Szopa-Comley, Frances Davis, Chris McOwen, Katherine Richardson, Ward Appeltans, Mary S Wisz, Neil Burgess

Coastal marine ecosystems and biodiversity are changing rapidly under climate forcing, resource use, pollution and habitat modification. Monitoring these changes, and tracking progress across policy targets, remain constrained by uneven data coverage, fragmented observing networks and inconsistent measurement practices. International policy frameworks, most prominently the Kunming-Montreal Global Biodiversity Framework, alongside Sustainable Development Goal 14 and Regional Seas Agreements, rely on structured indicators to track biodiversity state, pressures, change and management outcomes. However, how well existing indicators align with current monitoring needs, data readiness, analytical maturity and recurring assessment pipelines has not been evaluated systematically. This review compiled and synthesised 145 operational marine biodiversity indicators and examined 223 marine-relevant online knowledge systems that were active and accessible in December 2025. Indicators were classified by analytical role within a state, pressure, response, benefit model, and assessed against their data sources, calculation transparency, update frequency and assessment applicability across depth zones and regions. Indicators describing biodiversity state and spatial pressure composites dominate current reporting and assessment use, particularly for coastal habitats and species-population trends. Fisheries sustainability indicators are comparatively well represented, while indicators tracking responses and biodiversity-linked benefits remain less mature, less standardised across measurement pipelines and less developed for offshore and areas beyond national jurisdiction. The current indicator overview shows expanding analytical capacity, but routine indicator production pipelines and integration of measured biological responses into recurring assessments remain limited relative to pressure mapping and species-level status reporting. The next phase of marine monitoring will likely be defined by recurring analytical production of indicators, greater comparability of measurements and stronger integration of observed biological patterns into routine assessment and policy tracking. Further development of indicators that can support management of pressures at a sector-level to support environmental impact assessment and area-based management or zoning of human activities remains a key direction for future analytical progress.