Ecosystem extent mapping in a global monitoring context.

The vital role of ecosystems in maintaining biosphere stability is now recognized globally. Updates in policy frameworks on biodiversity and environmental decline include information on ecosystem extent (EE) as a core assessment indicator, e.g., the Global Biodiversity Framework indicator A2 'Extent of natural ecosystems'. The recently proposed System of Environmental-Economic Accounting - Ecosystem Accounting requires EE as the first pillar for assessing ecosystem condition and, ultimately, ecosystem services. Detailed and up-to-date information on ecosystem characteristics is increasingly achievable due to the unprecedented availability of Earth observation data, combined with advances in geospatial data analysis and high-performance computing, building on a long-established tradition of surface monitoring. However, consistent mapping and delineation of EE remains a challenge. This research aims to identify the role of EE mapping data in nature protection, environmental degradation, and climate agendas, and define components of the usability of geospatial data products as operational solutions. For that, we analyzed global and regional policy frameworks and corporate reporting standards to determine EE-related data needs, alongside bottlenecks shaped by domain-specific challenges, such as thematic complexity of ecosystem definitions, high costs of in-situ monitoring, and demands of data processing workflows to capture dynamic and complex entities. Finally, we translated these findings into a checklist to design policy- and reporting-ready products, covering relevance, thematic coherence, reliability of mapping outputs defined by validation and uncertainty quantification, and transparency of data and methods contributing to the achievement of shared policy targets.