All maps are wrong, but some are useful: Benchmarking European forest disturbance products using a consistent reference database

Europe’s forests play a critical role as carbon sinks, yet their capacity for climate change mitigation is increasingly threatened by rising disturbances and increasing demand for wood. Reliable data on disturbance rates and trends are thus needed. Several Earth observation-based products have been released in recent years, providing an outstanding source of information on forest change. However, many of these products lack proper quantification of accuracies, rendering rates and trends derived from them uncertain. We address this problem by developing a new database of forest disturbances for Europe, based on consistent manual interpretation of satellite imagery. Using this database, we derive robust annual disturbance rates at both national and regional scales, as well as trends over time. We further compare our sample-based estimates with state-of-the art map-based products, showing significant differences in map accuracies and thus area and trend estimates. We finally provide a framework for incorporating different map products into an ensemble estimate with well quantified uncertainties. Our results underscore the need for consistent, transparent, and independent reference data, and highlight that relying on a single map product might lead to biased conclusions about forest change in Europe.