Summary

Forests in Europe are under pressure from logging, forest fires, storms and pests. Rapid insight into where and when disturbances occur is crucial for sustainable forest management and nature conservation policy. Researchers at Wageningen University & Research together with Prof. Dr Martin Herold from the GFZ Helmholtz Centre for Geosciences have demonstrated that disturbances can now be detected in near real time, using a detection system based on radar images from the European Copernicus Sentinel-1 satellite constellation. They have adapted a method already established for tropical regions, using additional data and modelling of temperature and forest type, so that it can now also reliably monitor European forests, which challenge the system with frost as well as regional and seasonal changes in foliage. The study has been published in the journal Remote Sensing of Environment.

Advantage of radar: Seeing through the clouds

Satellite-based optical and radar remote sensing has become a key tool in assessing the extent and severity of forest disturbances. Radar systems such as those in the Sentinel-1 satellite constellation offer decisive advantages: whilst optical systems can only provide images of the Earth in bright conditions and under cloudless skies, radar satellites capture images around the clock and through the clouds. As a result, new images are available every three to six days, with a level of detail in which each pixel corresponds to an area of 10 by 10 metres.

Challenge and new approach: The natural variation in European forests

This approach has already proven effective for monitoring tropical forests. However, the system cannot simply be applied to European forests. This is because, in European forests, factors such as frost and regional and seasonal changes in foliage influence the physical parameters that determine the reflection of radar signals. This can lead to misjudgements when identifying disturbances.

To distinguish between ‘normal’ variations and actual disturbances such as logging, the researchers combined the radar data with satellite-based information on forest type from the Copernicus programme and with modelled temperature data from ERA5-Land, a high-resolution dataset which – based on models and observational data – provides a highly detailed reconstruction of weather and environmental conditions over land. 

A new forest disturbance alert is triggered based on a single observation from the latest Sentinel-1 image. Subsequent observations are used to increase confidence. Low-confidence alerts can be moved to high-confidence after 30 days. The date of the alert is set to the date of the image that first triggered the alert. RADD Europe (Radar for Detecting Deforestation) alerts are operational for 34 countries.

The research team included lead author Sietse van der Woude and colleagues from Wageningen University & Research, as well as Prof. Martin Herold, who heads Section 1.4 “Remote Sensing and Geoinformatics” at the GFZ Helmholtz Centre for Geosciences.

The new approach provides high accuracy and rapid detection

The team demonstrated that the system can now monitor European forests all year round – from snow-covered boreal coniferous forests to dry Mediterranean deciduous forests. To demonstrate the effectiveness of the new approach in detail, they analysed data from various European regions. This showed that the detection system is reliable but also has certain limitations: In over 91% of cases, disturbances reported by the system were found to actually involve logging, forest fires, storm damage or pests. On the other hand, 25% of actual disturbances were not detected; the system sometimes misses parts of natural disturbances with lower intensity, such as forest fires where many trees remain standing. 

New tree canopy cover changes are detected on average within 27 days of the actual moment of occurrence. With an additional retrospective correction method, this delay can even be reduced to an average of one day.

Detection of disturbances throughout the year

The system also provides insight into when disturbances occur throughout the year. This reveals differences between winter harvesting in Northern Europe, spring felling in Central Europe and summer fires in Southern Europe. Another important advantage is that small-scale interventions, such as group felling in Romania, also become visible. 

Support for policy and enforcement

The new warning system provides up-to-date and open source for all European forests. Such detailed information can support policymakers, managers and enforcers in sustainable forest management and nature policy mechanism with up-to date information. For example, it can assist authorities in detecting illegal activities or evolving climate-induced disturbances. Thus, the system enables a faster response to changes in European forests, thereby ensuring better care for one of our most important natural resources.

(Based on the press release from Wageningen University & Research (WUR))
 

Original publication:

Sietse van der Woude, Johannes Reiche, Johannes Balling, Gert-Jan Nabuurs, Frank Sterck, Anne-Juul Welsink, Bart Slagter, Martin Herold, European forest disturbance alerting using Sentinel-1, Remote Sensing of Environment, Volume 337, 2026, 115325,

https://doi.org/10.1016/j.rse.2026.115325
 

Online Data Viewer – the near-real time European forest data are available open source and are regularly updated:

https://wurnrt-raddeurope.projects.earthengine.app/view/radd-europe