Every year, Europe loses around 1,500 km² of nature and cropland to construction — roughly the size of Cyprus over six years. Official EU data underestimates this loss, because the European Environment Agency's methodology often misses smaller developments and changes inside urban green spaces.

The cross-border investigation Green to Grey, published in October 2025, set out to provide a better picture. Initiated by Arena for Journalism in Europe and the Norwegian public broadcaster NRK, and built on a methodology developed by the Norwegian Institute for Nature Research (NINA), the investigation brought together 41 journalists and scientists from 11 countries.

Using a deep-learning land-cover model applied to roughly 185,000 Sentinel-2 satellite images, the team mapped more than 2 million instances of land take across Europe between 2018 and 2023. 40 journalists then manually verified more than 10,000 sample points through a bespoke web app, which scientists used to compute unbiased area estimates with 95% confidence intervals.

The investigation was distributed across 50 media articles in 11 languages and reached more than 3 million people in its first month. Its methodology was later published as a peer-reviewed paper in Nature Communications, with the code and maps made openly available on GitHub.

This session explains how that collaboration worked and gives SciCAR attendees a concrete, replicable template for large, cross-border journalist–scientist collaborations. It offers a practical model for dividing responsibilities, producing robust findings and communicating them effectively to both scientific and public audiences.