Grassland Loss and Ecological Risks in Bulgaria: A Multi-Source Remote-Sensing Assessment

Ground-mounted solar parks create new land-use pressures in Europe, particularly where they compete with semi-natural grasslands. In Bulgaria, this remains poorly quantified. We combined national agricultural statistics, Copernicus Grassland Change (GRAC) maps, six Annex I grassland habitats and 704 mapped solar sites. The national estimate of agricultural permanent grassland was 720,339 ha (42.3%) lower in 2025 than in 2010. More than half of this difference followed the 2025 control of survey points and is not an equivalent loss of the semi-natural habitat. Within 198,095.77 ha of the mapped habitat, GRAC classified 2824.88 ha as grassland loss in 2018–2024. A stratified sample of 250 locations, interpreted blind from Sentinel-2 data, confirmed 37% of this area (1056.64 ha), mostly ploughing to arable land. It put total grassland loss at 1313 ha, or 3531 ha if a single influential reference location is classified as loss; neither value is a definitive estimate of habitat loss. Solar sites (4675.13 ha) overlapped 78.98 ha of the habitats, including a 2019–2020 plant extension on 20.16 ha. In the 2016–2018 baseline land cover, 34.81% of the solar-site area was grassland or shrubland; construction dates of 17 large sites gave conditional scenarios of 560.62–1309.08 ha of potential conversion. Solar development should prioritise already modified land and avoid species-rich grasslands.