Since the 1950s, most of the acid grassland in Wales has been subjected to extended periods of intensive sheep grazing, though exceptional examples of the habitat persist at Breidden Hill and Stanner Rocks, The years of intensive grazing pressure caused high levels of eutrophication that have since been exacerbated by increasing levels of atmospheric nitrogen deposition. The impact of these pressures on the habitat has been devastating, with vast areas of species-poor acid grassland forming landscapes virtually devoid of biodiversity interest, particularly in the Welsh uplands.