• This paper seeks to determine whether N-deposition has a negative impact on the species richness of calcareous grasslands at a European wide scale. • 100 calcareous grasslands across the Atlantic region of Europe were sampled in one season. Species composition and richness of vegetation communities were compared to some key environmental drivers (climate and N deposition) indirectly estimated via surrogates (latitude, longitude, N concentration in bryophyte tissue). • There are marked differences in species composition across the calcareous grasslands of the Atlantic biogeographic zone within Europe. Contrasts in mean species richness between regions are also detectable at a European wide scale. These natural gradients may mask any footprint of N deposition on vegetation at a European-wide scale. • For grasslands located along the western range of distribution, there are indications of a decline in species richness as N concentration in moss increases. This suggests that N deposition may be reducing biodiversity in calcareous grasslands at a wide scale, but that this impact can only be detected at the regional, rather than cross-European, level. • Further research is needed to investigate the impact of N deposition on calcareous grasslands, particularly through the direct assessment of potential drivers as well as the characterisation of variations in species pools at the European scale
