Homogenisation of Vegetation in Irish Semi-Natural Grasslands

Grasslands represent an important source of vegetative diversity and provide a range of important ecosystem services. Semi-natural grasslands in Europe face a variety of threats due to changing management practices and other anthropogenic pressures. This study investigates vegetative changes in 12 semi-natural grassland sites in Ireland over an approximately 15-year period. Sites for three habitat types (GS1-dry calcareous & neutral grassland, GS3-dry-humid acid grassland and GS4-wet grassland) were selected from the 2007-2012 Irish Semi-natural Grassland Survey and resurveyed in 2023. The resurveyed sites showed a minor shift in vegetative composition in terms of species richness, but non-metric multidimensional scaling suggests that the grasslands are increasingly homogenous with habitat types having become less distinct. While both species losses and gains were observed, almost half of the forb species decreased in frequency, and some of the rarer species were lost. This raises concerns about the mid- and long-term diversity of Irish semi-natural grasslands and suggests that careful management aimed at protecting diversity is required.