Assessing the biodiversity value of wet grasslands: can selected plant and insect taxa be used as rapid indicators of species richness at a local scale?

Sixty percent of the land surface of the Republic of Ireland is farmland of which up to 12 % is estimated to sustain high species richness. Given that this farmland is predominantly pasture-based, the ecological status of semi-natural grasslands is particularly important for biodiversity. Recent studies indicate that those grasslands with high nature value (HNV) in the north-west of Ireland are wet grasslands. We investigated seven taxa as potential bioindicators of species richness of wet grassland habitats and examined how this information could be used in rapid assessment methodologies to identify areas of HNV. Grasses, sedges, rushes, ground beetles (Coleoptera) and marsh flies (Diptera) were identified to species and Diptera to parataxonomic units. Sedges was the most significantly correlated taxon with overall species richness of the remaining taxa. In addition, ten combinations of taxa revealed significant positive correlations with the remaining species richness of which sedges and carabids combined showed the strongest correlation. Our data indicate the appropriateness of using more than one taxon in rigorous studies to reflect the overall species richness of wet grasslands. Nevertheless, the use of a single taxon or a combination of two taxa has a useful role to play in the rapid identification, protection and future monitoring of species-rich wet grasslands where taxonomic and financial resources for rigorous studies are limited. We discuss this in the context of agri-environmental schemes and HNV farmland identification.