Habitat surrogates for plant richness as a tool for rapid biodiversity assessment in urban areas

Abstract Urban ecosystems represent heterogeneous environments with mosaics of natural, semi-natural and man-made habitats, with plenty of vascular plants including native and alien species. In-depth biodiversity research in urban areas might be time- and personnel-consuming. Therefore, we selected six habitat types within 30 towns in Slovakia (Central Europe) to determine whether any urban habitats could serve as a ‘surrogate habitat’ for the total, alien and Red List vascular plant richness of the towns. We found 1054 vascular plant taxa overall; alien and Red List plants comprised 33.9% and 7.3% of all taxa, respectively. The most species-rich habitat was the cemetery (mean number of taxa = 121), while the town centre hosted the lowest mean number of plant taxa (87). The habitat type that best predicted total species richness in the study towns was the floodplain (RMSE ≈ 20 species, RRMSE = 8.5%). In the case of aliens, the number of species in railways and town centres could be used for the rapid estimation of total alien richness in towns (RMSE ≈ 8 species, RRMSE = 10.8%). For Red List species, none of the habitats (including combinations of two habitats) could be recommended for a rapid estimation, as their prediction errors were exceptionally high (RRMSE = 45–62%).