Ponds in quarries have a higher plant species richness than those in the surrounding landscape

Habitat loss is one of the main drivers of the current global biodiversity crisis, with freshwater ecosystems among those that suffer most. The aim of this study was to compare the environmental conditions and assemblages of semi-aquatic and aquatic plants (vascular plants, mosses, stoneworts) of 15 randomly selected ponds in limestone quarries with those of 15 control ponds in the surrounding landscape. Our study revealed clear differences in habitat quality and plant species composition between quarry and control ponds. The number of all and threatened species was for both vascular plants and mosses higher in quarry than in control ponds. Moreover, threatened moss species were even restricted to quarry ponds, and stoneworts generally only occurred in this type of pond. A higher habitat quality was the key for the increased species richness in quarry ponds compared to control ponds. Particularly, sunlit early-successional stages, a heterogeneous submerged and a large semi-aquatic zone accounted for the higher number of plant species in quarry ponds. Across the 30 studied ponds, sunshine duration and pond diversity were the most important predictors of species richness, followed by the cover of the semi-aquatic zone. All three had a positive effect. Backfilling, afforestation or flooding of quarries after the cessation of mining should generally be avoided. In times of climate change, it is recommended to create a variety of water bodies, including both temporary and permanent ones, within quarries. Where thick topsoil layers and woody plants may establish, they should be removed locally.