Environmental drivers of the decline of the fen orchid, Liparis loeselii

Background Liparis loeselii is a rare and declining orchid species restricted to rich fens in the Northern Hemisphere. Habitat destruction, eutrophication, drainage and scrub encroachment have been suggested as reasons for the decline. However, which factors are most important is not well understood. Aims Based on vegetation and environmental properties from extant, potential and historical L. loeselii sites, we i) developed habitat suitability models from either Ellenberg Indicator Values or field-measured environmental properties, and ii) identified the primary reasons for the observed decline of L. loeselii . Results Nutrient status was the most important predictor for L. loeselii occurrence, followed by hydrology proxies (Ellenberg reaction and Ellenberg moisture). Vegetation height and Ellenberg light were of minor importance. Conclusion Effect partitioning based on sites, from which L. loeselii has gone locally extinct, pinpointed eutrophication and drainage to be the most likely primary drivers of the species’ demise. Phosphorus limitation induced by discharge of Calcium-rich groundwater seems to be crucial for L. loeselii to sustain populations in landscapes dominated by intensive agricultural.