Citizen science data as a tool for monitoring moss diversity in Poland: potential and limitations

In this study, the potential and limitations of iNaturalist for monitoring mosses in Poland (2019–2025) were assessed using 17,451 verified “Research Grade” records. Rarefaction enabled diversity pattern analysis while accounting for sampling effort differences. Observational activity peaked in early-spring (March) and autumn (October). Analysis revealed extreme asymmetry in research effort ( G users = 0.89): the 12 most active users contributed 65.5% of national records, creating a “super-user effect.” Rarefaction corrected this bias, identifying the Pomeranian Voivodeship as having the highest standardized diversity ( S rar = 80.9). Citizen science effectively supports specific moss monitoring aspects. Observers documented 151 unique records of the alien moss Campylopus introflexus , representing over 60% of sites recorded during 30 years of traditional floristic research. Despite the “microscope barrier” restricting the database largely to visually identifiable bryophytes (e.g., reducing nearly the entire genus Hypnum to H . cupressiforme ; G taxa = 0.76), iNaturalist serves as a crucial early-warning system. Ultimately, large-scale citizen scientists datasets provide valuable guidance for identifying priority areas for future bryological research.