Harmonising digitised herbarium data to enhance biodiversity knowledge: Major steps towards an updated checklist for the flora of Greenland

Societal Impact Statement: Herbaria worldwide hold centuries of plant data that are key to understanding and protecting biodiversity; however, even with increased digital access, differences in plant naming systems make it difficult to compare records. We developed a semi-automated workflow that standardises species names and organises herbaria records from multiple institutions into a single, curated digital collection. Applying our workflow to the digitised flora of Greenland, we improved the accuracy of diversity estimates and highlighted tentative species previously unrecognised in Greenland. Our resulting open-access resource opens new doors for large-scale studies on Arctic plant diversity over space and time. Summary: International efforts in digitisation and online data sharing of herbarium specimens are revolutionising our ability to obtain big data from herbarium collections. The herbaria of the future will be global, digitally interlinked, open-access resources that will stimulate large-scale and novel science to directly address our current biodiversity and climate crises. However, taxonomic changes and errors can result in inconsistencies when amalgamating specimen metadata, that compromise the assignment of occurrence records to correct species and the subsequent interpretation of patterns in biodiversity. We present a novel workflow to mass-curate digital specimens. By employing existing digital taxonomic backbones, we aggregate specimen names by their accepted name and flag remaining cases for manual review. We then validate names using site-specific floras, balancing automation with taxonomic expert-based curation. Applying our workflow to the vascular plants of Greenland, we harmonised 177,138 digitised herbarium specimens and observations from 88 data providers from the Global Biodiversity Information Facility (GBIF). The harmonised metacollection of the Greenland flora contains 753 plant species. Our workflow increases the number of species known from Greenland compared to other currently available species checklists and increases the mean number of occurrences per accepted name by 48. Our workflow illustrates the nomenclature data integration required to create a global, universally accessible digital herbarium and shows how previous obstacles to database curation can be overcome through a combination of automation and expert curation. For the Greenland flora, our approach provides a new species list and a curated metacollection of occurrence data.