Recognition and completeness metrics from iNaturalist and GBIF can inform future citizen science and research projects: a case study on arthropods in Namibia

Arthropods are the most diverse animal phylum and play crucial roles in ecosystem functioning through their contributions to ecosystem processes. Accurate knowledge about their distribution and diversity is essential for effective ecosystem management and biodiversity conservation. Public biodiversity databases and citizen science records could contribute to our understanding of arthropod diversity. To test this assumption, we extracted arthropod observations in Namibia from iNaturalist (iNat) and the Global Biodiversity Information Facility (GBIF) and compared these data to the records in the Namibian Biodiversity Database (NBD). We assessed the proportion of observations identified to species level in each arthropod order in iNat and GBIF (“recognition” metric) and compared the number of species from the two biodiversity networks (iNat and GBIF) to the known species richness in each arthropod order in NBD (“completeness” metric). Only 54.4% of iNat and 63.1% of GBIF arthropod observations in Namibia are recorded at species level. Scorpions (Scorpiones) and dragonflies (Odonata) are the most recognised orders in both GBIF and iNat, with high completeness rates (> 60%). However, overall recognition and completeness for all arthropod orders were generally below 50% in both databases. The high recognition and completeness for certain orders could be attributed to species traits that make them recognizable (e.g. large body size, colouration), a low species richness and the taxonomic familiarity of the public. While global biodiversity networks provide valuable data, regional or national databases like NBD remain essential for comprehensive biodiversity understanding. Global biodiversity networks provide insights into public perception and the suitability of taxonomic groups for citizen-involved biodiversity projects.