Résumé
Knowing spatial and temporal patterns of species distribution is paramount to support marine species persistence. While datasets provided by global aggregators are increasingly rich and useful, they suffer from various types of data quality issues that can impact their usage. Using marine mammals as an example, we assessed the quality and information gaps in species distribution data from three major databases: the Global Biodiversity Information Facility (GBIF), the Ocean Biogeographic Information System (OBIS) and the International Union for Conservation of Nature (IUCN) range maps. We analysed marine mammal records from 2015 (n = 1,396,581) and from 2019 (n = 1,904,968), for six types of common quality or usability issues. Results for both OBIS and GBIF indicate that 35 to 55% (depending on the respective database and year) of individual database's records are potential duplicates, fall on land, or miss a data collection date. The positional accuracy of data records varies greatly due to varying precision and rounding of geographic coordinates. However, coordinate precision is specified only in 45% and 70% of records in GBIF and OBIS, respectively. In 2019, only approximately 70% of GBIF and OBIS records are encoded using more than three decimals (i.e. remaining records have a positional accuracy lower than 100 m). We also quantified that only 19% (n = 135,885) and 11% (n = 133,882) of the records in 2015 and 2019, respectively, were common to OBIS and GBIF. Despite the continuous increase in the number of records in both databases, the number of shared records slightly decreased. It is therefore likely that new records added to GBIF and OBIS between 2015 and 2019 come from different data providers. Finally, to identify potential information gaps in marine mammal distributions, we overlaid IUCN range maps and species occurrences from global databases. We found that areas previously identified as hotspots for marine mammals' diversity show some of the highest rates of potential false positives (i.e. species are thought to occur there based on their range map, but no species record exist in either GBIF or OBIS). While global biodiversity databases are key to assess global species distribution patterns, our study points to challenges that can limit data usability in biodiversity research. Improving existing data entry mechanisms, quality control routines, as well as data exchange between aggregators should help make those databases more useful to the community and reduce the risks of misuse of biological data.