Despite efforts by researchers worldwide to assess the biodiversity of plant groups, many
locations on Earth remain poorly surveyed, resulting in inadequate or biased knowledge. Robust estimates of
inventory completeness could help alleviate the problem. This study aimed to identify areas representing
gaps in current knowledge of African palms, with a focus on Benin (West Africa). We assessed the
completeness of knowledge of African palms, targeting geographic distance and climatic difference from
well-known sites. Data derived from intensive fieldwork were combined with independent data available
online. Inventory completeness indices were calculated and coupled with other criteria. Results showed a
high overall value for inventory completeness, as well as an even distribution of well-known areas across the
country. However, poorly-known areas were identified, which were in remote locations with low
accessibility. This study illustrates how biodiversity survey and inventory efforts can be guided by existing
knowledge. We strongly recommend the combination of digital accessible knowledge and fieldwork, coupled
with expert knowledge, to obtain a better picture of inventory completeness in tropical ecosystems.