Tropical islands quick data gap analysis guided by coral reef geomorphological maps

•Knowledge gaps need to be identified for conservation and management.•A consistent metrics is needed to guide a gap analysis.•A quick spatial approach based on mapped geomorphological richness is presented.•A gap analysis is conducted for Solomon Island. A gap analysis is the initial step towards the identification of areas where data are needed. However, often, data coverage cannot be assessed against a reference that objectively guides the identification of both gaps and priority areas for data acquisition. Here, we describe a quick, effective and reproducible spatial data gap analysis approach based on the relationship between location of available metadata and coral reef geomorphological richness. In Solomon Islands, we identified gaps defined by high richness and low biological data coverage. We collected metadata only, to avoid dealing with data ownership, availability, and formats, and to be able to identify gaps in less than two months. This fast method does not replace quantitative and comprehensive gap analysis, but provides effective identification of areas of high natural value and limited knowledge. The method is widely applicable and particularly invaluable for large and complex domains such as the Coral Triangle.