Biodiversity is one of Earth’s most precious resources. However, for most places in the world, scientists only have a tiny picture of what this diversity actually is. Researchers at the German Centre for Integrative Biodiversity Research (iDiv) and Martin Luther University Halle-Wittenberg (MLU) have now constructed from scattered data a world map of biodiversity showing numbers of tree species. With the new map, the researchers were able to infer what drives the global distribution of tree species richness. Climate plays a central role; however, the number of species that can be found in a specific region also depends on the spatial scale of the observation, the researchers report in the journal Nature Ecology and Evolution. The new approach could help to improve global conservation.