Extended Data Figure 4: Comparison between approaches to generate the global tree density map.

The initial map was generated using 14 biome-level models (biomes delineated by The Nature Conservancy http://www.nature.org) to account for broad-scale variations in terrestrial vegetation types. With several thousand plot-level density measurements in most biomes, this approach provided highly accurate estimates at the global scale. However, to improve precision at the local scale, we also generated a map using ecoregion-scale models. Separate models were generated within each of 813 global ecoregions (also delineated by The Nature Conservancy to reflect smaller-scale vegetation types) using exactly the same statistical approach (see Methods). The same 429,775 data points were used to construct each map. Biome-level and ecoregion-level maps provide total tree estimates of 3.041 and 3.253 trillion trees, respectively.