The global extent and distribution of forest trees is central to our understanding of the terrestrial biosphere. We provide the first spatially continuous map of forest tree density at a global scale. This map reveals that the global number of trees is approximately 3.04 trillion, an order of magnitude higher than the previous estimate. Of these trees, approximately 1.30 trillion exist in tropical and subtropical forests, with 0.74 trillion in boreal regions and 0.66 trillion in temperate regions. Biome-level trends in tree density demonstrate the importance of climate and topography in controlling local tree densities at finer scales, as well as the overwhelming effect of humans across most of the world. Based on our projected tree densities, we estimate that over 15 billion trees are cut down each year, and the global number of trees has fallen by approximately 46% since the start of human civilization.
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Extended data figures and tables
Extended Data Figures
- Extended Data Figure 1: Histogram of the collected measurements of forest tree density in each biome around the world (n = 429,775). (264 KB)
The red line and the blue dotted lines indicate the mean and median for the collected data, respectively. Data in each biome fitted a negative binomial error structure.
- Extended Data Figure 2: Histogram of the predicted forest tree density values for the locations that density measurements were collected in each biome around the world (n = 429,775). (257 KB)
The red line and the blue dotted lines indicate the mean and median for the collected data, respectively. As our models were based on mean values, the majority of points fall on or close to the mean values in each biome.
- Extended Data Figure 3: Histogram of the total predicted forest tree density values for each pixel within each biome around the world (n = 429,775). (184 KB)
This illustrates the spread of pixels throughout each biome, and highlights that our map accounts for the sampling bias in tree density plots (for example, although we had no zero values in our desert plots, the vast majority of desert pixels contain no trees).
- Extended Data Figure 4: Comparison between approaches to generate the global tree density map. (646 KB)
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.
Extended Data Tables
- Supplementary Table 1 (15 KB)
Summary Table showing the number of plot estimates and total tree numbers (with 95% confidence interval) at the biome and global scale.