Forest ecology: Three trillion trees

Nature 525, 201–205 (2015)

The planet is home to an order of magnitude more trees than previously thought, reveals a global study of tree density.

Credit: IMAGOSPOT/ISTOCK/THINKSTOCK

Thomas Crowther, of Yale University, and colleagues mapped forest tree density at a global scale, using tree count data from every continent on Earth barring Antarctica, satellite imagery and biome-specific regression models. The total number of trees on the planet amounts to around 3.04 trillion according to their calculations, equivalent to 422 trees per person. The greatest densities are found in the boreal forests of North America, Russia and Scandinavia. But the greatest numbers are found in tropical and subtropical regions, which together harbour the highest proportion of the world's forested land, and over 40% of the world's trees.

Combining their density data with a spatially explicit map of forest cover loss, the researchers estimate that deforestation, forest management, disturbance and land use change are collectively leading to the loss of over 15 billion trees each year. A comparison of their data with estimates of ancient forest cover suggests that since the onset of agriculture the global number of trees has fallen by over 45%.

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Armstrong, A. Forest ecology: Three trillion trees. Nature Plants 1, 15154 (2015). https://doi.org/10.1038/nplants.2015.154

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