Good news! Thanks to combining different counting techniques we now have our most accurate ever count of the number of trees on the planet. The new figure is approximately 3.04 trillion trees. That's a lot of wood and constitutes a 7 fold increase in the previous best estimate. But don't get excited, there aren't 7 times more trees on the earth than there were last week, we've just conducted a better census.
Previously we have used just satellite imagery to count them but this isn't great at estimating density. From hundreds of miles up it isn't easy to see if a green canopy is made up of lots of smaller trees or fewer larger ones. The new technique involved amassing as many ground based surveys as possible, actually getting outside and counting the number of trees in a given area (over 400,000 hectares in total!), and then cross referencing these areas with the satellite imagery. This then allowed the researchers to know for sure what images of a particular nature translated to in reality. They then extrapolated out over the rest of the planet and Bob's your uncle.
Their results are published in this open access paper from Nature. In it they note that the number of trees has decreased by an astonishing 46% since humans came on the scene and that the number is decreasing by about 15 billion trees each year. This new data will hopefully provide more detail for climate change models and also assessments of items like soil erosion, water purification and other functions that trees perform free of charge.
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| I fear bonsais were not included in the survey. Image used with permission |
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