There are a lot of trees on this planet. But how many trees there actually are is still kind of fuzzy, because the estimates are based on satellite imagery. It's hard to gauge density. Research by T. W. Crowther et al., recently published in Nature, used on-the-ground sampling to estimate more accurately.
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 1.39 trillion exist in tropical and subtropical forests, with 0.74 trillion in boreal regions and 0.61 trillion in temperate regions.