This can be a useful dataset for training and validating algorithms for estimating tree canopy cover, height, canopy complexity, biomass, etc from high-resolution satellite data (e.g., optical, lidar, microwave).
Just discovered that Berlin has a publicly accessible tree database for all trees within the city.
There are 839,693 trees in the database. You can view the trees on a map with details of every single tree, like the species & dimensions.