We need to know the density of trees in various environments to understand how many more we can plant. And when you have that, you also know how many trees alre

We need to know the density of trees in various environments to understand how many more we can plant. And when you have that, you also know how many trees already exist. It's also useful to know how many trees have been lost to development, which is closely related to how many currently exist. And all of that is based on knowledge of tree density in various environments.