>>227460Scientists say that before Poland came to existence around 1000 most of the land was actually broad-leaved trees, but then we started to cut them and around XIX century most of it were fields. Then German army in the ww1 came and cut around 2 trillon cubic meters of trees and they planted pine trees and now most of forests are made of pines, sometimes birches. Also most of woods are on poor soils, so there trees grow there more easily.
Although it's still better than Iceland where woods are sparse and trees are like 3 times shorter.