Nils-Petter was commissioned to produce a serie of illustrations about sustainable forestry for Sveaskog, Sweden's largest forest owner. Sveaskog wanted Nils-Petter to depict forest inventory and valuable environments; what trees to leave in a felling; tree zones facing mountains, old pine trees, thick aspen, tree shaped sallow, fire damaged trees, old junipers, tree shaped rowans, dead wood, valuable biotopes like marshlands, trees on rocky land, leafy tree groups, special tree groups and tree zones facing water.