Forestry is a Tier Two technology available after researching Hunting.
Forestry allows you to clear forests, which gives two stars and transforms the forest tile into a field tile.
It also unlocks the Lumber Hut tile improvement, which gives one population to the nearest city.
Forestry expands into Mathematics.
Sawmills also gain 1 level and give +1 population for each adjacent Lumber Hut.
If you are playing as ∑∫ỹriȱŋ, Forestry unlocks the Sanctuary, a building that produces stars. The Sanctuary replaces the Clear Forest ability.