Flora

Trees are plants that commonly occur in the world. Their appearance changes based on the biome.

Trees can be cut down using a Chainsaw, which will grant Wood and Leaves. It is profitable to cut down trees with the chainsaw, as it will always grant more resources than what is needed for one Biofuel.

Trees cannot be planted and will never reappear, so with enough dedication, all trees could be removed from the world.

Speculation
As no wooden structures have been seen so far, it is likely only usable as fuel for the Biomass Generator.