Why does the pine tree have a thick bark?

Bark is the outer layer of the living tissue of the tree. As the living layer grows it pushes the bark layer to the outside, which stretches and cracks the bark.

Bark protects the tree from things that would harm the living tissue of the tree. Dangers include pests such as beetles and termites, and the heat from fires.

Bark also slows the evaporation from the living tissues that would make the sap too thick to travel down to the roots.

Without bark, many trees could not survive in the hot, cold, pest infested areas that they live in.