Why do trees have bark?
The answer to this seemingly simple question is quite fascinating. Trees have bark for the same reason that we have skin, that is, for protection. Bark serves mainly as a protective cover for the cambium, the thin layer of living cells located beneath it. Cambium cannot be seen with the naked eye. It plays a vital role, though, since it is the living part of the tree. Indeed, this layer of cells enables the tree to grow and to produce wood, roots, leaves and so on.
Bark protects the tree from mechanical injury, the cold, the sun’s rays and above all pathogens. When a tree’s bark becomes damaged, this provides a point of entry for a wide variety of pathogens (diseases, fungi, etc). Similarly, when we cut ourselves, the tissues involved become exposed to the air and are at risk of becoming infected.
Another key function of the bark is to allow the tree to breathe. Just as our skin aids in our respiration, a tree’s respiration occurs partly through the bark, which allows gaseous exchanges to take place between the living cells of the cambium and the outside environment.
Meh, for protection and respiration I guess, like our skin!