The bark of different trees has evolved to make best use of the environment in which each species occurs. Scots Pine (Pinus sylvestris) bark offers protection from fire. In prehistoric times, parts of Scotland’s woodlands would have been influenced by fires, which would have occasionally swept through areas of forest. While this may seem devastating, when forests were more extensive, pinewood ecosystems would actually have benefited from such natural disturbance, as it can clear away rank vegetation, leaving a fertile bed on which pine seeds can germinate. Many Scots pines have very characteristic thick protective plates on their bark, and it is thought that in areas more prone to fire the bark may become locally adapted to offer extra protection.
Many trees have chemicals within their bark, which protect against fungal and insect attack. Birch (Betula spp.) bark is high in volatile oils (this is why it’s also great for lighting fires!), and is so waterproof and resistant to decay that tubes of birch bark can still be found on the forest floor after the wood inside has decayed. The bark of Oak (Quercus petraea) is very high in tannins, which are toxic and protect the tree from insects.