Very large, old trees frequently develop a hollow centre, a favourite breeding and roosting place for bats. When dead, their rotting wood is a source of food for insects and their predators. A widely-used building material, its strength and lightness often gives it the advantage over concrete and steel. Modern buildings still require timber in roof construction. Timber is used in furniture manufacture, and for various other products ranging from tool handles and sporting equipment to matchsticks.
Pulped wood is used to make paper.
Wood was our first fuel, and is still the main energy source for many people. Sawdust and offcuts are an important fuel in industry, and may be processed to produce alcohol and chemicals. Bark of some trees provides cork and can also be made into simple cord - the main building material of half the world's people. However the main importance of bark is as a source of chemicals and medicines. Tannin, derived from wattle bark, is the basis of the leather tanning industry.