A tree is defined as a woody perennial plant, having a single elongated trunk with several branches spreading at a certain height which give shape to its canopy (crown). The trunk usually has a minimum diameter of 10 cm at chest height. The leaves may be deciduous (falling seasonally) or evergreen. Young trees with a trunk measuring less than 10 cm in diameter are called saplings. Most tree species are flowering plants or conifers. They are distributed throughout the world, with the highest diversity in rainforests of the tropical regions. The majority of tree species belong to the families Dipterocarpaceae (Dipterocarps), Fagaceae (Beech family) and Lauraceae (Laurel family). Trees are used to produce a variety of our needs, including timber, furniture, paper and medicine. They also play an important role in preserving the environment (ecosystems) by preventing land degradation and erosion, producing oxygen and absorbing carbon dioxide and managing microclimates.