A forest is any ecological community that is structurally dominated by tree-sized woody plants. Forests occur anywhere that the climate is suitable in terms of length of the growing season, air and soil temperature, and sufficiency of soil moisture. Forests can be classified into broad types on the basis of their geographic range and dominant types of trees. The most extensive of these types are boreal coniferous, temperate angiosperm, and tropical angiosperm forests. However, there are regional and local variants of all of these kinds of forests. Old-growth tropical rainforests support an enormous diversity of species under relatively benign climatic conditions, and this ecosystem is considered to represent the acme of Earth's ecological development. Within the constraints of their regional climate, temperate and boreal forests also represent peaks of ecological development.

Many countries have developed national schemes for an ecological classification of their forests...