Secondary forest is a woodland area which has re-grown after a major disturbance such as fire, insect infestation, timber harvest or wind throw, and a long enough period has passed so that the effects of the disturbance are no longer evident. It is distinguished from an old growth or primeval forests, which have not undergone such disruptions, as well as third growth forests that result from severe disruptions in second growth forests. Depending on the forest, the regeneration may take anywhere from a century to several millennia.