In Siberia, over 3 million hectares of boreal forests are lost annually through logging operations. In many areas, loss of old-growth forests is an issue. Much of the original forestland in the United States has been replaced by agricultural lands, second-growth forests, plantations, and development. In British Columbia, only one of 25 large coastal watersheds has wholly escaped logging. A forest is a natural, self-sustaining community characterized by vertical structure created by the presence of trees.
Trees are large, generally single-stemmed, woody plants.
Forests can exist in many different regions under a wide range of conditions, but all true forests share these physical characteristics. Because a forest is a natural community, no forest is static in time. That is, because forest communities respond to outside, or edaphic, influences, most forests are in a state of constant flux. Depending upon the systems within which forest communities exist, such factors might include rainfall, fire, wind, glaciation, seismic activity, flooding, animal activity, insulation, and so on. At any time, a forest is the collection of past responses to edaphic influences and internal competitive interactions.