Three ecoregions comprise the natural environment of Massachusetts. Atlantic coastal pine barrens occur on Cape Cod, Nantucket, and Martha's Vineyard. These are fire-prone temperate coniferous forests growing on the sandy soils of the coastal plain. The other two ecoregions are temperate broadleaf and mixed forests. Across most of the state, including eastern Massachusetts, south central Massachusetts, and the Connecticut River Valley, the Northeastern coastal forests are a mix of hardwood deciduous oak, maple, beech, hickory and coniferous pine trees. In the Berkshires and north central Massachusetts, the more boreal New England-Acadian forests prevail. These consists mainly of coniferous spruce and hemlock, occasional pine, and deciduous birch trees. Roughly since the Civil War, farms have reverted to woodland. Lumbering activity has decreased in recent decades, so the more undisturbed forests have reclaimed some characteristics of old growth.