The boreal forest is restricted to the northern hemisphere. It is circumpolar in distribution, as are many of the species which comprise it and even more of the genera. In general, plants have different species represented on North America and Eurasia; the mammals of both continents tend to be conspecific. There are latitudinal zones within the forest. Running north to south, one finds: (1) the tundra/taiga ecotone; (2) an open coniferous forest (the section most properly called taiga); (3) the characteristic closed-canopy needleleaf evergreen boreal forest; and (4) a mixed needleleaf evergreen-broadleaf deciduous forest, the ecotone with the temperate broadleaf deciduous forest.
The boreal region contains large parks and nature reserves, and parts of it such as Alaska include some of the most extensive areas of legislatively protected land in the world. The world boreal forest hosts a huge influx of migratory birds that breed in the summer and then migrate south during the long winter.