GLOBAL GREENHOUSE TO ICEHOUSE AND BACK AGAIN: THE ORIGIN AND FUTURE OF THE BOREAL FOREST BIOME
Probable sources for the pinaceous taxa that now characterize boreal latitudes were the evergreen montane coniferous forests of the North American western Cordillera. Taphonomic factors limit the fossil record for such forests, but assemblages such as the Eocene Thunder Mountain (Idaho) and Bull Run (Nevada) floras are excellent analogs of extant boreal communities. In response to post-Eocene global cooling, such forests would have migrated to lower elevations, eventually spreading across high-latitude North America, subsequently reaching Eurasia via the Beringian corridor. Despite its extensive geographic distribution, the Boreal Forest may be the youngest of the major forest biomes.
If anthropogenic global warming results in a significant redistribution of terrestrial vegetation, the history of the Boreal Forest may well be reversed. Unable to survive at high polar latitudes, evergreen conifers might once again become restricted to New World and Old World montane refugia. Given the biogeographic significance of the Boreal Forest biome, such a consequence would represent a profound ecological transformation.