A new Colorado State University study of the interior U.S. West has found that tree ranges are generally contracting in response to climate change but not expanding into cooler, wetter climates – suggesting that forests are not regenerating fast enough to keep pace with climate change, wildfire, insects and disease. As the climate becomes too warm for trees in certain places, tree ranges have been expected to shift toward more ideal conditions. The study analyzed national forest inventory data for more than 25,000 plots in the U.S. West, excluding coastal states, and found that trees were not regenerating in the hottest portions of their ranges – an expected outcome. More surprising to the researchers was that most of the 15 common tree species studied were not gaining any ground in areas where conditions were more favourable, indicating that most tree species likely will not be able to move to more accommodating climates without assistance.