A huge shift in tree species is taking place across the western United States and Canada as global warming, drought, insect infestations, and fire are driving certain species out of some regions and allowing new species to take their place. Using remote sensing data, U.S and Canadian scientists analyzed the condition of 15 coniferous tree species in 34 different "eco-regions." The study found that once-common tree species, such as lodgepole pine and Engelmann spruce, are being replaced by species that can survive in warmer, drier conditions, such as ponderosa pine and Douglas fir. The most intense shifts are occurring in the northern and southern extremes of western North America. In central California, for example, half of the species now present are not expected to survive future climate conditions, with temperatures expected to rise by 5 to 9 degrees F this century, according to the study, published in the journals Ecological Modelling and Remote Sensing of Environment. Already, more than 70,000 square miles of forest in the western U.S. and Canada have been destroyed by outbreaks of beetles that thrive in warmer temperatures. "Some of these changes are already happening pretty fast and in some huge areas," said lead author Richard Waring of Oregon State University. "The forests of our future are going to look quite different."