Calling long distance

above-ground biomass and a 20-fold increase in plant cover by Artemesia frigida, a common shrubby plant of some North American and Asian grasslands. This carbon dioxide induced enhancement of plant growth, among the highest so far reported, provides evidence from a native grassland that rising carbon dioxide levels since the onset of industrial times may have been contributing to the observed shrubland expansions over the past 200 years. “Encroachment of shrubs into grasslands is an important problem facing rangeland managers and ranchers; this process replaces grasses, the preferred forage of domestic livestock, with species that are unsuitable for domestic grazing,” the authors conclude. And ecologists have little to cheer too. This species is considered one of the least desirable for wildlife, used only occasionally by pronghorn and elk. It is known only to be an important food source for sage grouse. The researchers, working on the western edge of the Great Plains, believe more work is now needed to see whether other parts of these grasslands may be susceptible to similar changes. Vulnerable: A new study finds the grass species in a Colorado plot threatened by woody plants under conditions of raised atmospheric carbon dioxide. (Photograph: © David Crockett/Alamy.) Calling long distance