A study in Functional Ecology offers evidence that desert ecosystems, long perceived as the most resilient to climate change, may be hitting their limits. Researchers at the University of California Riverside found that rising temperatures and protracted drought have driven piñon pines and juniper trees to seek refuge at higher elevations in the deserts north of Palm Springs. In the place of these slow-growing, iconic forests is rising an empire of weeds.  That is part of a wholesale transition in arid landscapes caused by the burning of fossil fuels, the scientists said. … While the piñon pines and junipers are often seen as hardier, they nonetheless depend on ready access to underground water. That’s in ever-shorter supply thanks to the West’s long drought, though this year’s record rainfall has provided a brief respite.