Imagine you’re listening to U2’s fifth studio album, The Joshua Tree—you know, the one that turned the Irish rockers into megastars and made “I Still Haven’t Found What I’m Looking For” a radio staple? Now imagine going to California’s Joshua Tree National Park and not being able to find any of the namesake trees. It sounds crazy, but thanks to climate change, the iconic trees are dying off.
The gnarled yucca is native to the American Southwest, so it’s used to thriving in a dry environment. But even the hardiest of species can’t withstand the ravages of excessive heat and widespread drought that have been common in the region over the past decade.
Scientists report that younger Joshua trees are now rarely seen in the lower elevations of the park, and older trees are also dying. Plant ecologist Ken Cole told the Desert Sun that he first noticed something was going on with Joshua trees in the region in 2003, during a visit to the Lake Mead National Recreation Area a few hours to the northeast.
"I noticed that a large number of the trees were dead and half of them were kind of slumping over like they were under severe stress," Cole told the newspaper. "Then I went and I looked back and I realized that the previous year, 2002, it had only rained a tenth of an inch or so there.” The following year was also, said Cole, “an extremely warm year but also pretty dry, so that was very stressful for these particular Joshua trees I was looking at, and then I began to realize, 'Holy cow, something is going on here.' "
Cole published a study in 2011 that predicted that a drier, hotter habitat would slash the number of Joshua trees by one-third over the next 60 years. Other scientists have predicted that climate change will kill 90 percent of the park’s Joshua trees by 2100. Although the region is already a desert, even gradual temperature changes during the day, as well as hotter temperatures at night, are disrupting the ecological balance of the area. Joshua trees are only pollinated by the yucca moth, which, in turn, produces larvae that only eat the plant’s seeds. A Nature Conservancy study has found that the moth can’t survive in warmer temperatures, which spells doom for Joshua trees.
Scientists and park officials are teaming up to research the impact of climate change on the national park’s trees and animals. Documenting the changes may provide insights that can save the wildlife and plants. The research team has already discovered that at higher elevations, which are moister and cooler, the trees seem to be surviving. But unless efforts to slow and reverse climate change are successful, visitors tracing U2’s journey through the Southwest and trying to re-create the famous album cover image will soon be out luck.