Joshua Tree isn't just the name of Southern California's iconic national park, and U2 fans may argue otherwise, but these amazing trees are also much more than just the inspiration for the band's Grammy-winning fifth album. The Joshua tree is actually a spike-leafed evergreen that only grows in the Mojave Desert in the Southwestern U.S. And according to a new study, these majestic trees could become a thing of the past if climate change predictions pan out.
The study, titled Congruence between future distribution models and empirical data for an iconic species at Joshua Tree National Park, was published June 3, 2019, in the journal Ecosphere, and offers insight on almost 4,000 trees in the park. Because Joshua trees can live for up to 300 years, researchers were able to assess where the oldest trees continued to thrive during periods of extreme heat and drought. By comparing the trees' ideal conditions to projections of the park's future landscape, researchers discovered that just 19 percent of the park's Joshua tree habitat would survive after the year 2070.
"This research was meant to assess changes in the communities of plants and animals within Joshua Tree National Park," says the study's lead author, Lynn C. Sweet, Ph.D., a plant ecologist at the Center for Conservation Biology at the University of California, Riverside, in an email interview. "We have been working with NPS [National Park Service] biologists to set up and design the experiment. The immediate goals have been to see if there have been shifts due to changes in climate that have already occurred, and to model what the future might look like for these plants. Ultimately, we want to give the park very specific information about how the communities are changing so that they can manage the natural resources in the park."
To collect the necessary info, Sweet and her team relied on a variety of contributors and technological tools, assessing changes in where new trees are occurring in the park using first-hand, on-the-ground data. "We used community scientists — volunteers — to count the numbers of Joshua trees in certain areas spread across the park," she says. "We measured over 4,000 trees. We also used computer modeling to look at what types of conditions the Joshua tree likes and where those might occur into the future. For that, we used climate data from climatologists, and information (also from citizen scientists via the iNaturalist app) about where the Joshua trees occur. We used these to project on a map where suitable habitat will be at the end of this century."