Joshua trees have lasted for millennia in the brutal deserts of the southwest.
Their twisted branches and prickly leaves shaped like pompoms have seen Mormon settlers rest in their shade and Native Americans use their roots for dyes.
Because of climate change, however, roughly 80% of the habitat for the famous plants in Joshua Tree National Park might not survive past 2100 — and that’s being optimistic, UC Riverside scientists conclude in a new study.
Researchers at UCR’s Center for Conservation Biology, among other institutes, published the study in June in the journal Ecosphere. It confirms what scientists said years ago in previous studies: the trees’ fate is in the hands of humans.
Beyond that, their findings revealed another startling point.
The habitat, sandwiched between the 10 and 62 freeways in the San Bernardino County desert, is dying already as the park gets warmer and drier.
“If we carry on business as usual, most of the habitat will be wiped out by the end of the century,” said UCR plant ecologist Lynn Sweet, first author of the study.
Today, forests of the trees stretch from Los Angeles County to Utah. They’ve made cameos in thousands of Instagram photos at the national park that was named after them, and may have reminded Mormon settlers of the biblical Joshua outstretching his hands.
But the park’s habitat for the iconic trees may not last.
As summer high temperatures rise and winter lows go even lower because of climate change, the trees will start to die off in park areas where they’ve stood for thousands of years, Sweet said. Instead, Joshua trees that survive will be in higher elevations than usual, she said.
Problems will arise for the trees in those higher spots, where the changing climate will eventually subject them to the same extreme temperatures and dryness they experienced at lower elevations. And when those places get too hard to live in, they’ll have fewer suitable areas in which they can thrive.
In the study’s worst-case scenario, the roughly 160,000 acres across the park that have historically supported Joshua trees could fall to just 37 by 2100. That’s about half the size of Disney California Adventure.
The forecast could ring true if the climate continues to worsen, Sweet said.
“They’re very tough,” she said of the trees. “But, really, getting much drier and hotter could be a problem.”
For many environmentalists, it’s a sobering realization. It’s also far from surprising.
Kathryn Phillips, the director of Sierra Club California, said the findings confirm her belief that humans need to limit air pollution and use of oil, which contribute to climate change.
“When I hear stuff like that, it motivates me. I’m not the kind of person that wants to roll up into a fetal position and cry. I want to take action and fight back,” she said.
Sweet is optimistic that her team’s best-case model will match the future more than its worst-case because of current efforts to control climate change.
Already, several mandates from the state and federal government limit greenhouse gas emissions and have set goals for cleaner energy. And, while Joshua Tree National Park officials can’t stop global temperatures from soaring, they are acting to prevent fires, which can be worse because of climate change.
Crews are cutting down dry grasses fertilized by polluted rain to reduce the risk of wildfires spreading to the trees, said Neil Frakes, the park’s head of vegetation management and an author of the study.
To Chris Clarke, a Joshua Tree resident and California desert program manager with the National Parks Conservation Association, there’s more work to be done.
If Joshua Tree National Park expects to have its famous plants by 2100, “there needs to be large-scale, systemic change in the way we run our societies worldwide,” said Clarke, 59.
“We need to do that yesterday.”
Before the plants join U2’s landmark 1987 album ‘The Joshua Tree‘ in the history books of future generations, Clarke encouraged people to enjoy the unique species while they still can.
But, he added, “by all means, carpool.”
