VOGUE — In a wilderness area at the northwest corner of Joshua Tree National Park, ecologist Lynn Sweet treks across the high desert as raucous pinyon jays swoop overhead. She navigates carefully across the landscape of blackbrush and fragrant junipers to inspect the stump of a Joshua tree. Much of the tree’s trunk, branches, and dagger-shaped leaves are sprawled across the desert floor—most likely the casualty of a gust of wind that snapped it like a toothpick.
The tree was one of thousands that Dr. Sweet and her team examined in a recent study that predicted a worrisome future for the iconic western Joshua tree, Yucca brevifolia, within the national park due to climate change. The tree was less than 25% alive during Dr. Sweet and her team’s last recording. Now, the tree is dead.
Dr. Sweet’s study published in Ecosphere in 2019 suggested that if greenhouse gas emission rates continue “business as usual,” the species’ habitat will shrink by 99.98% by the end of the century, almost completely erasing Joshua trees from the park. The study’s most optimistic model predicts the species’ range in the park will decrease by just over 80%. The small percentage of trees remaining are predicted to migrate to higher elevations of the park, sheltering in refugia, areas where the trees are buffered from unfavorable conditions catalyzed by climate change.
“Climate change is like a flash flood,” Dr. Sweet says. “Joshua trees thrive on the long broad plateaus the park is famous for, but outrunning the wave of warming temperatures of climate change in these valleys is much more difficult than migrating a short distance uphill.” Dr. Sweet points far in the distance at the high mountains where the predicted remaining habitat for the trees would persist by the end of the century. Smaller, rugged specimens of the plant roost on the rocky hillsides like ravens.
When Dr. Sweet’s study was published in mid-2019, it sent a quake across the national news cycle as many grappled to understand what the park would look like in 80 years without its namesake tree that has inhabited the wide plains and rocky peaks of the region for over two million years. As a keystone species, countless other plants and animals depend on the Joshua trees for their own survival, including species like yucca moths and desert night lizards. Because of this, the tree's mass disappearance may drastically alter the park’s ecosystem. “Since it’s such a short time period, we don’t know exactly what the park is going to look like at the end of the century,” Dr. Sweet says, explaining that a variety of factors will determine whether older trees persist but are unable to make new ones or, worst case scenario—the trees are almost completely eliminated from the park.
In 2019, Joshua Tree National Park set a new attendance record, drawing nearly 3 million visitors to its dark skies, world class rock climbing, and wide valleys punctuated with the whimsical yuccas. The wild-armed tree has been closely linked with the Serrano, Chemehuevi, and Cahuilla people for centuries, the latter whose ancestors used the yucca’s leaves to weave baskets and make sandals. In recent decades, the park’s Joshua trees have been made famous in numerous fashion and film sets, like Selena’s 1994 “Amor Prohibido” music video and Bruce Springsteen's 2019 Western Stars. It’s a sought-after destination for travelers seeking spiritual connection and creative inspiration.
Many come to camp and rent home shares beside the trees, take photos next to them. Others get married among them. As a local of the area, Dr. Sweet explains that because of people’s affinity for the Joshua trees, the shaggy yucca has in many ways become a mascot for the effects of climate change in southern California, if not across the world. “Local events like ocean level rise or local imperiled species are often what makes the public act quickest in response to climate change,” Dr. Sweet says.
But Joshua trees are not only challenged by climate change within the national park. They face threats of warming temperatures and a variety of other dangers both in and out of the park’s boundaries. Besides the threat of development across the Mojave Desert, Joshua trees are further threatened by air pollution which fuels the spread of non-native grasses and increases the chance of wildfire.
This past May, outside the Joshua Tree National Park just south of the Twentynine Palms Highway, a 150-acre fire ignited on conservation land owned by Mojave Desert Land Trust when a man flicked a lit cigarette butt into dry brush while hiking. The fire burned close to the border of a plot that Dr. Sweet studied in her 2019 paper. The fire charred and killed acres of trees. Over 100 miles away as the roadrunner sprints, one of the densest woodlands in the world of eastern Joshua trees, Yucca brevifolia jaegeriana, were destroyed this past August during the catastrophic Dome Fire, a 43,273-acre fire in Mojave National Preserve that was estimated to have killed over a million Joshua trees.
Still, many desert conservationists are quick to say the tree is far from a lost cause. “It’s a species under threat but with serious efforts we believe the species can be preserved,” says Geary Hund, the executive director of the Mojave Desert Land Trust. To achieve this, MDLT is acquiring land in wildlife corridors—areas of natural habitat that connect flora and fauna otherwise separated by developed or cultivated land—to allow Joshua tree distribution to shift upwards in elevation or move northward in latitude in response to warming temperatures.
Currently, the western Joshua tree is now a candidate under consideration by the California Fish and Game Commission for protection under the California Endangered Species Act. In a formal petition filed by the Center for Biological Diversity in the fall of 2019, Dr. Sweet’s study was one of many that the group cited in their argument for the tree. If it’s granted this designation, the Joshua tree would be the first plant protected by law in California in response to climate change. Hund says that the tree’s protection would help conserve more forests from commercial, residential, and renewable energy development, setting up the species for more success in the future as climate change hastens.
Alongside the land acquisition and stewardship, MDLT also hosts a variety of plant conservation programs including a native plant restoration nursery and an extensive seed bank holding millions of seeds and spores of flora native to the Mojave Desert. The bank is one of a few actively collecting seeds of desert flora across California. Within the trust’s bank are over 50,000 Joshua tree seeds, small black discs that resemble miniature hockey pucks. And in the trust’s nursery behind their building, rows of western Joshua tree seedlings are held close together like eggs in a crate. Their flimsy lime green leaves rocket from the soil in every direction; these soft beginnings will eventually become the sharp bayonets of mature trees raised to the southern Californian sun. “As dire as some of this seems,” Hund says, “I’m optimistic that nature is very resilient, and that if human beings do their part to protect nature, it will do the rest.”
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