- Western Joshua trees in California are increasingly threatened by changing climate conditions, including rising heat, increasing drought, more frequent wildfires, and by expanding renewable energy and housing developments.
- Despite increasingly harsh conditions, adult Joshua trees are expected to remain common through the end of the century, but young trees will not survive across most of their current range, scientists warn.
- Although the U.S. Fish and Wildlife Service has declined to protect eastern and western Joshua trees under the Endangered Species Act, California passed a state law to protect its western Joshua trees in 2023.
- Scientists warn that these trees need climate action to survive the century.
In early springtime in the Mojave Desert, Joshua trees provide one of the few foods available to many of the wildlife species in this part of the southwestern U.S. Stretching above the surrounding dry vegetation and desert soil, the tall yuccas blossom with clusters of large white flowers that beckon insects, birds, deer, cattle, ground squirrels and pack rats.
“All of them are coming and feeding there because it’s a resource that exists in a pretty bleak environment,” said Chris Smith, a plant ecologist at Willamette University who studies Joshua tree survival and genetics. The trees also provide nesting locations for birds and habitat for the California night lizard (Xantusia vigilis).
But these days, it’s the Joshua trees that need refuge. As human-caused climate change makes the deserts of the United States increasingly inhospitable and development projects threaten habitat, even desert-adapted plants such as the Joshua tree face an uncertain future. Although adult trees appear stable for now, young trees are struggling to survive. California is trying to protect one of its Joshua tree species through legislation, but without climate action, scientists and policy experts alike warn that the state may not be able to save the beleaguered plants.
Joshua trees are desert succulents with crowns of spiky green leaves that grow in the Mojave, Great Basin and Sonoran deserts of the western U.S. Joshua trees can reach more than 12 meters (40 feet) tall and can live for several hundred years. There are two species: the western Joshua tree (Yucca brevifolia), which lives mostly in California’s Mojave Desert, and the eastern Joshua tree (Yucca jaegeriana), which is scattered across California, Nevada, Utah and Arizona.
If greenhouse gas emissions continue apace, scientists predict that Joshua trees may lose up to 80% of their current habitat by century’s end. In California’s Joshua Tree National Park, only 0.02% of habitat for its namesake plant will be livable by 2100, according to research led by Lynn Sweet, a plant ecologist at the University of California, Riverside’s Center for Conservation Biology.
Habitat loss is already occurring across California. “What will make a difference is if there is action on climate change,” Sweet said.
‘A forest with no young’
Although adult Joshua trees are tolerating increasingly harsh conditions, young Joshua trees are struggling to survive. They’re more sensitive to heat, drought and predation, and don’t reach sexual maturity until 50 to 70 years of age.
On the landscape, there’s something of an optical illusion: Joshua trees are plentiful in some rugged desert locations, and may continue to be into the middle of the century, as the U.S. Fish and Wildlife Service (USFWS) noted when it declined to federally protect them under the Endangered Species Act. But these are what Brendan Cummings, conservation director at the Center for Biological Diversity, calls “zombie forests.”
Cummings explained that “even under worst-case climate scenarios, we’ll probably still have some adult Joshua trees mid-century, but we’ll have virtually no recruitment. A Joshua tree forest with no young is a zombie forest — it’s living dead. They’re live individuals, but there’s zero future for [the forest].”
Complicating matters is the fact that no one knows whether the specialized yucca moths that pollinate Joshua trees are going to survive in a changing climate. Tegeticula synthetica pollinates western Joshua trees, while T. antithetica pollinates eastern Joshua trees. The moths fertilize the plants by moving pollen between them, then lay eggs in their flowers. Their larvae chomp through some of the trees’ seeds, leaving others to grow into new plants.
Despite the threats Joshua trees face, the USFWS has repeatedly declined to protect them, saying their populations look stable through the middle of the century. The nonprofit WildEarth Guardians sued the agency after its determination in 2023.
In May 2025, U.S. District Judge Wesley L. Hsu ruled against USFWS, writing that it’s “essential that the Service considers climate change’s effect on habitat suitability in relation to young Joshua trees, and not just the persistence of stronger, adult Joshua trees.”
It’s unclear how USFWS will respond. According to Patrick Parenteau, an emeritus professor of environmental law at Vermont Law School and an Endangered Species Act expert, the agency could simply “check all the boxes” by quickly redoing its analysis and still conclude that Joshua trees are not at risk of extinction. Or the agency may appeal the ruling. USFWS didn’t respond to Mongabay’s requests for comment on the ruling.
Meanwhile, in California, officials are working to protect the western Joshua tree within its borders. Their plans have been contentious: Cummings said that about 40% of the stat’s western Joshua tree range is on private land. The pressure for more housing construction, combined with California’s renewable energy goals, has pitted developers against conservationists, according to CalMatters.
In 2023, California enacted the Western Joshua Tree Conservation Act, which established rules for moving or trimming trees, and created the state’s Western Joshua Tree Conservation Fund.
According to Cummings, the federal ruling lends more credibility to California’s reasons for protecting its Joshua trees. He also said California’s law will be a “kick in the pants to federal agencies that the Joshua tree protection issue is not going away, and they need to vastly improve management of Joshua trees on the federal level.”
Migration is not the solution
Joshua trees won’t adapt to changing climatic conditions on their own, because they evolved under vastly different ecological conditions and can’t keep up with today’s rapid changes.
Joshua trees produce masts of seeds that once traveled across the landscape in the bellies of now-extinct giant sloths, which roamed North America until about 12,900 years ago. Today, these trees rely on antelope squirrels and other rodents to disperse their seeds, and rarely grow more than about 10 m (30 ft) from their parent plants.
Joshua trees may sometimes reproduce clonally, growing new individual plants from underground rootstocks called rhizomes. But either way, natural migration of Joshua trees to more climate-friendly regions is unlikely.
Smith, the ecologist at Willamette, said he doubts that people can save Joshua trees through assisted migrations. Moving the gangly, spiky trees would be “logistically incredibly challenging,” he said, and scientists would also have to figure out how to move their pollinators. Otherwise, relocated Joshua trees would be more like a botanical garden or a zoo, not an ecosystem, which Smith said is “not a good conservation strategy.”
Rather than trying to move trees, Smith said, California should focus on finding and protecting climate “refugia,” pockets of habitat that likely will persist even in the face of climate change, generally located at the upper elevations of current Joshua tree ranges.
But these refugia face their own dangers: development and wildfires that are fed by invasive grasses. A recent study found that wildfires are the single biggest threat to Joshua tree climate refugia, which face more than a 40% chance of igniting. Joshua trees often don’t survive blazes and struggle to regenerate or recolonize afterward. The second-biggest threat is wind and solar farms.
“The big question about whether or not Joshua trees can exist in the future is: ‘Are there places where the climate will be hospitable enough that they continue to grow?’” Smith said. “And where are those places, and can we make sure that they don’t burn up in wildfire, or we don’t build a Walmart on them, or they don’t get turned into solar fields?”
In Joshua Tree National Park, managers are trying to control invasive grass, hoping to protect refugia from future fires. But ultimately, Smith said, long-term Joshua tree conservation is bigger than California — it requires global climate action. Otherwise, he said, “I think we may kind of be fiddling while Rome burns.”
Banner image: Sunset at Joshua Tree National Park. Image courtesy of National Park Service/ Emily Hassell.
Citations:
Borchert, M. (2016). Rodent removal of fallen Joshua tree (Yucca brevifolia) fruits. Bulletin of the Southern California Academy of Sciences, 115(3), 146-155. doi:10.3160/0038-3872-115.3.146
Esque, T. C., Medica, P. A., Shryock, D. F., DeFalco, L. A., Webb, R. H., & Hunter, R. B. (2015). Direct and indirect effects of environmental variability on growth and survivorship of pre-reproductive Joshua trees, Yucca brevifolia Engelm. (Agavaceae). American Journal of Botany, 102(1), 85-91. doi:10.3732/ajb.1400257
Shryock, D. F., Esque, T. C., Berry, G. A., & DeFalco, L. A. (2025). Assessing uncertainty in forecasts of refugia for Joshua trees using high-density distribution data. Ecosphere, 16(6), e70308. doi:10.1002/ecs2.70308
Sweet, L. C., Green, T., Heintz, J. G., Frakes, N., Graver, N., Rangitsch, J. S., … Barrows, C. W. (2019). Congruence between future distribution models and empirical data for an iconic species at Joshua Tree National Park. Ecosphere, 10(6), e02763. doi:10.1002/ecs2.2763
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