The iconic western Joshua tree may become one of the first species listed as threatened primarily due to climate change under the California Endangered Species Act (CESA), potentially making it a landmark case in how species may qualify for legal protection in the future. If no action is taken to mitigate threats to the ancient species, recent climate models predict that the trees may vanish from the state by 2100.

Climate change is causing a domino effect of stressors such as fire, predation, and drought that are affecting the trees’ ability to successfully reproduce, adding to the threat posed by habitat loss. Advocates hope to prevent this extinction by listing the tree as threatened under state and federal endangered species protection laws, which would then legally require state and government agencies to make an effort to protect it from climate change. For now, the western Joshua tree (Yucca brevifolia brevifolia) is considered a candidate species, but a legal process is underway that will ultimately decide its fate.

“This is a species that’s prehistoric,” Jennifer Schwartz, a staff attorney at the nonprofit WildEarth Guardians said. “Joshua trees have been around for two-and-a-half million years and we’ve kind of managed to threaten it with extinction in the span of one-and-a-half human lifetimes.”

Aware of this threat, the Center for Biological Diversity (CBD) petitioned the state of California in October 2019 to list the western Joshua tree as threatened under CESA. California’s Fish and Wildlife Commission transferred the petition to the Department of Fish and Wildlife (CDFW), which then conducted a review of the petition and decided that listing the western Joshua tree may be warranted. The Commission then voted in September 2020 to move forward, making the tree a candidate for CESA.

Schwartz said plants can be easier than animals to list under the ESA because they are typically endemic to a small region, making it easier to identify a species’ critical habitat. However, Joshua trees cover a large range, making identifying their critical habitat more difficult.

According to Schwartz, “the models show [that] so much of that [area] is going to be lost. Even if we started taking immediate action on climate change, populations will be lost.”

Brendan Cummings, CBD’s conservation director who wrote the petition, said that even though the western Joshua tree has a large range, he believes legal protection is attainable.

“I believe that it can be saved and that protection under the California Endangered Species Act will help save the species,” Cummings said.

Protecting the Joshua tree through the legal system did not always seem practical. In 2019, the conservation group WildEarth Guardians had submitted another petition to the US Fish and Wildlife Service (FWS) to list both western and eastern species of Joshua tree as threatened under the ESA. After a year-long review process by the FWS, the tree was denied federal protection.

The FWS findings acknowledged that both species of Joshua tree face stressors, but ultimately concluded that it did not find the threats to be large enough in scale. It also noted that the trees still occupy their historical range.

WildEarth Guardians challenged the decision, and in September 2021, a United States District Court ruled that the FWS had violated the law when it failed to list both species of Joshua tree under the federal ESA. The court found the agency ignored the available science listed in the petition when making its decision, which it described as “arbitrary and capricious.” The FWS now must reconsider its previous decision.

Cummings decided to focus on the western species for the CBD petition because its range is primarily in California, with a small portion of it in Nevada. While the two Joshua tree species vary slightly in shape, size, and genetics, the main defining factor between the two is that they have different pollinating moths.

For Cummings, the recognition from the FWS in 2019 that the Joshua tree is two separate species changed the game. As a single species, the Joshua tree spanned four states and over 12 million acres of both public and private land, which made it a less-than-perfect candidate for protection under either federal or state law. The eastern Joshua tree is mostly found in Mojave National Preserve, which means it is protected under federal law, whereas 40 percent of the western species’ range is on private land, putting it at risk from development.

Models cited in Cummings’ petition also predict the western Joshua tree will mostly, if not totally, cease to exist in California by the end of the century, perhaps surviving only in the northeastern edges of its range. To be listed as a threatened or endangered species in California, the species only has to be imperiled in California, even if it exists in other states. This is another reason why Cummings wanted it listed under the state ESA.

“All those things came together, and it felt like the right time to make a go at protecting them,” Cummings said.

Todd Esque, a research ecologist at the US Geological Survey who studies the life cycle of Joshua trees, said the climatic threats to them mainly stem from the tedious and complex nature of its reproductive process.

Joshua trees are able to reproduce sexually, via pollinators, and asexually through their roots, which will produce genetically identical ‘resprouts.’ Resprouts can grow rapidly. According to Esque, a resprout can reach a reproduction life cycle within a couple of decades, whereas from a seed this takes about 70 years.

To successfully reproduce from a seed takes a combination of effort from moths and rodents, as well as pure luck. Esque explained that for a seed to grow, there has to be a year where the trees all are in bloom in order to be pollinated by yucca moths. This happens once every few years. The same year the trees are blooming, yucca moths also must have a healthy and active year. The effects of climate change on the moths are unclear.

If the Joshua tree is pollinated,, the tree drops its seed-filled fruit to the ground. Squirrels then collect the seeds and store them away across the desert. In order to begin growing, the seed must be stored at about two centimeters underground.

If the seed is lucky, the squirrel will store the seed at the right depth and forget about it.

“The more we study them, the more we find it’s incredible that they can ever make it, and yet, they’re out there … so far,” Esque said.

Then, the weather has to provide enough rain within 18 months of the seed being planted, or else it may rot. Rainfall is scarce in the desert under normal conditions, with one wet year often followed by several dry years. Thanks to climate change, these cyclical droughts are intensifying in length.

Increasing incidence of wildfire poses an added threat.

“Just like when a human is burned, if a large part of our bodies are burned, it’s almost nearly always fatal,” Esque said.

When a Joshua tree is burned, it loses all the water in its tissue and essentially dehydrates. This puts the tree at a greater risk for infection. However, Esque’s research found that there is some hope for Joshua trees after a fire because of their vast, sprawling underground root systems. As long as there is enough rainfall after a fire, the tree’s roots can still generate resprouts.

But after a fire, Joshua trees also face greater risk of predation. With fewer food options, predators like rabbits, insects, and rodents devour Joshua tree resprouts.

Cummings said he believes that if the western Joshua tree is listed as threatened under CESA, it could be one of the most impactful listings in its history not just because it would be the first due to climate change, but because it would change how CESA is enforced and land is used, especially in the desert. He added that the tree is impossible for developers to ignore, hide, or remove illegally due to its large size, making it easier to monitor the species.

“You can’t hide a Joshua tree,” Cummings said. “We can literally see them from space. … we know if you illegally removed one without a permit.”

Due to the trees’ candidacy status, they are temporarily protected while the CDFW prepares a review of the case. While a ruling on a permanent listing was originally expected in October 2021, the California Fish and Wildlife Commission has been waiting on the review by the CDFW, which was granted a six-month extension. The CDFW submitted the status report last week, recommending against listing.

“California wildlife officials just proposed open season on Joshua trees,” Cummings said in a press release. “Before state protections took effect, developers were bulldozing these beautiful, fragile trees by the thousands to build roads, warehouses, power plants, strip malls and vacation rentals. If Joshua trees are to have any hope of surviving in a warming world, we have to stop the widespread killing of them.”

The Fish and Wildlife Commission will vote on whether the western Joshua tree will be listed as threatened under state law in June. The commission’s final vote will determine if the tree is officially added to the CESA. As a listed species, it would be illegal for any part or product of the western Joshua to be, “taken” (i.e., killed), possessed, purchased, or sold without a state approved permit, according to the California F.W.S.

Cummings believes the commission will vote to list the tree as threatened because the members are supposed to vote solely based on the science.

“If they vote no,” Cummings said, “we’re pretty confident a court would overturn it.”