Will California’s Drought End the Joshua Tree?

New research shows that the bulk of the national park’s iconic plant are in jeopardy from exceptionally dry conditions

Joshua trees have a fragile root system that has suffered from California's excess heat and dryness. (Christopher Michel/Flickr)
Photo: Christopher Michel/Flickr Christopher Michel

Jason Bruecks has taken hundreds of hikes in his life, but one in particular stands out: his first full moon hike through Joshua Tree National Park.

“I can still see it now—the silhouettes of Joshua trees against the large, monzogranite rocks. It was quite extraordinary,” says Bruecks, owner of Distance 2B Traveled, a hiking and outdoor adventures company. “It recalled ancient people standing in an eerie and beautiful landscape.”

Those shaggy, spiny trees, which only exist in the Mojave Desert, are a key reason why Joshua Tree National Park was created in the first place. But climate change and California’s historic drought have combined to fundamentally transform the park’s delicate ecosystem—and, with it, the park’s identity.

If dry, hot conditions continue, Joshua trees could lose 90 percent of their range within the park by the end of the century, says Dr. Cameron Barrows, a research ecologist with University of California Riverside's Center for Conservation Biology. That means that existing trees would remain, since they can grow to be hundreds of years old, but they wouldn't produce new trees in 90 percent of their current area. "For a relatively large plant, Joshua trees have a fairly fragile root system," Barrows says. "The big, established trees can survive multiple years of drought or heat, but it's the little guys—the seedlings—who can't handle this kind of temperature or amount of rainfall. This is the future we're looking at." Think of it as a country where the current population continues, but there are few young to replace those who grow old and die.

Barrows recently completed the first year of a 20-year climate change research project in Joshua Tree National Park—the largest such study in the park’s history. He wants to assess the effects on Joshua trees and the 40 mammal species, 700 plant species, 240 types of birds, and 40 different reptiles that call the park home. The idea is that tracking these species now will ultimately help shape strategies to stem the decline of the park's biodiversity in the future.

“The Joshua trees represent the canary in the coal mine,” says David Smith, superintendent of the park. “This is a great example of how we can be looking for an indicator species to demonstrate what happens when temperatures rise and weather patterns change. All park rangers should be looking at these things.”

About 1.5 million people visit Joshua Tree every year. Last year alone, visitors to Joshua Tree spent over $73 million in communities near the park, supported 1,030 jobs in the area and had a cumulative benefit to the local economy of $97 million, according to a report from the National Park Service.

Most visitors come to play on the park’s 8,000 rock climbing routes and 191 miles of hiking trails. It's the trees, though, that are the centerpiece of this desertscape—but they're not technically trees. The Joshua tree is actually a type of yucca that exists only in this part of the world. In the 1800s, a group of Mormon pioneers crossing the desert thought the plant's skyward-reaching limbs resembled the prophet Joshua, throwing his hands up in prayer. They've been known as Joshua trees ever since.

At almost 800,000 acres—slightly larger than Rhode Island—the park is an amalgam of the dry, warm Colorado Desert and the cooler, wetter Mojave desert, straddling the terrain where the two meet. When rain falls, Joshua trees absorb it into their cork-like trunks and conserve that water for years. But it has been several years since the park experienced its historic average of annual precipitation of four inches per year. As desert residents, the trees are reasonably adapted to dry conditions, but they will struggle through the decade-long megadroughts that are predicted to parch the state in the near future. “Joshua trees are going to find those niches where they can survive in the high elevations, but it’s going to be difficult,” Smith says. “The rate of [climate] change is extremely rapid, and Joshua trees can’t run for the Sierras [mountains] on their own.”

Hence the imperative nature of Barrows’s research. He and fellow researcher Josh Hoines, resources division chief for Death Valley National Park, began planning the climate change study three years ago. It involves dividing the park into 27 square plots within three different vegetation zones. With a team of citizen scientists, the researchers recorded data on reptiles, birds, and animals, and monitored the desert vegetation, tagging and measuring the plants within each plot. That includes Joshua trees as well as all the species that rely on them—the wrens and owls who build nests among the prickly branches, the lizards who feed on insects under the bark, the woodrats who gather Joshua tree leaves for their nests, and the yucca moths who pollenate the trees. 

“One of the most important aspects of our research is that we aren’t just relying on models and arm-waving to predict a climate future,” Barrows says. “We are out there measuring how lizards and junipers and creosote bushes and Joshua trees are responding to climate change as it changes.” The researchers have already discovered that some lizards have abandoned lower elevations altogether, while some birds have also been moving toward higher elevations. "The preliminary results are actually reasonably optimistic," Hoines says. "The species are still there. We're just beginning to understand how to help them."

Research is only the first step in protecting the trees. A management plan is sure to follow, but it’s unclear exactly what it would look like. Park officials have begun adapting to the dry conditions by employing a wildland fire crew tasked with addressing every lightning strike or human-caused fire, Smith says. It's a responsive approach, and if the park's ecology is to survive, staffers need to get proactive. But just how they'll do that is unclear.

“There are no easy answers,” Hoines says. “If you start to pull on the string in one part of the ecosystem, it will unravel another part of the ecosystem.” In the future, he says, parks might try to manage plant loss by collecting seeds and genetic material for restoration. “But the best thing we can do is preserve the ecosystem in the first place."

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