Recent research conducted by the University of California Riverside (UCR)at Joshua Tree National Park in the San Bernardino Mountains east of Los Angeles found that without a drastic reduction in carbon emissions the park would retain only 0.02 percent of Joshua tree habitat by 2070. The Joshua trees are located in California, Arizona, Utah and Nevada.
A desire to understand the problems facing this species in the face of climate change led UCR scientists to convene experts and dozens of volunteers to collect data on more than 4,000 trees. The researchers projected several future scenarios for the species, depending on the scale of efforts to combat climate change.
In the most optimist projection, where carbon emissions were reduced by a large proportion, showed that only 19 percent of the habitat the tree needs to live would be conserved. The most discouraging estimate noted that if nothing is done to reduce carbon in the atmosphere the iconic tree would disappear by the end of the century.
The fate of these particular and amazing trees is in the hands of the community. Their numbers will decline, but how much is up to us.
Lynn Sweet, Ecologist and project manager
On September 21st, 2021, a federal district court in Los Angeles has ruled that the U.S. Fish and Wildlife Service (the “Service”) violated the law when they failed to list the imperiled Joshua tree under the Endangered Species Act (“ESA”).
The Service disregarded overwhelming scientific evidence showing that climate change poses a major threat to the Joshua tree’s survival when the agency denied listing the species as threatened under the Act. The decision stems from a 2019 lawsuit filed by WildEarth Guardians, challenging the Service’s decision that the desert icon did not warrant federal protection, despite all the available scientific evidence pointing to the same conclusion: Joshua trees will be in danger of extinction throughout most of their current range by century’s end from climate change driven habitat loss, invasive grass fueled wildfire, and other stressors.
WildEarth Guardians first filed a petition to list the Joshua tree as “threatened” under the ESA in 2015 and the Service found the listing “not warranted” in August 2019. Under the Trump administration, the Service ignored every available peer-reviewed study to model future climate impacts to Joshua tree—all of which agree that the vast majority (roughly 90%) of the species’ current range will be rendered unsuitable by the end of the 21st century.
According to experts, one of the biggest problems Joshua trees face is the severe droughts in these areas, where the last one lasted 376 weeks. The study found that in the hottest and driest areas, adult trees do not produce as many young plants, and the plants that are born do not survive because they are not able to maintain water reserves to help them face extended periods of drought.
Although these trees in their mature age have the capacity to accumulate large quantities of water, the very long periods without the possibility of accessing the liquid have forced this species to migrate to higher elevations with a colder climate and more humidity in the soil.
By protecting the trees, they are protecting a lot of other native insects and animals that also depend on them.
Lynn Sweet, Ecologist and project manager
Severe droughts are not the only problem facing Joshua trees, as climate change is also affecting cassava moths, an insect they depend on to reproduce. A 2018 University of California Santa Cruz study found that yucca moths are not surviving in the higher elevations where Joshua trees are migrating.
The relationship of these two species goes beyond the pollination of the tree that the yucca moth helps with. These insects also need the plant as they lay their eggs inside the tree’s flower, which also serves as food for the larvae.
Another enemy of these two species is fire; less than 10 percent of Joshua trees survive wildfires, which have increased in California in recent years. According to the National Park Service, the tree was christened Joshua in the mid-19th century, when Mormon pioneers named it after the biblical figure Joshua upon seeing the tree’s branches outstretched in supplication, leading travelers westward, since when the tree’s image has become part of California’s popular culture.
