• Katherine Lofts

Joshua Tree and Climate Change

Photo by: Konstantia Koutouki

Adam Clayton, the bass guitarist of the famous rock band U2, described the group’s desert influence in the following way, “The desert was immensely inspirational to us as a mental image […] Most people would take the desert on face value and think it’s some kind of barren place, which of course is true. But in the right frame of mind, it’s also a very positive image, because you can actually do something with blank canvas, which is effectively what the desert is.”

In 1987, U2 released their landmark ‘Joshua Tree’ album. Its art for the record depicted photos of the American desert landscapes, and the musical phenomenon led to a wave of global attention to the Joshua trees.

At the end of January 2019, following the longest-ever government shutdown in United States history, news outlets began reporting on damage to Joshua Tree national park. A lack of staff supervision during the shutdown had led to a “state of chaos” in the park, as visitors engaged in vandalism, disturbed fragile desert soil, and cut down some of the park’s namesake Joshua trees. According to the park’s former superintendent, it could take hundreds of years for Joshua Tree to recover.

Unfortunately, unruly park visitors are not the only threat to the Joshua trees (Yucca brevifolia) that call the park home; they are also under increasing stress due to climate change. The plants grow in the cooler, higher elevation climate of the Mojave Desert, but hotter temperatures, increasing drought, and the loss of groundwater are taking their toll. A recent study found that unmitigated climate change with business-as-usual emissions would result in a mere 0.02 percent of the trees’ current range remaining in Joshua Tree National Park between 2070 and 2099. But even if significant action is taken to mitigate greenhouse gas emissions, “only 18.6 percent of the trees’ original habitat would remain”, effectively decimating the population.

This projected decline is perhaps all the more alarming given the changes the plant has successfully weathered over the millennia. Joshua trees have existed for 2.5 million years, and over that period have experienced many climatic changes. Indeed, 25,000 years ago, the Mojave landscape was a very different place. Although much of North America was covered by ice in this period, the climate of the Mojave was rainy, blanketed by forests, freshwater lakes, and rivers. It was also home to a wide range of animals, from bears, wolves, and elk, to mammoths, ground sloths, and saber-toothed cats.[i] During this period, Joshua trees had a far wider range than they do today – likely stretching from Death Valley in California all the way south to the Colorado River delta in Mexico. [ii] But twelve thousand years ago, as North America’s glaciers began to recede and the polar jet stream moved north, a warmer, dryer climate took hold in the Southwest. Rivers and lakes dried up and the forests largely disappeared. Joshua trees survived this transformation, moving slowly to cooler, higher elevations, and now grow primarily on slopes at elevations above 3,000 feet. [iii] But while past climatic changes took place over millennia, allowing Joshua trees time to adapt, the current pace of global heating is proving too much. While trees at higher elevations will likely be able to survive for longer, even those areas will eventually become too inhospitable.

Of course, here are other immediate threats to Joshua trees. As invasive grasses have proliferated, we are witnessing an increasing amount of devastating fires ravaging the lands. “These plants didn’t evolve with fire, so they just don’t come back from it,” explained David Smith, Joshua Tree national park’s superintendent.

What is at stake with the loss of the Joshua tree? Famously described as “the most repulsive tree in the vegetable kingdom”, these striking trees have captivated the imaginations of those who have encountered them. Prior to the arrival of Europeans in 1769, the area now known as Joshua Tree National Park was inhabited and used by the Serrano, Cahuilla, Mojave, and Chemehuevi Indigenous nations. [iv] These nations used the Joshua tree for several purposes: “tough leaves were worked into baskets and sandals, and flower buds and raw or roasted seeds made a healthy addition to the diet.” [v] The local Cahuilla have long referred to the tree as “hunuvat chiy’a” or “humwichawa.” [vi] Natives also used the dye from the tree’s reddish rootlets for decorating the baskets they made.

In addition to their cultural significance, Joshua trees play an important role in the ecosystem, providing food and shelter for a number of mammals, birds, reptiles and insects. While red-shafted flickers drill holes in the branches to make nests, which can be later occupied by other birds, desert night-lizards live in the dead leaves and branches, and woodrats gnaw off the spiny leaves for their nests. [vii] The largest trees of the yucca family also have an interesting co-evolutionary relationship with the yucca moth, upon which the trees rely exclusively for pollination. The moths lay their eggs inside the ovary of the Joshua tree flower. In the process, they collect pollen with a pair of long, coiled ‘tentacles’ and deposit it in other flowers, resulting in pollination. In turn, the moth’s eggs hatch into larvae that feed on some of the tree’s seeds. [vi] [vii]

Losing such an important tree would be devastating for the environment, and for the people who identify with these trees as part of their home.

About the Author

Katherine is a lawyer whose work focuses on climate change, human rights, and environmental governance. Originally from Vancouver Island, she has lived in Europe and Asia, and currently resides in Montreal.

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