Peculiar and bristly, Joshua trees rise from the arid plains of the Mojave Desert. There is water in North America’s driest desert but it’s scarce, and plants like this one make every drop count.
Surviving on about 2 to 8 inches of rainfall per year, the Joshua tree has been existing in baked valleys in the southwest for centuries. However, the tree might not make it to the end of the next one.
Certainly not without its impressive flora, the Mojave Desert conjures up images of forked Saguaro cacti silhouetted against the blood red sun. But, amid the almost alien scrubland, where plants grow in quirky shapes and sizes, the Joshua tree stands tall as a particularly striking yet underrated symbol of strength and survival.
The Joshua tree’s roots run shallow and deep. Figuratively, they have a grip on culture. Iconic in many ways, the plant’s outstretched branches mimic a call to the heavens. The tree apparently inspired Mormon settlers on a bible-esque journey across lands in the shadow of the Sierra Nevada mountains.
With its name above the door of California’s Joshua Tree National Park, the species’ image has inspired works of art. Perhaps its most famous artistic incarnation came in Anton Corbijn’s photos for a little known 1987 record by U2. According to conservationists, the sleeve of The Joshua Tree album could be where we end up turning to if grim analysis predicting the tree’s demise comes to pass.
Western Joshua tree
Geography has yielded two different species of the Joshua tree. Western Yucca brevifolia are located primarily around southern California, Nevada, Arizona and Utah, while the smaller Yucca jaegeriana can be found in the eastern band of the Mojave Desert.
Growing up to nine meters before branching, the western Joshua tree can take nearly 60 years to mature into a not inconceivable 10-15 metre stature. Amazingly resilient and somewhat mystifying, the trees can bear both alkaline and saline desert soil. The plants can live for more than 150 years. But aging the trees can be a tricky task. Technically a succulent, the trees do not have annual growth rings.
With thin fibrous able to suck up moisture from about 10 meters underground, and rigid, waxy leaves funnelling rainwater towards its base, the plant is primed for an existence marked by scarcity.
While rainfall is infrequent, the tree can rely on a unique relationship with another desert inhabitant - the Yucca moth. In return for providing the Yucca’s larvae with fruit, the moth pollinates and spreads the seed of the desert plant.
Despite their hardiness, the Joshua tree may not pull through the current climate predicament. It has implications not just for the tree but other desert creatures too, according to Brendan Cummings, conservation director with the Center for Biological Diversity.
‘With its specialized, mutualistic relationship, if we lose the Joshua tree we lose the Yucca moth. A whole suite of animals live amongst the tree and eat its seeds. It’s a big part of the fabric of the Mojave Desert ecosystem,’ Cummings explains.
Temperature increases and urban sprawl are endangering the Joshua tree. Conditions for growth are becoming less friendly, meaning the trees are finding it difficult to multiply and develop their robustness. They are also coming under increasing attack by invasive grasses and bushfires.
In a study published in the peer-reviewed journal Ecosphere this year, researchers predicted the population of trees in Joshua Tree National Park to be all but eliminated by the end of the century. If current climate trends and damaging human behaviour persists, it is thought that the tree will maintain just 0.02% of its range.
Glimmer of hope
Cummings lives in the Mojave Desert. He’s watched the tree’s slow decline in recent years. He’s witnessed trees ‘uprooted’ and ‘bulldozed’ to make way for roads and shopping malls. He’s seen how nitrogen deposits from Los Angeles smog has nourished invasive grassland, increasing the risk of bushfires.
Cummings says persuading the California government to protect the Joshua tree under the state’s Endangered Species Act is the way forward.
‘What scientists have learned over the past two decades, with much more dire knowledge over the past six months or so, is that the Joshua tree’s current existence is actually pretty tenuous,’ Cummings explains in a call from his home near Joshua Tree National Park.
‘It is a relatively abundant, decent size range species, so intuitively people don’t think of it as endangered.’ However, there are indications that the tree is failing to reproduce at a time when it really can’t afford to.
By petitioning the California Fish and Game Commission, it appears that Cummings and his fellow wildlife activists won’t let the tree go down without a fight.
‘Increasingly, we are finding more dead Joshua trees. The major concern is the failure of reproduction in the lower, hotter drier parts of the range,’ Cummings adds.
‘Even under our most optimistic climate scenarios - say if society finally gets together and goes carbon neutral by mid-century - it is still going to be a lot hotter than it is today. Under those scenarios, the tree loses three-quarters or more of its range.
‘Under business as usual scenarios, if we don’t get it together, the Joshua tree is gone.’
Pinning his hopes on local California authorities rather a Trump government which has arguably taken the teeth out of environmental legislation, Cummings believes the Joshua tree has a chance of survival if action is taken soon.
‘We used to have one of the best night skies where you could see the stars. Now you can see the glow of Yucca Valley [a town in San Bernardino County]. There are many developments that have just consumed the natural desert habitat,’ he says.
By getting the tree listed as an endangered species, Cummings says agencies would be compelled to take action, and the brakes could put on habitat destruction.
‘For example, about 40% of the Joshua tree’s range is on private land. If a developer wants to build a shopping mall he can bulldoze the trees. If it is protected, they won’t be able to do that without a more complicated permitting regime.
The sands might be currently moving in the wrong direction for the desert tree’s existence. But, there is a glimmer of hope, Cummings says. It’s not too late to change our behaviour.
‘We have some time to save the species if we do it right. If we treat the species correctly, the Joshua tree can become a symbol, not just of the climate change threat, but also of a successful response to climate change.’