The days of the most iconic tree in the American Southwest may be numbered.
The Joshua tree has always been a strange one. It is covered in layers of shaggy bark. Its spiny leaves might remind you of a cactus or a pine tree, but it is much more closely related to asparagus. While we mostly just enjoy looking at them today, in the past, people found all sorts of uses for the odd plant. Native Americans wove baskets and sandals from their tough leaves and supplemented their diet with their flowers and seeds. Later on, early Mormon immigrants would use their trunks and branches to make cattle fencing, or burn them to power their steam engines.
The economic and cultural uses of Joshua trees never became widespread in part because the trees themselves have a very limited range. They are found almost exclusively in the Mojave Desert between 1,300 – 5,900 feet in elevation. They can only thrive under certain conditions, and those conditions are being threatened by climate change. Nowhere can this be seen more clearly than in Joshua Tree National Park, a 1234 square mile patch of protected desert in California where their namesake is being threatened.
Dr. Cameron Barrows, an ecologist from the University of California, has been studying the impact of climate change on desert life in the area. When surveying Joshua tree populations, he found something that disturbed him. While he could find adult Joshua trees, some as old as 250 years old, young trees were often missing entirely.
“We want to see babies,” said Dr. Barrows. “And what we’re not seeing are individual seedlings that are coming up.”
At many of his sites the youngest trees were 30 – 40 years old. Seedlings are dying, and he thinks that climate change is the culprit. While the trees are well suited for the historic temperatures in the area, even small changes could make them unable to survive. They could lose as much as 90% of their habitat to climate change over the next century – But hope remains in that final 10%.
At higher elevations, young Joshua trees can find their footing in the cooler and wetter environment. “There are these little niches within this landscape that should be able to sustain Joshua trees,” Barrow says of his findings. In these places, young Joshua trees are abundant, and it’s a good thing they are. In a hundred years, we may not be able to find them anywhere else.
Climate change poses a unique challenge for the National Park Service. One of the traditional goals of conservation has been to preserve habitat where threatened species live. Now, they have to look ahead and consider where species might find hospitable in the climate of tomorrow. If wildfires or invasive species ravage the final strongholds of Joshua trees, it could mean the end for the weird plants we’ve admired for so long.
It’s going to be a tough century for conservationists, but research helps make sure that we’re going in the right direction. There’s still time left to help the Joshua trees and other species affected by climate change, but that time won’t last forever.
- Kate Dzikiewicz, Paul Griswold Howes Fellow