While some Joshua trees will hang on if humans rapidly lower their carbon emissions, if no action is taken to stop climate change we’ll lose nearly all of these iconic spiky trees, which only live in the area near southern California’s Joshua Tree National Park.
Published in the journal Ecosphere in June, the study combines on-the-ground observations with climate models to determine that a worst-case scenario where we continue with business-as-usual emissions would result in just 0.02 percent of the trees’ current range remaining in Joshua Tree National Park between 2070 and 2099. Even if we do all we can to mitigate climate change, only 18.6 percent of the trees’ original habitat would remain, the researchers found. Rising temperatures, worsening drought, and a loss of groundwater spell serious trouble for this tree.
This study adds to the previous literature by coupling models with observational data. The scientists and a group of more than a hundred volunteers collected data on and around living Joshua trees between 2016 and 2017, including information on the climate, topography, and local soil characteristics. The researchers also identified which trees were young to study how climate change is already impacting them.
They found out that young trees were already reacting to the changing desert conditions: They’ve been moving to higher, cooler climates in the national park, where more groundwater is available. Seedlings can’t store as much water as their older counterparts, an ability that allows Joshua trees to live up to 300 years, said Jules Bernstein, the senior public information officer for the University of California at Riverside, whose researchers helped conduct the study, to Earther. That means seedlings need more water in the ground, and such areas aren’t as common as they once were.
Part of what the study authors highlighted in the paper are other threats to the Joshua tree—like non-native species and wildfires. Wildfire activity in this part of the country is being enhanced by the smog that travels from the Los Angeles Basin. The smog leaves nitrogen on the ground, which acts as a fertilizer for non-native grasses that increase the region’s wildfire risk. That needs attention, too, if the tree is to be saved. The National Park Service has begun removing these invasive grasses as a result of this study, Bernstein told Earther.
But if we do manage to solve the problem of invasive species and wildfires, there’s still climate change.
Losing the Joshua tree wouldn’t just mean losing a beautiful sight; we’d lose a key part of the ecosystem. Animals like the yucca moth and desert night lizard rely on the Joshua tree for food and shelter. Without the trees, the entire ecosystem would transform, Bernstein said. Plus, more than 2 million people visited the park in 2015. All that tourism could be lost, too, dealing a major hit to the local economy.
Next, Bernstein said, the researchers want to learn how climate change is affecting adult Joshua trees. We know that it’s making it harder for seedlings to grow and that the warming climate will make the environment unsuitable in the future—but how are they feeling now? This information could help us understand what needs to be done here and now to save Joshua trees.
And there are a few things everyone can do to help. We can reduce our carbon footprints, for one. Bernstein also suggests more people could volunteer to help in these kinds of studies.
“This data has helped us take concrete actions to protect these trees,” Bernstein said. “I think that’s a really hopeful thing. It’s possible to do something.”
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