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Joshua Trees Decline Due to California Drought

Jun 08, 2015 12:18 PM EDT
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Joshua trees, a beloved and iconic desert species in California, is currently in decline due to drought and climate change.

According to University of California (UC), Riverside ecologist Cameron Barrows, tree seedlings are shrinking and dying before they are able to spread their roots.

"For Joshua trees, hotter, drier conditions are a problem - but a bigger problem is that what little rainfall occurs evaporates faster," Barrows told the Los Angeles Times. "So, seedlings shrivel up and die before they can put down strong roots."

California is in the middle of the worst drought in a millennium, which is rapidly depleting its water supply. One NASA scientist even recently warned that the state has merely one year of water left.

The region, which includes Joshua Tree National Park, has not reached average precipitation rates of about 4 inches in several years. So far this year, it's gotten 1.71 inches of rain. If these warmer, drier conditions continue in the coming decades, then the trees will lose 90 percent of their current range in the 800,000-acre park by the end of the century, climate models suggest.

This isn't just bad news for the Joshua trees themselves, but also for the many critters that take shelter under them. This includes yucca moths, skipper butterflies, termites, ants, desert night lizards, kangaroo rats and 20 species of birds.

"Beyond its importance as a critical refuge for desert species, the Joshua tree is a cultural signature of California's desert landscape," added UC Berkeley biologist Rebecca R. Hernandez.

Interestingly, the Joshua tree (Yucca brevifolia) isn't actually a tree at all, but a succulent. They can grow up to 40 feet high, live more than 200 years, and bloom sporadically with yellow and white bell-shaped blossoms. (Scroll ro read on...)

These succulents, which grow in the Mojave Desert exclusively, were named for the biblical figure Joshua by members of a band of Mormons traveling through the Cajon Pass back to Utah in 1857. They believed the tree was a "shaggy prophet" of sorts, their limbs pointing the way towards the promised land.

Since that time, Joshua tress have withstood all sorts of threats and made it out on the other side. For example, in the 1980s, about 200,000 Joshua trees were removed to make way for new developments such as housing tracts and shopping centers. Then, in the 1990s, moist El Niño conditions triggered the explosive growth of exotic grasses, leaving Joshua trees vulnerable to large-scale brush fires. One such blaze even charred 14,000 acres in 1999.

But now, the new threat is climate change and drought. And despite their resilience in the past, scientists worry that the estimated 2.5 million Joshua trees left are in danger this time.

Computer models by Barrows and his team show the species retaining just two to 10 percent of its current range if global temperatures rise by 5 degrees Fahrenheit.

"Since they grow for about 200 years, we won't see massive die-offs in our lifetime," park Superintendent David Smith told the LA Times. "But we will see less recruitment of new trees."

Moving forward, Barrows plans to monitor Joshua trees' responses to climate change and drought, which will provide baseline information to help guide conservation decisions in the future.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

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