Cli­mate change tak­ing a toll on the iconic Joshua tree

Los Angeles Times - - CALIFORNIA - By Louis Sa­h­a­gun

JOSHUA TREE, Calif.— Un­der canopies of dead an­gu­lar branches and droop­ing fronds, UC River­side ecol­o­gist Cameron Bar­rows made his way across a for­est of skele­tal Joshua trees that have not re­pro­duced in decades.

As Bar­rows ex­plained, it’s a tough time to be a Joshua tree. Cli­mate change is tak­ing an enor­mous toll, and the cur­rent drought has has­tened the de­cline of a species that is re­garded as the sym­bol of Cal­i­for­nia deserts.

“For Joshua trees, hot­ter, drier con­di­tions are aprob­lem— but a big­ger prob­lem is that what lit­tle rain­fall oc­curs evap­o­rates faster,” Bar­rows said. “So, seedlings shrivel up and die be­fore they can put down strong roots.”

The re­gion, in­clud­ing nearby Joshua Tree Na­tional Park, has not reached av­er­age pre­cip­i­ta­tion rates of about 4 inches in sev­eral years. So­far this year, it’s got­ten 1.71 inches of rain.

If warmer, drier con­di­tions con­tinue in the com­ing decades, sci­en­tific model­ing sug­gests the trees will lose 90% of their cur­rent range in the 800,000-acre park by the end of the cen­tury.

With fund­ing from fed­eral wildlife of­fi­cials, Bar­rows is try­ing to find ways to as­sess the ef­fects of cli­mate change on Joshua trees and the many species they shel­ter: yucca moths, skip­per but­ter­flies, ter­mites, ants, desert night lizards, kan­ga­roo rats and 20 species of birds, in­clud­ing Scott’s ori­oles, lad­der--

backed wood­peck­ers and great horned owls.

There is more at stake than the fate of the park’s es­ti­mated 2.5 mil­lion Joshua trees, said bi­ol­o­gist Re­becca R. Her­nan­dez, a post-doc­toral fel­low at UC Berke­ley. “Be­yond its im­por­tance as a crit­i­cal refuge for desert species, the Joshua tree is a cul­tural sig­na­ture of Cal­i­for­nia’s desert land­scape,” Her­nan­dez said.

Joshua trees, which grow in the Mo­jave Desert and nowhere else, have be­come main­stays for movies, fash­ion shoots, ad­ver­tis­ing cam­paigns and wed­ding cer­e­monies. The one that adorned the cover of U2’s 1987 al­bum “The Joshua Tree” be­came a pil­grim­age site for fans from around the world un­til it was blown over by strong winds in 2000.

The species sci­en­tists know as Yucca bre­v­i­fo­lia isn’t ac­tu­ally a tree; it’s a suc­cu­lent. Joshua trees grow to 40 feet high, live more than 200 years and bloom spo­rad­i­cally. In 2013, ex­ten­sive stands were fes­tooned with yel­low and white bell­shaped blos­soms that drew tourists ea­ger to take in the scenery be­fore the bloom wilted in the desert sun.

They 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 imag­ined the trees as shaggy prophets, their out­stretched limbs point­ing the way to their promised land.

Dur­ing the 1980s, de­vel­op­ment in desert boom towns such as Lan­caster and Palm­dale re­placed about 200,000 Joshua trees with hous­ing tracts and shop­ping cen­ters. Many more were re­moved over the last decade to make way for re­new­able en­ergy fa­cil­i­ties.

In the 1990s, moist El Niño con­di­tions trig­gered ex­plo­sive growth of ex­otic grasses among the trees. Feed­ing off ni­tro­gen-laden smog waft­ing in from Los An­ge­les, the grasses have es­tab­lished them­selves, leav­ing Joshua tree forests vul­ner­a­ble to large-scale brush fires such as one that charred 14,000 acres in 1999.

Now, the big­gest threat is cli­mate change, which most of the trees may not be able to over­come. The globe’s av­er­age tem­per­a­ture is ex­pected to rise roughly by an ad­di­tional 5 de­grees to 7 de­grees Fahren­heit by the end of the cen­tury, sci­en­tists say.

Com­puter mod­els de­pict­ing the dis­tri­bu­tion of suit­able habi­tat af­ter a roughly 5-de­gree Fahren­heit rise show Joshua trees re­tain­ing just 2% to 10% of their cur­rent range, ac­cord­ing to stud­ies led by Bar­rows and pub­lished in the sci­en­tific jour­nal Bi­o­log­i­cal Con­ser­va­tion.

“Since they grow for about 200 years, we won’t see mas­sive die-offs in our life­time,” park Su­per­in­ten­dent David Smith said. “But we will see less re­cruit­ment of new trees.”

In a col­lab­o­ra­tive ef­fort launched this year, the park, the U.S. Fish and Wildlife Ser­vice and a re­search team led by Bar­rows or­ga­nized the first long-term project de­signed to mon­i­tor the Joshua trees’ re­sponses to cli­mate change and drought.

The data, col­lected with help from vol­un­teer cit­i­zen sci­en­tists from the non­profit group Earth­watch, will cre­ate base­line in­for­ma­tion to help guide con­ser­va­tion de­ci­sions as Joshua trees re­treat to cooler and wet­ter higher el­e­va­tions. The group has also es­tab­lished mon­i­tor­ing sta­tions to gauge changes in the dis­tri­bu­tions of Joshua trees and species they sup­port.

Will the re­gion have to change its name one day to, say, “Cre­osote Na­tional Park”?

“Nah,” Bar­rows said with a smile. “There’s still go­ing to be enough Joshua trees around here and there.”

Bar­rows scanned the drought-stricken Joshua tree wood­lands for signs of new life. Min­utes later, he spot­ted a knee-high bou­quet of dag­ger-like leaves.

“Look here, a baby,” he said, smil­ing down on the Joshua tree he es­ti­mated was about 10 to 15 years old. “Will it sur­vive? De­pends on how much rain we get.”

Pho­to­graphs by Allen J. Sch­aben Los An­ge­les Times

THE SET­TING SUN sil­hou­ettes a drought-stricken Joshua tree. The trees, which grow in the Mo­jave Desert and nowhere else, serve as a shel­ter for­many species and have be­come main­stays for­movies, fash­ion shoots, ad­ver­tis­ing cam­paigns and wed­ding cer­e­monies.

UC RIVER­SIDE ecol­o­gist Cameron Bar­rows in­spects a dry Joshua tree. He and oth­ers are study­ing the ef­fects of cli­mate change on the species.

Allen J. Sch­aben Los An­ge­les Times

CAMERON BAR­ROWS stands next to a parched tree. “For Joshua trees, hot­ter, drier con­di­tions are a prob­lem — but a big­ger prob­lem is that what lit­tle rain­fall oc­curs evap­o­rates faster,” he said. “So, seedlings shrivel up and die be­fore they can put down strong roots.”

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