Will climate change kill off Joshua trees? - Hi-Desert Star: News

Will climate change kill off Joshua trees?

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Posted: Wednesday, November 9, 2011 12:50 am | Updated: 12:49 pm, Thu Mar 15, 2012.

JOSHUA TREE NATIONAL PARK- It's hard to imagine the national park's iconic Joshua trees disappearing, but a few ecologists say climate change could threaten the species.

Dr. Cameron Barrows, an assistant research ecologist at University of California at Riverside's Palm Desert campus, has spent the last few years working with Joshua Tree National Park to study environmental changes and their effects on plants and animals. Barrows conducts many of the research initiatives at the university's Center for Conservation Biology.

Barrows creates scientific models and uses what he calls "citizen scientists" to collect information in the field about Joshua tree distribution in JTNP.

"The models we create show how Joshua trees or other species change in response to a warming climate," Barrows said from his office in Palm Desert Monday.

Based on his findings, Joshua trees will survive in the national park, but not at the levels we see them at today.

"My results show the park should provide an important refuge for these iconic plants. Their area of suitable habitat will likely decline, perhaps leaving them to only 10 percent of their current distribution, but they should survive," Barrows said.

Together with his citizen scientists, Barrows used a model that looks at Joshua tree seedlings and the current 1 degree annual warming change, which showed the young trees' populations declining in response to a warming climate.

Using a map that portrays U.S. "hot spots," which are areas that will be most impacted by climate change, Southern California, and the Mojave Desert in particular, looks to be bearing the brunt of the gradual heat wave.

Barrows explains that the Joshua trees in the Morongo Basin are currently on the fringe of their population area, making them more vulnerable than the Joshua trees in other parts of the Mojave Desert.

He's careful to point out the difference between weather and climate, saying there's a lot of variability in climate changes across the nation. Not all species of plants and animals will be affected the same way, and species in different regions will have varying degrees of resiliency to the changes.

"It's not changing equally, everywhere," Barrows said.

The study of Joshua tree populations isn't a new concept, but considering the impacts of climate change on their survival is.

National park spokesman Joe Zarki said other studies have been done on the centuries-old trees, but Barrows and ecologists from the U.S. Geological Survey are some of the first to link climate change to population decreases.

A study conducted by Kenneth Cole, Lara Schmit and Catherine Puckett used future climate modeling to conclude that Joshua trees would likely be restricted to the northern part of the species' current range, wiping them out of the national park.

The study suggests large animals like prehistoric ground sloths were able to disburse Joshua tree seeds over larger territories.

Future Joshua tree migration, the researchers concluded, will be slowed and steady temperature increases "will likely eliminate Joshua trees from 90 percent of their current range in 60 to 90 years," according to a USGS release on the study.

"There does seem to be a trend showing lower number of Joshua trees per unit of land study," Zarki said of previous studies looking at population densities, without looking at climate change.

He acknowledged both Barrows and the USGS's research and models, but said the park still lacks "definitive" data on how the trees will fare over the next century.

Zarki said the park is slated to hold a meeting next month on the health and future of the park's namesake trees.

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