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October 15, 2019

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Mount Charleston home to species nowhere else on earth

Acastus Checkerspot butterfly

U.S. Forest Service / Courtesy

Spring Mountains Acastus Checkerspot butterfly

Las Vegas’ nearest island is hundreds of miles away. But a “sky island” can be found right in the city’s backyard.

The Spring Mountains, particularly the area near Mount Charleston, are a hotbed of biodiversity, with an estimated 28 species of plants, animals and insects found nowhere else in the world, according to the U.S. Forest Service. The region’s high elevation, geographic isolation, cooler temperatures, natural history and relatively high annual precipitation have created multiple quasi-ecosystems unique from the rest of Southern Nevada—much like a real island.

“I’ve heard it equated to driving from Mexico to Alaska in the amount of ecozones you pass through, in just driving from the bottom of Kyle Canyon and hiking up to Mount Charleston,” said Katy Gulley, a wildlife ecologist for the U.S. Forest Service. “There’s that much diversity and vegetation changes.”

Anyone making the 40-mile journey from Las Vegas to the very top of Mount Charleston passes through four or more distinct ecological zones, depending on how you break them down, Gulley said.

At the bottom of the mountain is a zone known as the desert shrublands, where the primary vegetation is creosote bush, blackbrush and, especially in slightly higher elevation areas, Joshua trees. Keep going up and you’ll find the low conifer zone dominated by evergreen pinyon pine and juniper trees.

Further up still, in many of the most popular Mount Charleston hiking areas, is the high conifer zone, with ponderosa pine trees, white fir trees and bristlecone and limber pines, Gulley said. The bristlecone pine trees have the distinction of being among the oldest trees on earth, with a lifespan that can exceed 1,000 years, noted Patrick Donnelly, Nevada state director for the Center for Biological Diversity.

“Many places where the bristlecone pine occurs throughout Great Basin [have] sort of isolated trees, whereas on Mount Charleston, there is a legitimate bristlecone forest,” Donnelly said.

Finally, past the tree line at or above 10,000 feet and you enter the ultra-sensitive alpine zone. That region is home to some of the most unique species in the Spring Mountains, as they evolved in the most seclusion, Gulley said.

“You go up [the mountain], and it’s a totally different habitat,” noted local plant ecologist Hermi Hiatt. “It’s closer to the Great Basin vegetation, but there’s a big gap between the sky island and the Great Basin. That’s what’s kind of unique.”

Where endemic species thrive

Many of the endemic organisms—meaning they're found only in one place—that live on Mount Charleston and in the Spring Mountains have close relatives found elsewhere on earth. Nonetheless, their relative geographic isolation has created species-level differences over time.

The Mount Charleston blue butterfly is one of the most well-documented endemic species in the Spring Mountains and the only endemic species in the area that the federal government recognizes as endangered. But the tiny, hard-to-spot insect is just one of seven endemic butterfly species in the Spring Mountains, including another at-risk species known as the Spring Mountains dark blue butterfly, which is up for review for federal endangered status.

UNLV Life Sciences Professor Daniel Thompson has been studying both species of butterfly, which thrive high up in the mountains, since 2010. They are showing signs of recovery despite their critical status; Thompson spotted the Mount Charleston blue butterfly this July in the Lee Canyon area, where they had not been seen since the 1990s.

“Because of all the rain, (they’ve) had a fair amount of emergence,” he said, referring to this year’s unusually wet spring.

The area’s endemic butterflies have thrived for centuries in mutualistic relationships with flowering plants, some of which are also endemic, Donnelly said. Examples include Clokey’s thistle, rough angelica, Torrey’s milkvetch and the mountain oxytrope, the latter two on which the Mount Charleston blue butterfly feeds.

“Part of why there’s all these unique species of butterfly is also why there’s all these unique species of flowers,” Donnelly said.

Other species endemic to the Spring Mountains include the Mount Charleston ant and Palmer’s chipmunk. The chipmunk is relatively common in the mountain range, but the ant is notoriously difficult to find and identify, Gulley said.

“There’s not a lot of ant specialists out in the world that have been to the Spring Mountains, so it doesn’t have a lot of great information,” Gulley said. “But it has been identified and seen here and is not known to occur anywhere else.”

Preserving the sky island

Loss of biodiversity is an ongoing threat facing species and ecosystems worldwide, and the Spring Mountains are no exception. Tom Padden, who has lived in the town of Mount Charleston since the 1950s, says he has observed firsthand reductions in the overall health of the mountainous ecosystem.

“In the last 20 years, it’s become so evident to me the declines in the quality of the environment due to human impacts,” Padden said.

One species on the mountain range at risk is the ancient bristlecone pine trees, some of which were destroyed in the 2013 Carpenter 1 wildfire that blazed through almost 28,000 acres in the Spring Mountains. Given the slow growth of bristlecone pines and the fact that wildfires aren’t a natural part of their ecosystem, some of these trees still haven’t regenerated, Donnelly said.

Improving wildfire management practices will be crucial to protecting those trees and other plants and animals, Gulley said.

“As an agency, we’re moving toward better preparing the landscape to have less catastrophic wildfires,” she said.

Other threats include invasive species, irresponsible recreation and climate change. Although the mountain range experienced more snow than usual this year, the Forest Service and others have observed lower annual snowpack in recent years, a trend expected to continue because of climate change.

Snowfall enables some of the rare and endemic flower species to bloom, Donnelly said, and is the primary factor that differentiates Mount Charleston from the surrounding desert landscape. Snow also keeps the ground wet, thereby reducing the risk of wildfire.

The alpine sub-ecosystem is particularly vulnerable to ongoing and anticipated changes in snowfall and overall precipitation, Gulley said.

“It’s really those very high elevation species that are most impacted by changes in climate because they’ve evolved to be so specific to those conditions. Any changes up there in the alpine zone will really negatively affect those plants,” she said.

As the Mount Charleston area grows in popularity for recreational uses, Gulley emphasized that visitors should be careful not to bring in traces of invasive plants from their shoes or on car tires. They should also remain on trails, so as not to disturb nesting areas and habitats for rare species such as the blue butterfly.

Above all, visitors should be mindful of the fact that they’re entering a sensitive, region considered one of the most biodiverse parts of the southwest.

“It’s a really, really special place,” Donnelly said.

This story originally appeared in the Las Vegas Weekly.