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Wednesday, February 20 , 2019, 5:58 am | Fair 38º

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Sands of Time Continue to Change Guadalupe Dunes


Transformed daily by wind, waves and tides, a majestic masterpiece never looks the same way twice.



Guadalupe-Nipomo Dunes National Wildlife Refuge in northern Santa Barbara County is the largest, intact dune complex in the West. It’s not only pleasing to the eye, but a constantly shifting natural wonder, transformed daily by wind, waves and tides. The dunes are the tallest on the West Coast, with some topping 500 feet right out of the ocean.

How did such a massive dune ecosystem come to rest along California’s Central Coast? Its origins go way back, more than 12,000 years ago at the end of the last Ice Age.

I was recently standing atop 5,100-foot Cone Peak, located in the Santa Lucia Mountains along the rugged Big Sur coastline. Coastal fog hugged the lower peaks that plummeted to cascading creeks. It’s actually there where the formation of the dunes began and still evolves today. The range stretches down through San Luis Obispo County, eventually feeding the Santa Maria River mouth. The Cuyama and Sisquoc Rivers in Santa Barbara County also contribute to the Santa Maria River, which spews various rock deposits onto the beach between the Nipomo and Guadalupe Sand Dunes.

“The dunes are pretty recent for the most part,” stated Jeff Parsons, a geologist and earth scientist, speaking in geological terms. “There’s good dune definition over the last 10,000 years here.”

During the last Ice Age a new coastline was formed when the polar ice caps melted. The Santa Lucia Mountains received large amounts of rain at the end of this Pleistocene era. During these rains, streams carried large quantities of sediments over vast flood plains before depositing them along the coast. Eventually these sediments consisting of Franciscan rock complex that are 90 to 150 million years old and extensive Cenozic rocks — including Monterrey Foundation that are 67 million years old — were reduced by waves of rising oceans, grinding the heavier sediments to micro granules. Geochemical studies in the dunes indicate they’re enriched with phosphorous, an important element of soil fertility.

“The phosphorous probably originated from mineral matter eroded from phosphorous-rich portions of the Monterrey formation,” Parsons explained. “It’s a neat area out here, geologically.”{mosimage}

Once the sediments reached the shore and were crushed into sand particles, they were dispersed by prevailing northwest winds, crashing waves and swirling currents.  Waves and high tides pull sand offshore during stormy winter months. During the summer, sand is deposited back onto the beach where prevailing northwesterly winds spread the tiny grains into existing dune formations.

The long, sweeping and artistic ripples in the dunes develop during periods of high winds.  Swirling blasts of air move sand in many directions at the same time, giving the dunes an interesting appearance of chiseled ridges and fish hook-shaped crests and wind lines.

“The dunes are unstable,” Parsons said. "They’re constantly shifting.”

Within the dunes live 1,400 species of flora and fauna.  Dune vegetation has adapted to the harsh environment. The plants start their growth by trapping sand in its root system. Dune formation begins when wind blows dry sand landward from the beach.  Sand drifts accumulate around objects such as plants and driftwood that interrupt wind flow.  Once the sand moves inland from shore, dunes stabilize around plants.

Certain plants like the silver dune lupine (Lupenis nipomensis) and mock heather (Ericameria ericoides) are found in the stabilized dunes while growing larger.  Various plants growing next to each other can cover an entire dune.  The beach morning glory (Calystegia soldanella) is the first plant to colonize the dunes.{mosimage}

“Many of the plants found in the dunes have adapted to the harsh environment,” said Lauren M. Brown, a botanist who leads hikes for the Dunes Center, 1055 Guadalupe St. in nearby Guadalupe. “The silver lupine has adapted by using its tiny hairs to keep water inside its leaves.”

Other plants found in the smaller dunes or foredunes found closest to the ocean have adapted by growing lower to the ground to survive.  Some of these include purple sand verbena (Abronia umbellata), yellow sand verbena (Abronia latifolia) and beach evening primrose (Camissonia cheiranthifolia).

“These plants grow lower to the ground in open areas to stay out of the wind,” Brown explained.  “They’ve adapted to being buried and covered while surviving in a challenging environment.”

Spotting wildlife in the dunes can be difficult.  Most encounters consist of a mere blur from lupine to coreopsis tree, but various sets of tracks are clearly defined in the sand ranging from kangaroo rats and legless lizards to black bears and mule deer.  Some mornings appear as if there’s a race track of prints around the mounds of silver lupine and other dune flora.

“You may not see a lot of animals during the day,” said Chris Barr, a wildlife biologist for the U.S. Fish and Wildlife Service and the refuge manager of the dunes.  “Animals are exposed to predators out in the open, so they’re more active during the night.”{mosimage}

The back dunes of the refuge harbor 11 freshwater lakes that have helped wildlife adapt to life in the dunes.  This has enabled larger predators like bobcats, mountain lions, coyotes and gray foxes to survive in the dunes and prey upon smaller dune dwellers like the kangaroo rat, which utilizes its long, narrow feet to travel in the refuge.

Two unique critters that have adapted to the dunes are the California horned lizard and the legless lizard.  The latter uses its slender body to burrow under the thin layer of crust found in various regions of the dunes.  The horned lizard uses its hard shell to protect itself from the heat in the dunes.

“They don’t have to burrow very deep,” said Barr, referring to the legless lizard.  “The sand isn’t like a hard pack.”

So when you visit the refuge and venture out to the dunes and the northwest winds are filling your shoes with golden grains, take a moment and watch the sand blowing by. You’ll be witnessing dunes in the making.

For more information about the dunes, visit the Center for Natural Lands Management at www.cnlm.org.

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