About the Antioch Dunes National Wildlife Refuge

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Tucked between the San Joaquin River and the City of Antioch, the 55-acre Antioch Dunes National Wildlife Refuge is the only federal wildlife refuge in the United States established for the protection of two endangered plants and an insect:

Antioch Dunes evening primrose (Oenothera deltoides howellii)
Contra Costa wallflower (Erysimum capitatum angustatum)
Lange’s metalmark butterfly (Apodemia mormo langei)

The refuge is made up relict sand dunes spread across two isolated parcels, the Stamm Unit and Sardis Unit, which are hemmed in like puzzle pieces between the former Fulton Shipyard to the west, the Kemwater Plant to the east, a retired sewage treatment plant and railroad tracks to the south, and the Georgia-Pacific Gypsum Plant in their midst.

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The Antioch Dunes National Wildlife Refuge was established by the United States Fish and Wildlife Service in 1980 to protect what little remained of this unique dune system that historically towered above the San Joaquin River’s banks. These ancient sands formed over the last 500,000 years by glacial action in the Sierra Nevada. As the resulting grains of sand flushed down creeks and rivers, they settled out of the water column and blew and washed ashore along the glacial-age floodplains. From there, prevailing summertime winds swept the sands east, accumulating along the banks of the San Joaquin River near present-day Antioch. Although such dunes might have repeatedly formed here five times or more, today’s dunes likely formed within the last 140,000 years. At their height, they towered some 120 feet above sea level, extended approximately 800 feet inland, and stretched more than two miles along the San Joaquin River’s southern bank.

Although the Antioch Dunes are completely isolated today, there were once connected by a lesser dune system that stretched from the foothills of Mount Diablo eastward to the banks of Marsh Creek, then south along the western edge of the Central Valley. Biologists theorize that some 5,000 to 8,000 years ago, desert plant and animal species worked their way northward from the Mojave Desert along arid habitat corridors such as these during dry, interglacial periods, eventually colonizing the Antioch Dunes.

Climate change and other natural processes, followed eventually by humankind’s agricultural practices, led to the gradual isolation of the Antioch Dunes. Left to their own, species such as Lange’s, the evening primrose, and the wallflower drifted away from their southern ancestors and evolved over time to become the localized endemic species we recognize today. These species distinctions are subtle, and some plants, like the Antioch Dunes buckwheat (Eriogonum nudum psychicola) have recently been recognized as distinct species.

Though they’ve been biologically isolated for millennia, the dunes have long been influenced by human habitation. Spanish explorers in the 1770s reported visiting Native American villages here. Later, under the Los Megaños Land Grant in the mid-1800s, settlers established Smith’s Landing—Antioch’s antecedent. Since then, several sand mines and brickyards, a piggery, dairy, sheep fold, vineyard, shipyard, paper mill, the Little Corral Bar, and a track field all have had their day.

The most destructive of all these activities were the brickyards and sand mines, both of which exhausted parts of the dunes down to their underlying hardpan. Following the 1906 earthquake, much of San Francisco was rebuilt with bricks of Antioch Dune sand and, later in the 1930s, sand was shipped to the horse tracks at Golden Gate Fields. The remnant dunes now reach heights of 50 to 80 feet at best.

Sand mining ceased the day before the refuge was officially established, but that wasn’t enough to protect the dunes. In 1986, six years after the refuge opened, limited staff, wildfires, and trampling forced the Service to restrict public access to the dunes.

Today, refuge biologists are working against the clock to protect the existing populations of Antioch Dunes evening primrose and Contra Costa wallflower, and to triage the precipitous decline in Lange’s metalmark butterfly numbers before this endemic species becomes extinct.

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One thought on “About the Antioch Dunes National Wildlife Refuge

  1. Mike Olson says:

    This beautiful refuge is so close by yet I’ve never heard much about it. Glad it is limited to public access and hope the butterfly and plants can survive the ravages of mankind.

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Lange's Metalmark Butterfly

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