Volunteers begin to unload trays of Gambel's watercress and marsh sandwort. (photo: USFWS)

One of the planting sites at Guadalupe-Nipomo Dunes National Wildlife Refuge. (photo: USFWS)

by Lois Grunwald, Ventura FWO
On a foggy dirt road, with fog shrouding the Guadalupe-Nipomo sand dunes, an all-terrain vehicle (ATV) with precious cargo sputters to life.

On board are trays of marsh sandwort (Arenaria paludicola) and Gambel’s watercress (Nasturtium [Rorippa] gambelii), federally-endangered plants that have all but disappeared from their native homes, the wetland habitats of coastal California.    

This particular journey began more than two years ago as U.S. Fish and Wildlife Service (Service) biologists Mark Elvin and Connie Rutherford, along with Refuge Manager Glenn Greenwald, worked with dozens of partners, including academic, government, and private organizations, to carefully craft a plan to grow and outplant these two critically endangered species in dunes swales in wetland areas at the Guadalupe-Nipomo Dunes National Wildlife Refuge. The goal is to establish new populations to prevent the extinction of these two plants and to aid in their recovery.    

In all, over 600 plants were planted at eight sites by approximately two dozen volunteers, including Service and California State Parks staff and students from California Polytechnic State University, San Luis Obispo. The volunteers arrived at the dune swales—located in valleys between the dune ridges—aboard the ATVs, as rough pathways snaking through dune scrub are the easiest access to the remote sites, which receive few visits from the public.  

One of the areas is simply called “Northern Wetland,” and another, “Snakebite Pond.”   All of the sites are wet or have shallow water of varying levels that is derived from groundwater underneath the dunes.   The wetlands are a tangle of willows, rushes, and sedges that harbor, among other animals, the Pacific tree frog and threatened Californiared-legged frog.   The sites are cordoned off by fences installed by the refuge to protect the plants from feral pigs, the occasional refuge visitor, and cattle that might penetrate the refuge’s perimeter fence.

Gambel’s watercress and marsh sandwort once occurred in coastal areas from the State of Washingtonall the way to Southern California. Now Gambel’s watercress only exists in one native location in northern coastal Santa BarbaraCounty. Until the recent plantings, marsh sandwort only occurred naturally at OsoFlacoLakeat Oceano Dunes State Vehicular Recreation Area. One population was introduced at Sweet Springs Marsh in MorroBay.   The plants are imperiled by development of coastal lands, an excess of nutrients which causes explosive growth of competing plant species, such as common watercress, willows, and cattails, hybridization with common watercress, and alteration of the hydrological regimes.

Guadalupe-Nipomo Dunes National Wildlife Refuge is located along the central coast of California in San Luis Obispo County. It is bordered by the Pacific Ocean to the west and farmland to the east and encompasses one of the largest coastal dune systems remaining in California.

The refuge protects breeding habitat for the endangered California least tern and the threatened western snowy plover. The refuge also provides habitat for other endangered and rare species, including the California red-legged frog, and plant species, including the federally-endangered La Graciosa thistle (Cirisum loncholepis). The refuge contains healthy populations of mule deer, bobcat and mountain lion, as well as large flocks of wintering shore birds and waterfowl.  

A few weeks after planting marsh sandwort and Gambel’s watercress at the dunes, the plants are doing very well, according to Mark Elvin, biologist for the Ventura Fish and Wildlife Office.

California Polytechnic State University graduate student Carlos Torres will be studying the two plants to help further the Service's understanding of these species’ habitat requirements.  The information gleaned from this pilot project will aid the Service in finding additional locations suitable for recovery of the rare plants, insuring that the public can continue to enjoy the diversity of plant life within the Guadalupe-Nipomo Dunes ecosystem.

“We are thrilled that so many diverse partners can bring together their talents on this long-term project to further conservation and recovery of these two extremely rare plants on the Guadalupe-Nipomo Dunes National Wildlife Refuge,” said Greenwald.

“This has been one of the most rewarding projects that I have been involved in during my career with the Service,” said Elvin. “It is gratifying to have a partnership working to conserve these critically endangered species.”

(Michael Woodbridge, Hopper Mountain NWRC, contributed to this report.)