Endangered Contra Costa Goldfields Vulnerable to Agricultural Practices

by Doreen Smith, Marin CNPS Rare Plant Co-Chair, Vernon Smith, Marin CNPS Website, and Ann Elliott, Marin CNPS e-Newsletter Editor

In May 2002, Betty and Jack Guggolz, members of Sonoma County’s Milo Baker CNPS Chapter, discovered a large population of Contra Costa goldfields, Lasthenia conjugens (CNPS List 1B.1 and Federally Endangered) in a sheep pasture immediately east of Highway1 in north Marin County bordering Sonoma County at the Estero Americano. The site, a seasonal wetland, floods in wet rainfall years.

Randall Morgan, CNPS Fellow and noted Santa Cruz naturalist, confirmed the population in May 2003. He noted the location correctly and reported the population to Doreen Smith, Marin Chapter Rare Plant Co-Chair. A few days later, Doreen photographed it and, by reaching through the fence, collected a sample for the California Academy of Sciences Herbarium for their collection (see below).

In July 2020, Doreen happened to be driving along this section of Highway 1 and saw trucks on the site spreading dairy manure slurry across the pasture (see photograph at bottom). Much of the Lasthenia conjugens population may not survive this nitrogen-rich slurry or any subsequent disking if the pasture is converted to silage production. The owners of the land may not even know that they had a national treasure in their pasture.

Contra Costa Goldfields was listed as Federally Endangered in 1997. In 2006, one area was identified as its Critical Habitat near Hercules north of Richmond. Federally “Endangered” means a species is in danger of extinction throughout all or a significant portion of its range. California Rare Plant Rank 1B indicates that the plant is rare, threatened or endangered in California and elsewhere. Threat Rank 0.1 indicates that it is seriously threatened in California (over 80% of occurrences threatened / high degree and immediacy of threat).

Any development of this pasture requiring county, state, or federal approval would have had to identify any listed species and propose avoidance or mitigation plans. A change in agricultural practice does not require such governmental approval, so the impact of manure slurry on these goldfields is exempt from those mitigation requirements. Time will tell whether or not Contra Costa goldfields has suffered a significant setback.

Lasthenia conjugens hb

A carpet of Lasthenia conjugens (Contra Costa goldfields) in May 2003.

Lasthenia conjugens cu2b

Close up of Lasthenia conjugens (Contra Costa goldfields)

Lasthenia conjugens Field IMG 9551cm

Trucks spreading a manure slurry on top of the site of the Lasthenia conjugens on July 24, 2020.

Photos by Doreen Smith