Current SDecies Status: This plan addresses six vernal pool species that are
listed as endangered and one that is proposed for threatened status: Eryngium
aristulatum var. parishii (San Diego button-celery), Orcuttia calfornica
(California Orcutt grass), Pogogyne abramsii (San Diego mesa mint), Pogogyne
nudiuscula (Otay mesa mint), Riverside fairy shrimp (Streptocephalus woottoni),
San Diego fairy shrimp (Branchinecta sandiegonensis), and Navarretiafossalis
Pogogyne abramsii was listed as endangered on September 28, 1978. Pogogyne
nudiuscula, Orcuttia ca1~fornica, Eryngium aristulatum var. parishii, and the
Riverside fairy shrimp were listed as endangered on August 3, 1993. The San
Diego fairy shrimp was listed as endangered on February 3, 1997. Navarretia
fossalis was proposed for listing as threatened on December 15, 1994.
Historically, San Diego, vernal pool habitat probably covered no more than 6
percent ofthe county, approximately 520 square kilometers (200 square miles).
Currently levels estimate a loss of vernal pool habitat in the San Diego County
around 95 to 97 percent because ofintensive cultivation and urbanization (Bauder
and McMillan 1998). Lack ofhistorical dataprecludes the same depth of analysis
for Los Angeles County, Riverside County, Orange County, or San Bernardino
Counties, but losses are considered nearly total (USFWS 1993). The current
distribution ofpools in northern Baja California, Mexico, probably comes much
closer to the historic condition (Bauder and McMillan 1998).
Habitat Requirements and Limiting Factors: Following winter rainstorms,
vernal pools form in depressions above an impervious soil layer or layers. Water
evaporates from these pools during the spring and early summer. Vegetation
communities associated with adjacent upland habitats that surround the vernal
pools in southern California are valley needlegrass grassland, annual grasslands,
coastal sage scrub, maritime succulent scrub, and chaparral.
Prior to 1945, the primary threats to southern California vernal poois were
grazing. water impoundments, and conversion to agriculture. In recent years,
urbanization and construction of infrastructure have resulted in losses of habitat
estimated to be as high as 97 percent. Urbanization can directly impact pools
through elimination of the habitat by soil alteration, vegetation alteration,
alterations in hydrological regimes, and water quality. Where pools remain th