Our smallest ecosystem
San Diego’s vernal pools are fleeting water bodies that fill up during rainy years, and then vanish later in the season. These miniature ecosystems host numerous rare and endangered species. There are about 2,591 vernal pools in the city of San Diego, and about 600 of those are protected in city-run preserves. Others occur on Marine Corps Air Station Miramar, in San Marcos and Ramona.
Migratory birds
Ducks, geese and shorebirds visit the pools to dine on fairy shrimp and other crustaceans.
Even rarer than its San Diego cousin, this endangered herb is found only in a handful of vernal pool complexes in Otay Mesa, just north of the border.
Otay Mesa mint
This endangered annual grass grows near vernal pools, from San Diego to Ventura. Its bright green, aromatic foliage secretes a sticky, bitter substance.
Orcutt grass
A flowering grass with white or purple blooms that sprouts around vernal pools. It’s federally threatened, and grows only from San Diego to San Luis Obispo.
This squat toad grows to about 2 1/2 inches long, with skin in shades of tan, green or gray. It lives most of its life on land, but enters vernal pools to breed.
San Diego Mesa mint
This sweet-smelling endangered herb sprouts purple, bell-shaped flowers and grows only in San Diego County.
Spreading Navarretia
This endangered annual herb pops up at vernal pools, where its spiky leaves are a favorite snack of rabbits and other herbivores. It’s found only in San Diego, Murietta and Santa Ana.
Button celery
Western spadefoot toad
This endangered crustacean lives only in vernal pools between San Diego and Ventura. Its translucent body is less than an inch long, and it swims upside down in the pools. Its cysts can lie for decades in the soil before hatching.
Riverside Fairy Shrimp
A endangered crustacean that lives only in vernal pools in San Diego and Orange Counties. Its cysts lay buried in soil for years or decades, and hatch during wet years, usually at a different time period than the Riverside fairy shrimp.
San Diego Fairy Shrimp
UT
MICHELLE GUERRERO
Sources: U.S. Fish and Wildlife Service; California Department of Fish and Wildlife; San Diego Zoo Institute for Conservation Research; Calflora
Western spadefoot toad
Western spadefoot toad
Even rarer than its San Diego cousin, this endangered herb is found only in a handful of vernal pool complexes in Otay Mesa, just north of the border.
Otay Mesa mint
San Diego Mesa mint
This squat toad grows to about 2 1/2 inches long, with skin shades of tan, green or gray. It livesw most of its life on land, but enters vernal pools to breed.
