VERNAL POOLS
Vernal Pools
Vernal pools are naturally occurring, seasonal wetlands. They are essential for habitat preservation because none of the plant or animal species can flourish alone. This wetland habitat is a prime example why the environmental movement evolved from saving species to saving habitat. As with all things in nature, the plant and animal species that are part of a vernal pool habitat enjoy a wide range of size, color, and shape.
A vernal pool habitat exists in a mutually beneficial exchange with the nearby uplands (sage brush and mesa tops) which host myriad pollinators and propagators, including all the bugs that attract local and migrating birds. The vernal pool habitat includes an important chain of prey and predators.
Vernal pools exist as depressions in the boulder-filled, hard red clay. The hardpan, or clay liner, prevents rainwater from percolating through the soil. Vernal pools are temperature specific and the pools will only respond to a cold winter rain, never to an unseasonal warm rain. When the pools fill with cold winter rains, water ponds on the surface creating a temporary wetland that lasts only until it turns again to dust in the summer. Vernal means spring, and springtime is witness to a spectacular change of life forces. Eggs hatch and seeds germinate, leaving the pool vibrant with life and color. Fragile but hearty, the fairy shrimp eggs and some of the plant seeds are known to lie dormant for at least 14 years. As the dry summer approaches, the water evaporates or transpires, leaving the pool to dry until the next year. Frogs encase themselves in a natural sac that protects them from the dry clay of summer. The timpani of winter rain on the hard clay
awakens them, alerting them that it is time to emerge and renew the circle of life. Click here to listen to the vernal pool frogs at night.
Vernal pools turn from dust to vibrant pond life to a carpet of wildflowers, then back again to dust as the cycle flows from season to 
season throughout the year. The indigenous peoples who lived here made full use of the bounty of life existing in these natural habitats. There are 54 sensitive species identified along with common flora and fauna that share the vernal pool ecosystem. Many of the species are endemic, existing exclusively in this system and are, therefore, protected under section 404 of the Clean Water Act. San Diego CA vernal pools are part of the Riverside plate which is 400,000 years old. Only three percent of San Diego’s original pools remain. It is illegal to disrupt a vernal pool habitat. The Mira Mesa High School Ecology Club is proactive in their vernal pool studies, designing paths to direct foot traffic along side but not inside the fragile habitat.
Visit our Vernal Pool Gallery to get a better view of the pictures on this page. Clockwise from top left: 1, wet season vernal pool habitat ; 2, spadefoot toad; 3, mesa mint and fairy shrimp after the first rain; 4, dry season vernal pool habitat.; and 5, aerial view of vernal pools around Challenger Middle School in Mira Mesa, San Diego CA. [The photos shown in the gallery below are being upgraded, so please visit us again for crisper images.] Another excellent source for vernal pools is California Vernal Pools: Kids & Education.
61 Photos
Photos by Kathryn Wild and NAS Miramar Natural Resources Department. Species are enclosed in quotation marks when “Kumeyaay Native American names” are known. Botanic names are in italics. Common names are in regular type.
