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  Vernal Pools

California Vernal Pools

California Vernal Pools are small land depressions with impermeable hardpan subsoil.  These depressions are annually inundated during the wetter winter and spring months but dry out by the dry season.  A notable characteristic of vernal pools are the concentric rings of flowering plant species that develop as the water levels drop. 

Vernal pools are hosts to native plant and animal species that have evolved to cope with the extremes of this ecosystem. Two animal species that require Vernal Pools to complete their lifecycles are Vernal Pool tadpole shrimp (Lepidurus packardi) and fairy shrimp (Branchinecta spp.) which are federally listed as endangered and threatened, respectively.  These vernal pool species rely on the seasonal influx of water in these pools to complete their lifecycles.  The eggs laid by both of these species have a tough outer layer that protects the embryo from the hot and dry summer.  Soon after the rains have begun to fill the vernal pools, these species will hatch to feed and procreate before the pool dries.  As the vernal pools disappear due to human development, so do these specialized vernal pool species. 

For specific information on vernal pools and the plant and animal species they host see the links below.


California Dept. of Fish and Game (CDFG): http://www.dfg.ca.gov/education/newsletter/2005/vernalpools.html>

California Dept of Pesticide Regulation (CDPR):

U.S. Environmental Protection Agency (EPA):

Sacramento Valley, California Native Plant Society (CNPS): http://www.sacvalleycnps.org/Conservation/vernalpools/mather1.htm>

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