Vernal pools, also called vernal ponds or ephemeral pools, are seasonal pools of water that provide habitat for distinctive plants and animals. They are considered to be a distinctive type of wetland usually devoid of fish, and thus allow the safe development of natal amphibian and insect species unable to withstand competition or predation by fish. Certain tropical fish lineages have however adapted to this habitat specifically.
Vernal pool with clay hardpan bottom, Vina Plains Nature Conservancy Preserve, California, United States
Vernal pool flowers, with different species occurring in zones related to soil moisture and temperature gradients formed as the pool dries out. Sacramento National Wildlife Refuge, Calif.
Vernal pool in northern California
A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently for years or decades or seasonally for a shorter periods. Flooding results in oxygen-free anoxic processes prevailing, especially in the soils. The primary factor that distinguishes wetlands from terrestrial land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique anoxic hydric soils. Wetlands are considered among the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal species. Methods for assessing wetland functions, wetland ecological health, and general wetland condition have been developed for many regions of the world. These methods have contributed to wetland conservation partly by raising public awareness of the functions some wetlands provide. Constructed wetlands are designed and built to treat municipal and industrial wastewater as well as to divert stormwater runoff. Constructed wetlands may also play a role in water-sensitive urban design.
Marshlands are often noted within wetlands, as seen here at the Jamaica Bay Wildlife Refuge in New York City.
Sunrise at Viru Bog, Estonia
Wetlands contrast the hot, arid landscape around Middle Spring, Fish Springs National Wildlife Refuge, Utah
Humid wetland in Pennsylvania before a rain.