Vernal Pool

A vernal pool, also called a vernal pond or ephemeral pool, is a seasonal pool of water that fills for part of the year and dries out for the rest, forming a distinct wetland biome. Because the pool does not hold water year round, it typically cannot support fish, which makes it a comparatively safe place for amphibians and insects to breed without the predation and competition fish would bring. A few tropical fish lineages, such as some killifish, have adapted to survive the dry season anyway, but they remain the exception. Vernal pools appear inside many different surrounding landscapes, including deciduous forest, grassland, pine forest, oak woodland, sagebrush steppe, coastal scrub and prairie. They are best known from Mediterranean climates, where the wet winter and dry summer pattern suits their cycle, but pools of the same kind occur in many other climates worldwide.