Temporary ponds, or vernal pools, are dry for part of the year, but fill with water when the rains come or when the snow melts. They can be tiny puddles or quite extensive areas, such as playa lakes, but because very few fish can survive in them they provide a unique habitat for a number of rare invertebrates and amphibians. In the UK, one in four woodland, old meadow and heathland temporary ponds contains Red Data species.

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