A wetland is an area of land that is either covered or saturated with water for all or part of the year. Depending on how a wetland formed and the types of vegetation it supports, specific wetlands may also be called swamps, marshes, bogs, vernal pools, fens, or other names. In California, most of our wetlands are marshes.Wetlands support an astounding number and diversity of species. Across the U.S., over one-third of threatened and endangered species live exclusively in wetlands and almost half of all listed species depend on wetlands for at least part of their lives. In California specifically, wetlands are critical for many migratory and resident birds, fish, mammals, reptiles and amphibians. Learn more about the importance of California’s Central Valley wetlands in our storymap.