Freshwater marshes are found throughout California, occurring in many different climates and elevations. They typically occur in nutrient-rich mineral soils that drain slowly and are waterlogged or saturated for most or all of the year. Freshwater marsh plant communities are characterized by the presence of emergent hydrophytes (plants adapted to growing in saturated soils and standing water) including rushes, sedges, cattails and grass species. Many of these species are rhizomatous (spreading from underground horizontal stems) and can tolerate growing in low oxygen conditions characteristic of saturated soils. Some freshwater marshes are vernal, filling with winter and spring rains and drying out in the summer. Freshwater marshes reduce destructive flooding, decrease waterborne pollution and support many species of resident and migratory animals. Despite these benefits to society and the environment, more than 90% of freshwater marshes in California have been destroyed due to filling with soil, draining, overgrazing or conversion to non-native species.