A salt marsh is a type of marsh that is a transitional intertial between land and salty or brackish water (e.g., sloughs, bays, estuaries). It is dominated by halophytic (salt tolerant) herbaceous plants. Historically, salt marshes have sometimes been treated as "wastelands", along with other wetlands. We now know that salt marshes are one of the most biologically productive habitats on the planet, rivaling tropical rainforests. This is partly due to the daily tidal surges that bring in nutrients, the natural chemical activity of salty (or brackish) water, the tendency of nutrients to settle in roots of the plants there, and the tendency of algae to bloom in the shallow unshaded water. Salt marshes also provide a benefit by protecting against severe weather, such as in the North American Gulf Coast. In the past, substantial areas of saltmarsh have been reclaimed as agricultural land and for urban development, but in the US and Europe they are now accorded a high level of protection by the Clean Water Act and the Habitats Directive respectively. There is growing interest in restoring salt marshes, through managed retreat or through the reclaimation of lands used for other purposes by salt marsh vegetation.