Marshes, both tidal and non-tidal, are productive and complex ecosystems. The water in these systems ranges from fresh, to brackish, to saline as one moves from inland to coastal areas. Marshes are an interface between upland and aquatic habitats. In this book, the authors present current research in the study of the ecology, management and conservation of marshes including the climatic roles of marshes; the mesocosm marsh ecology of two south-western Spanish estuaries; factors conditioning the vegetation in the salt marshes of the Atlantic Coast of the Iberian Peninsula; and nutrient cycling in salt marshes.