Salt marshes are middle to high latitude intertidal wetlands of great value. They play a major role in coastal defense, wildlife conservation, and as a key sink/source of organic material and nutrients, and are vitally important for a wide range of marine communities. Salt marshes also function as a sink for pollutants that would otherwise damage the surrounding environment. They also represent important historical and scientific archives. However, the majority of them are increasingly threatened by direct (e.g., land reclamation, groundwater extraction) and indirect (e.g., the so-called “coastal squeeze”) human actions, or by the effects of climate change. Indeed, salt marsh habitats have shrunk to half their historical coverage in the last century, and the enhanced sea level rise will be responsible for the loss of 60%–90% of today’s salt marsh areal coverage in the near future, according to whether or not effective measures to limit greenhouse gas emissions are undertaken. Local, small-scale solutions, such as barriers and fences, can be effective only on a short-term perspective or when dealing with immediate risk. Managed realignment techniques that require the landward retreat of coastal defenses and the subsequent tidal inundation of previously claimed agricultural land are actions that ensure the survival of existing salt marshes (or the creation of new ones) over a longer temporal period. However, only the transition to a global model of development that is environmentally sustainable can ensure the persistence of salt marsh habitats and the maintenance of ecosystem services that they provide.