In many countries, saltmarshes represent a diminishing resource that threatens both natural changes and human activities. Suggestions that the rate of sea-level rise may accelerate, combined with a possible increase in mid-latitude storms, have raised concerns that the rate of saltmarsh loss may also accelerate, and that existing sea defences may be placed under even greater pressure. Saltmarshes are of increasing interest to a wide range of environmental scientists, engineers, conservationists, and planners concerned with coastal zone management. They are especially keen to understand the basic physical and biological processes which govern the formation and development of saltmarshes. Coastal engineers need to predict the likely effects on adjacent saltmarshes of abandoned or set-back of sea walls, and the impact of development schemes such as tidal barrages and marinas. Seven leading scientists present an overview of the most important questions including geomorphology, ecology, conservation and engineering significance.