Wetlands occupy some six per cent of the Earth's land surface. They vary from fens and freshwater marshes to tropical mangroves and tundra swamps. They perform vital hydrological, chemical and biological roles and contain unique and diverse forms of wildlife and habitat. They are disappearing at an alarming rate and are threatened by both the direct and indirect effects of human activity. The purpose of this book of especially commissioned articles is threefold: (a) to explore the occurrence and composition of wetlands and their physical and biological dynamics; (b) to consider the impact upon them of agriculture, industry, urbanisation and recreation; and (c) to examine what steps can be taken to manage and to preserve their future survival.