This guide deals with the semi-natural woodlands dominated by alder, willows and birch that are found locally throughout Britain on wet and poorly-drained soils. Based on survey information from the former Nature Conservancy Council there are estimated to be 25,000–35,000 hectares of ancient semi-natural woodland of this type. In addition many more recent seminatural wet woodlands occur as part of successions from wetland and aquatic habitats.
By their nature these woods occur mainly as small woods or localised patches in larger woods. They are typical of river valleys, the surroundings of mires and raised bogs, the transition zones between open water and drier ground, and beside small winding streams. They can also occur on flushed slopes well above valley bottoms and on plateaux where a high watertable is maintained throughout the year. Typically, they have been managed as coppice in the past, but have been neglected or used as pasture recently. Many have been lost during the course of drainage work on watercourses and surrounding farmland.
