Dune slacks are low depressions between dune ridges and are close to, or even below, the water table. These low depressions in the hind-dunes are created by aeolian forces. In contrast to dune grassland habitats, dune slack vegetation forms on damp and almost level ground. As with the other dune habitats, pioneer/successionally-young dune slack habitat is becoming increasingly rare, succeeding to the more mature phases of slack development as the dune systems stabilise. The recognised dune habitats, and their reference and modified states, are described in the sections below.