The demand for sand and gravel in the UK has grown steadily since the 1920s, falling back only in World War II and the early 1980s. There are now probably about 15,000ha of worked-out flooded sites and 400ha to 500ha are added to this total each year. Much wetland wildlife has benefited, including a number of scarce plants and several species of dragonfly such as the Keeled Skimmer, Orthetrum coerulescens.