Half of the European species have a stable population trend; about a quarter of them are declining and about one tenth are increasing. The threats to European dragonflies vary regionally and over time. During most of the twentieth century, large-scale land conversion, canalisation of rivers and water pollution (including eutrophication) were the main causes of decline, impacting especially species dependent on mesotrophic or running waters. Declines were particularly severe in Western Europe from the 1960s to the 1980s, when several species became extinct over large areas. Since then, improved water management and decreasing eutrophication have had a positive impact, and many of the species dependent on running waters have made a surprisingly fast recovery. Recently, there have been some indications that also species dependent on mesotrophic waters are starting to recover.
The conservation status of dragonflies in Central and Northern Europe has improved in recent decades, and is now generally considered to be good. In the Mediterranean region, the threats to dragonflies are, however, increasing rapidly. The smaller distribution areas of most Mediterranean dragonflies, combined with these increasing threats, make that most threatened dragonflies are currently found in the Mediterranean Basin. Fifteen out of the 22 threatened species are dependent on running water. All of these species are confined to the Mediterranean. They are impacted by the increasing demand for water for irrigation and for consumption by the growing (tourist) population, as well as by the increased frequency and duration of hot and dry periods. River species are adversely affected by the construction of dams and reservoirs as well as by desiccation and (to a lesser extent) deteriorating water quality. Species associated with smaller streams are declining due to desiccation caused by dry weather, fires and increased water extraction for local agriculture. Several of these species occur in small brooks and seepage areas which, due to their small size, can be destroyed by a local event, such as a fire, the construction of a house or the extraction of water by an individual farmer.