Reintroduction is the deliberate release of animals or plants into the wild with the purpose to enhance populations that have all but disappeared. Introduction of exotic species is outside the notion of reintroduction. Reintroduction programmes usually involve species which enjoy broad-based support in the population. If there is a chance for a species to return spontaneously, reintroduction is not considered. Reintroduction programmes require approval by the Ministry of Agriculture, Nature and Food Quality. Reintroduction of endangered fish species only requires approval by the Ministry as long as these species are not referred to in the 1963 Fisheries Act.
Reintroduction of local species, also referred to as re-establishment, involve reintroduction of species in areas where they do not or no longer occur, although they are found in other parts of the country. Instances of local reintroductions of plants are eelgrass, mountain arnica, juniper, black poplar and various field weeds.
Reintroduction happens if certain conditions are met. These conditions are laid down in the Policy regarding the Reintroduction of Animals issued by the Ministry of Agriculture, Nature and Food Quality.
Data on raven, stork, tree frog, scarce large blue, dusky large blue and small pearl-bordered fritillary are based on the counting grids of the Network Ecological Monitoring. Data on the beaver population are based on the Beaver work group of the Dutch Society for Mammal Studies and Mammal Protection. All nature statistics, e.g. the counting grids butterflies, breeding birds and amphibians are financed by the Ministry of Agriculture, Nature and Food Quality and the Ministry of Economic Affairs.