Background The Marsh fritillary butterfly (Euphydryas aurinia) was last observed in Schleswig-Holstein in 1991. The decline and eventual extinction of the species in the region was caused by a range of factors including intensification of land use, draining of bogs, and overgrowth of tall grass, scrub and brambles on military sites following the replacement of tanks by wheeled vehicles. Objectives The overall objective of LIFE+ Aurinia project is to reactivate habitats of the marsh fritillary in the last two known sites of the species (Nordoe and Jardelunder Moor). At similar good sites (e.g. the military training field Lütjenholm and Geltinger Birk) the project will try to improve the necessary habitats of the target species: mat grasslands, wet grasslands, heathlands and dry grasslands. At the remaining proposed project sites it may be possible to reintroduce the species in approximately 20 years when conservation actions have enabled the reactivation of the necessary vegetation. The condition of the sites varies according to the demands of the species, and therefore different actions are planned. The IUCN criteria for reestablishment of species were checked and influenced the planning process of the proposal. Expected results: Reintroduction of the marsh fritillary at the four most-improved of the eight project sites; Establishment of eight sub-populations of 100 individuals each at these four sites; Improvement or reintroduction of relevant habitat types through the following actions: conversion of 16 ha of spruce plantations; improvement of 40 ha of former agricultural areas into species-rich grasslands by hay/seed transfer and planting target plants (80 000 individuals); introduction of grazing on an area of 110 ha; Introduction of new conservation measures to Schleswig-Holstein: fire management; improvement of grassland by hay transfer; and large-scale rearing and planting of rare plants; Involvement of military and military-site managers and the establishment of co-operation for a more conservation-oriented site management.