Background The marsh fritillary butterfly (Euphydryas aurinia) has undergone rapid decline in Denmark due to the fragmentation of its habitats and populations. Together with a continuing decline in the quality of existing and potentially suitable habitats, the marsh fritillary is now considered an endangered species. Only eight small sub-populations remain, and it is crucial to reverse this negative trend if the butterfly is to continue to exist in Denmark. Objectives The overall objective of the LIFE-ASPEA project was to bring the threatened and isolated population of marsh fritillary (Euphydryas aurinia) in Denmark into a favourable conservation status. In order to reach this objective, the project aimed to: Preserve and strengthen existing subpopulations through a range of conservation measures. Each subpopulation should be stable or increasing and have a minimum size of 500 individuals or approximately 125 observed spins. Create opportunities for the establishment of at least three new subpopulations from the existing localities through restoration of potential habitats. Raise awareness of the marsh fritillary amongst land users to ensure appropriate management of its habitats in the future. Results The project achieved its overall objective of attaining a favourable conservation status for the endangered of the target species through the strengthening of habitats: it secured more than 500 ha of existing and potential marsh fritillary butterfly habitats in favourable condition within three Natura 2000 sites, boosting survival prospects of the population in northern Jutland. In the short term, the number of larval webs in the four-year period of the project has doubled and four new subpopulations at Bruså, Napstjert Mose, Napstjert Enge and Strandby have been added. The project also improved the understanding of the species’ ecology and dynamics, distributing this information to around 500 landowners and civil servants responsible for caring out nature restoration. Awareness-raising among the involved landowners as well as the general public formed a substantial part of the project. It is important for the success of the marsh fritillary butterfly conservation work to engage these groups in the process. In particular, the project held meetings and excursions with direct contact between landowners, NGOs, the general public, politicians and administration officers. The project website, layman’s report, newsletter and pamphlets have helped stimulate interest and furthered participation in the conservation work. Finally, the project serves as a good demonstration of restoration followed up by recurring activities such as grazing. The project activities have also been included in a Code of Best Practice. Further information on the project can be found in the project's layman report and After-LIFE Conservation Plan (see "Read more" section).