Managing habitats correctly is the key to saving Europe's most threatened butterflies, new guidelines have revealed.
Butterfly Conservation Europe has published a list of "do's" and "don'ts" for conserving 29 species listed on the EU Habitats Directive - European guidelines protecting wildlife.
Two of these species - the Large Blue and the Marsh Fritillary are found in the UK.
The new report provides crucial information on how to conserve these species and acts as a guide for EU countries to help meet international biodiversity targets.
Almost 10% of European butterflies are threatened with extinction. A report on population trends of grassland butterflies revealed the abundance of 17 typical grassland species declined by over 70% in the last 15 years.
These declines are driven by habitat loss and incorrect management. Many habitats are either abandoned from agriculture, allowing them to become overgrown with scrub, while others are too intensively managed.
The new guide will help ensure remaining habitats on key sites are better managed.
Lead author, Chris van Swaay of Dutch Butterfly Conservation said: "Managing habitats in the correct way is the single most important issue affecting the survival of European butterflies.
"This is the first time that practical information has been brought together to address the issue. We hope the advice will be taken up urgently across Europe to help save these species from extinction."
The report - "Dos and don'ts for butterflies of the Habitats Directive of the European Union", includes detailed accounts of species, their habitat requirements and food-plants and a list of dos and don'ts in the management of their habitats.
The Large Blue has been re-introduced to parts of Somerset following a UK-wide extinction in the 1970s.
Key "Dos" for the Large Blue state the importance of managing grassland by grazing to create the open conditions favoured by the species, but the guide also warns against overgrazing sites in mid-summer.
Dr Martin Warren, chief executive of Butterfly Conservation, said: "Butterflies are valuable indicators of the health of the environment. If we get the management right for butterflies, hundreds of other species will benefit and ecosystems will flourish."
Other guidelines for the 29 species include managing habitats for variety, the need for active woodlland management and desire for regular species monitoring.
Butterfly Conservation Europe is an umbrella group aimed at halting the decline of butterflies, moths and their habitats across Europe.
The report was published as an "Applied Conservation" paper in the newly launched open-access journal Nature Conservation.