Riparian buffer zones as elements of ecological networks: Case study on Parnassius mnemosyne distribution in Estonia

Territorial ecological networks (in US and some other countries known as greenways) are coherent assemblages of areas representing the natural and semi-natural landscape elements that need to be conserved, managed or, where appropriate, enriched or restored in order to ensure the favourable conservation status of the ecosystems, habitats, species and landscapes across their traditional range. An ecologically compensating areas network is a hierarchical system with the following levels: (1) core areas, (2) buffer zones of core areas, (3) corridors and stepping stones, and (4) nature development and/or restoration areas that support resources, habitats and species. Rivers form natural ecological networks and riparian buffer zones of rivers are typical elements of ecological networks. We studied the distribution of Clouded Apollo (Parnassius mnemosyne) and its habitat requirements in Estonia. Seventy-eight percent of all Clouded Apollo observations were recorded in riparian meadows along the banks of rivers with riparian strips consisting of bushes and trees. Detailed study showed that the butterfly is in most cases associated with meadows with a riparian strip of alder. This is the habitat of the food plant (fumeworth-Corydalis solida) of the larvae, the feeding and mating place of adults, and the migration and hiding site for the Clouded Apollo. The population area and number of individuals have been increasing during the last years, and a new growing South-Estonian sub-population of Clouded Apollo has also been discovered in Estonia.