20 years of changes in the biodiversity of birds and butterflies in the Metropolitan Region of Barcelona

Abstract

This article analyses the state and trend of biodiversity in the Barcelona Metropolitan Region (RMB) for twenty years (2002-2022), using standardised data from two different taxa, birds and butterflies, which are effective bioindicators of habitats, ecosystems and landscapes changes. These groups are widely used, both in Catalonia and in Europe, in biodiversity monitoring networks based on citizen science. The article examines the population trends of these groups in relation to the legal protection, thus providing relevant information on the effectiveness of the protection of natural areas for the conservation of biodiversity. In the last 20 years, the RMB has seen a stability in bird populations, except for those that inhabit natural open spaces. In contrast, butterflies have experienced a decline, particularly in protected areas, with a noticeable loss of specialist species. This reflects possible habitat deterioration. Protected Areas, intended for the conservation of biodiversity, have not improved the situation of birds or butterflies.