Winners and losers of landscape changes over the last sixty years in one of the oldest and southernmost national parks of the European Alpine region: Ordesa and Monte Perdido

Abstract

Traditional land-use decline in Mediterranean mountains is translating into extensive forest recovery and the loose of “cultural landscapes”. In this context, the management of semi-natural ecosystems plays a fundamental role for the future preservation of species and processes, particularly in protected areas, and managers need rigorous information for an integrative interpretation of the long-term and complex effects of land cover replacement. Here we analyze changes in the land cover structure of the Ordesa and Monte Perdido National Park and its peripheral protection zone, by comparing 7 types of patches from aerial photographs taken in 1956 and 2015. Then, we discuss how this process affected landscape diversity and two kinds of potential vulnerable plants. We found higher changes in the unprotected than protected areas, concentrated below the treeline in both cases, as a result of forest densification and strong reduction of anthropic and unvegetated areas. Total edge of patches decreased, as well as the number of patches, whereas mean patch size increased, indicating that patches merged and ecotones reduced. Shannon diversity index of the landscape decreased too, confirming a simplification of the system. Most Pyrenean endemic plants and threatened ones occur either on stable grasslands over the treeline, “winner” forests, or as rocky specialists irrespective of the land cover class. Therefore, past landscape changes do not seem to have affected them negatively, and forest expansion could also benefit several plants and tree-dominated communities at the south limit of distribution (Abies alba, Fagus sylvatica, Pinus uncinata). Landscape simplification, however, translates into plant diversity reduction too, which could be slowed down by creating or keeping small open patches inside matrices of forest. Maximization of plant diversity would require in this case some human perturbation, but at lower intensity than in the far past, in order to preserve large stands of old forests too.