Managing abandoned Mediterranean mountain landscapes: The effects of donkey grazing on biomass control and floral diversity in pastures

Abstract

Traditional Mediterranean Mountain landscapes in Spain have suffered dramatic environmental and social changes over the last seven decades. The loss of these landscapes has had consequences for biodiversity, soil erosion, landscape quality and ecosystem services as croplands and pastures were mainly converted into forests and scrublands. Many animal breeds present in traditional land uses such as the Catalan donkey (Equus asinus var. catalana), are also at risk of extinction, but can provide environmental services while recovering traditional landscapes. In Puy de Cinca, a village in mountainous northeast Spain, we studied how grazing by Catalan donkeys reduces pasture biomass and the effects on plant diversity in pastures. We used Sentinel-2 satellite imagery to calculate the Normalized Difference Vegetation Index (NDVI), a biomass sensitive spectral index, throughout the grazing period to monitor pasture biomass and compared it to pastures without grazing. We also calculated several plant diversity indicators in pastures with and without grazing donkeys. Furthermore, we studied land use changes over the last seven decades using old (1956) and current (2018) aerial images, with forest, agricultural lands, and trails interconnecting the village being mapped to understand landscape changes. The results indicated a great increase in the forested area (348.3 ± 17.0 ha). Meanwhile, a severe decrease in cropland area (73 %) and trail length (62.5 %) was also observed. Concerning the effect of donkey grazing, biomass was lower in pastures with grazing donkeys, with NDVI values decreasing once donkeys started grazing. Nevertheless, plant diversity was higher in pastures with grazing donkeys than in abandoned pastures. This study demonstrated the capacity of low-to-moderate-intensity donkey grazing to improve plant diversity and reduce biomass in pastures. Furthermore, the study of land use changes allowed an understanding of landscape dynamics, which can help address the social and environmental recovery of the village.