Study area
With 3,200 km2 and a population of 4.5 million, the Barcelona Metropolitan Region (BMR) is one of the most densely populated regions in Europe (Fig. 4 ). However, this region still houses several important natural and semi-natural areas featuring considerable ecological diversity and valuable biocultural landscapes. Contrasting topography (elevation ranges from 0 to 1700 m a.s.l.) and climate (with gradients NE-SW from moist to dry and NE-SW from less to more continental) bring about a greater variability than that found in general Mediterranean conditions, which is responsible for the high biodiversity of this highly human-transformed territory. The region covers more than 40 habitat types of European interest (according to 92/43 EU Directive), including natural (forests, scrublands and grasslands; 60% of the region) and semi-natural habitats (croplands; 21%).
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