Habitat changes over 45 years on the small Mediterranean archipelago of the Medes Islands (Catalonia, NE Spain).
The small islands in the Mediterranean basin play an important role in its diversity because they have very unique natural habitats. They are very vulnerable to the direct and indirect effects of human activity, which severely impact ecosystems. Our study analysed the dynamics of the vegetation over recent years on one small island in an attempt to understand how the vegetation is changing and whether this is impacting the habitat diversity. The study was conducted on the Meda Gran, the largest island in the Medes Islands archipelago, which is located to the northeast of the Iberian Peninsula. A diachronic analysis was performed using the current vegetation cartography and a map published in 1984. Two dynamics were identified: the ruderalization caused by the overpopulated seagull colony and the natural succession of the vegetation. These processes have led to a loss of habitats on the island, such as the Astragalus tragacantha habitat, or on the contrary, the growth of populations of invasive species such as Opuntia ficus-indica. These patterns highlight the vulnerability of these small islands and the need for effective management to conserve these protected natural areas and their habitats.