Effectiveness of a large reserve network in protecting freshwater biodiversity: a test for the Iberian Peninsula

Although coverage by protected areas is increasing worldwide, their capacity to protect freshwater biodiversity is uncertain. This may be the case of the European Natura 2000, the world's largest reserve network, given its primary focus on terrestrial biodiversity. We tested this hypothesis by assessing the effectiveness of Natura 2000 in protecting freshwater biodiversity and associated key ecological processes in the Iberian Peninsula, where more than 25% of land is under some kind of protection. We compiled distributional data on 91 species of freshwater fish, amphibians and aquatic reptiles, at the subcatchment scale (c. 20km(2) resolution), for the whole Iberian Peninsula, and assessed the proportion of their ranges covered by Natura 2000. We also explored the coverage of the main environmental gradients, and the capacity of Natura 2000 to offer protection against human impacts. To do so, we evaluated land-use intensity and the human footprint within and upstream of protected areas, both of which might compromise the protection of biodiversity. Finally, we also analysed the incidence of reservoirs within and downstream of protected areas. Natura 2000 broadly covers the main environmental gradients in the Iberian Peninsula, but fails to provide sufficient coverage of freshwater biodiversity, with <20% of the range of species covered on average. This would be insufficient to achieve a modest conservation target of 25% of the range for more than 80% of species, including most of species specifically listed in the legislation. Moreover, although the network tends to comprise areas with the least human impact, it seems to be vulnerable to the propagation of upstream effects (intensive land use downstream) and the loss of downstream connectivity (reservoirs). Large reserve networks, primarily designed to protect terrestrial biodiversity, may not offer adequate protection for freshwater biodiversity. We recommend revisiting the design of Natura 2000 to improve the representation of freshwater biodiversity and enhance its capacity to address threats and particular ecological needs, such as for migration. Given the high pressure on land and the poor condition of the remaining unprotected habitat, conservation efforts must minimise the conflict of interest and management costs.