The umbrella effect of Natura 2000 annex species spreads over multiple taxonomic groups, conservation attributes and organizational levels

The Natura 2000 network (N2K) was designed using species and habitats annexed in the European Union's (EU) Directives of Birds (BD) and Habitats (HD). The selection of such species receives increasing criticism, as does the frequent use of design methods not based on Systematic Conservation Planning (SCP). As a result, a proportion of the EU's biodiversity may remain uncovered by the network, irrespective of the degree of coverage of the annex species. Data limitations currently prevent rigorous EU-wide gap analysis for multiple biodiversity components simultaneously (i.e., taxonomic groups, conservation attributes and organizational levels), but regional data at finer resolutions may add evidence of the breadth of the umbrella effect to be expected. We tested the hypothesis that an objectively designed N2K may confer the EU ' s annex species an umbrella effect over multiple biodiversity components. This conjoint analysis of multiple taxa, attributes and levels is rarely done. We used distribution data of terrestrial vertebrates and invertebrates in one of the richest regions in the EU (Extremadura, Spain), whose reserves and biodiversity surpass many EU countries, and where the N2K was designed through SCP. We implemented a gap analysis explicitly including annex species status, conservation-relevant attributes (rarity, endemicity and vulnerability) and organizational levels (species, richness and hotspots). The annexed species acted as an umbrella group at the species, richness and hotspot levels, successfully covering rarity, endemicity and vulnerability. Our results show that the set of species that currently forms the EU's directives annexes has a wide umbrella potential, at least where objective SCP methods were used for reserve design. We suggest that, under such conditions, N2K design could essentially remain constant within a context of changing threat status, the challenge of conservation resting more on management measures than on redesigns of the network.