Practical insights to select focal species and design priority areas for conservation

Abstract

The focal species approach claims that a landscape managed for the conservation of a set of focal species, each of which identified as the most threatened by specific processes, also protects all the other species. We investigated the effects of two practical issues of this approach: the problems with identifying the species most affected by threatening processes, which often only target the most area-limited species, and the disregard for the different spatial scales at which processes affect different species. We focused on a fragmented landscape in Northern Italy and selected the most area-limited (Capreolus capreolus) and dispersal-limited (Muscardinus avellanarius) mammal species. We mapped and overlapped the suitable areas for the two species considering 2 suitability scenarios. We then evaluated whether the area-limited species was more effective as a surrogate for the dispersal-limited species, or the opposite held true (a surrogate is a species able to cover at least 50% of the area and the number of patches suitable for another species). Moreover, we evaluated if buffering the suitable areas for the two species with 4 buffer sizes affected their ability as surrogates. Neither the area-limited, nor the dispersal-limited species was found to be an effective surrogate for the other species because of the very different distribution patterns of their suitable areas. Conversely, when buffers around suitable areas were designed, the dispersal-limited species acted as a surrogate for the area-limited species in 7 out of 8 cases (2 suitability scenarios per 4 buffer sizes), while the area-limited species was a surrogate in only one case. Using area-limited species as focal species may thus be detrimental and lead to conservation plans unable to protect species for which the area is not the key factor affecting the distribution pattern. Conversely, when the suitable areas are buffered, dispersal-limited species could become effective focal species.