Regional biodiversity conservation projects enhance stoat populations in agricultural landscapes

Regional biodiversity conservation (RBC) projects, encompassing landscape-scale agri-environment schemes (AES) and other governmental or non-governmental nature conservation initiatives, aim to counteract biodiversity loss in rural areas. Many such projects target specific species, for instance stoat ( Mustela erminea ). While studies have examined the impact of landscape-scale AES, the effectiveness of other RBC project types, particularly in promoting small mammals, has rarely been assessed quantitatively. Despite a lack of scientific evidence, expert-based views suggest that collaborative, coordinated landscape-scale conservation projects that consist in installing suitable micro-habitat structures are effective tools to promote biodiversity in general and stoats in particular. This study tested whether the relative abundance of stoats differed between sites with and without RBC projects. Using a paired design, 28 study sites distributed across 14 regions of the intensively farmed Swiss Plateau were compared. All the RBC projects had in common a targeted deployment of small structures, such as branch and stone piles, aiming at supporting stoat populations. Stoat abundance was estimated using a combination of three methods: scat collection with trained detection dogs, direct visual scat searches and camera trap boxes. Results showed that stoat abundance in RBC project sites was 2.5 times higher than in pseudo-control sites. This demonstrates that regional, collaborative conservation efforts to enhance local micro-habitat heterogeneity promote stoat populations in intensively farmed landscapes, highlighting their valuable contribution to wider-scale biodiversity conservation. • Landscape scale biodiversity conservation projects boost stoat numbers in farmland • Stoats were 2.5x more abundant in regions with conservation initiative than without • Coordinated efforts at regional scale can improve wildlife in agricultural areas • Positive effect driven by expert-led, regional projects, not by number of measures