Experimental addition of branch and stone piles increases reptile abundance in agricultural landscapes

Agricultural intensification has reduced farmland habitat heterogeneity, contributing to biodiversity decline. Small structural elements such as stone and branch piles are widely recommended to mitigate this loss, yet their effectiveness for promoting biodiversity in high-intensity farmland has not been tested experimentally. We evaluated the effects of adding small structures along agricultural field margins on reptile abundance across 14 regions of the Swiss Plateau. Using a replicated randomized block design, we applied two experimental treatments (branch and stone piles) and compared them with untreated control sites. Reptiles were surveyed repeatedly using two complementary methods and analysed within a hierarchical modelling framework that accounted for imperfect detection. Results showed that small structures substantially increased reptile abundance relative to controls. Branch piles produced strong, consistent positive effects across all focal species, with abundances ca. 4–13 times higher than in controls. Stone piles also showed positive effects, with estimated abundances approximately 2–6 times higher than in controls, although posterior support for positive effects was generally weaker and varied among species. The whole reptile assemblage benefitted from these structures, including the sand lizard Lacerta agilis , a species of particular conservation concern across Europe. Our findings provide robust experimental evidence that adding small structural elements enhances reptile abundance in otherwise intensively managed farmland. Given their low implementation costs, minimal space requirements and compatibility with existing farming practices, small structures represent a practical and scalable conservation measure for restoring fine-scale habitat heterogeneity in agricultural landscapes.