Experimental evidence that even minor livestock trampling has severe effects on land snail communities in forest remnants.
Land-use intensification is increasing dramatically in production systems world-wide. Livestock production is an important component of production land use, and increases in livestock densities have had a wide range of negative consequences. The off-site effects of livestock grazing and trampling on native vegetation adjacent to pastoral land have received less attention than on-farm effects. Moreover, where significant ecological effects of livestock spillover have been identified, the mechanistic determinants of these effects have not typically been investigated. Here, we tested the mechanistic drivers of livestock trampling effects on land snail communities in forest remnants using simulated trampling under field conditions. We used a factorial combination of leaf-litter manipulation and trampling treatments to partition different causal drivers of livestock impacts on land snail communities and related them to five environmental variables that are altered by livestock. We show that even very low frequency trampling caused severe changes to land snail communities. Land snail density, even under the lowest trampling frequency, declined by an average of 42 individuals m-2 and land snail species richness decreased by an average of 10 species per plot compared with control plots. The underlying drivers of changes in land snail communities varied, but were primarily linked to leaf-litter mass, rather than soil compaction. Synthesis and applications. Overall, these results suggest that even minimal disturbance by livestock has large effects on land snail communities, but the underlying drivers of these effects require further investigation in longer duration and more intensive studies. Our results provide strong support for livestock exclusion as an important management tool for native forest remnants embedded within production landscapes.