Land consolidation impacts the abundance and richness of natural enemies but not pests in small-holder rice systems

Traditional small-holder agricultural landscapes in southern China are being consolidated to increase mechanisation levels in agriculture, but it is unclear how this influences rice arthropod communities in these landscapes. Here, based on a six-year study in 20 rice fields, we evaluated the impact of land consolidation on arthropod communities, crop damage, and rice yield. We also analysed how effects of land consolidation were moderated by the proportion of large semi-natural habitat patches and insecticide use. We found that, compared to consolidated fields, rice fields in traditional farmlands had a higher abundance and family richness of natural enemies, but a similar abundance of rice pests. Land consolidation did not significantly interact with the proportion of large semi-natural habitat patches or insecticide application, in terms of affecting arthropods. The proportion of semi-natural habitat reduced the negative effect of insecticide application on key rice pests, but no equivalent interaction occurred for natural enemies. Synthesis and applications: Land consolidation can have negative impacts on the abundance and richness of natural enemies, but not pests in small-holder rice systems, and these impacts are independent from insecticide application and proportion of semi-natural habitat in the landscape. We recommend the implementation of agri-environmental measures or re-establishing field margin vegetation during the consolidation process to mitigate these potential negative effects, although trade-off between enhancing crop yields and preserving rice arthropod biodiversity should be considered. We encourage future research to focus on the detailed assessment of the function of linear habitats for a better understanding of the impact of land consolidation.