Carabidae Diversity in Olive Orchards Under Conventional and Organic Management with Green Infrastructure

Research on Carabidae diversity in Greek olive-orchard agroecosystems is limited, although olive orchards can support diverse soil–fauna communities, while carabids may contribute to the biological control of olive-tree pests and serve as potential bioindicators of olive-orchard soil health. The present study aimed to investigate the diversity of ground beetles in olive orchards of the Messara Plain in Crete, Greece, with regard to their potential contribution to the biological control of olive pests. Carabidae beetles were collected during a continuous 24-month survey in 12 olive orchards located in two agroecological zones (AZs) (hilly and plain) and managed under two management contexts: six organic orchards implementing Green Infrastructure (GI) and six conventional orchards. Furthermore, a survey was conducted in three adjacent natural areas overgrown with phrygana. In addition, a literature and database review was conducted, listing all previously recorded species from the surrounding area. In total, 12 Carabidae species belonging to 12 genera were recorded in the olive orchards and adjacent natural areas, along with two additional genera that could not be identified to the species level. Carabidae activity-density was statistically significantly higher in plain orchards, and season also significantly affected Carabidae activity-density. In contrast, no detectable difference in activity-density was observed between organic management with GI and conventional management systems, although the relatively small number of orchards limits the statistical power of this comparison. According to the literature, seven species have previously been reported from the study area. Our study complements these historical records of Carabidae species in the area by contributing to the ongoing documentation of species occurrence and distribution. Agroecological zone strongly influenced Carabidae species composition, while Indicator-Species Analysis (ISA) identified three species that were closely associated with the plain agroecological zone. The findings highlight the importance of olive orchards as habitats supporting notable carabid richness. Overall, the study emphasizes the potential value of Carabidae as bioindicators of agroecosystem conditions and highlights the need for further investigation of their ecological functions and agroecological importance in olive-orchard agroecosystems.