Direct and indirect effects of agricultural practices, landscape complexity and climate on insectivorous birds, pest abundance and damage in olive groves

Abstract

Pesticides used in agriculture to prevent yield and economic loss are a threat for the natural heritage worldwide. Finding win-win solutions for pest control management in sustainable and profitable agriculture is a current yet elusive challenge for human societies. The main alternative to reduce pest damage in a sustainable manner consists in fostering natural enemies through the extensification of agricultural practices or the promotion of heterogeneous landscapes. However, very few studies have analyzed the combined effects of these components on natural enemies and pests simultaneously.In this work, we fit meta-models (using Piecewise Structural Equation Models) aiming to understand the direct and indirect effects of agricultural management, landscape heterogeneity and climatic variables on insectivorous birds, pest abundance and crop damage. For this, we focus on olive groves, one of the most important woody agroecosystems worldwide, and its two main pest species.We found that management extensification and landscape heterogeneity benefited pest control and supported more insectivorous birds. Also, high temperatures diminished pest damage. Compared to landscape and temperature effects, abundance/richness of insectivorous birds were poor predictors of pest abundance and damage, suggesting that other natural enemies might be currently more important for pest control in olive groves. Lastly, we found a decoupled response of pest abundance and pest damage that may be attributed to insecticide use. This suggests that predation pressure by birds might predict better pest abundance than pest damage in our system.Current predation pressure by birds against pests in olive groves seems very low. Fostering extensive management and landscape heterogeneity increases the abundance of insectivorous birds in this system, potentially enhancing the pest control service.