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The recent intensification of the arable landscape by modern agriculture has had negative effects on biodiversity. Organic farming has been introduced to mitigate negative effects, but is organic farming beneficial to biodiversity? In this review, we summarize recent research on the effects of organic farming on arable biodiversity of plants, arthropods, soil biota, birds, and mammals. The ecosystem services of pollination, biological control, seed predation, and decomposition are also included in this review. So far, organic farming seems to enhance the species richness and abundance of many common taxa, but its effects are often species specific and trait or context dependant. The landscape surrounding the focal field or farm also seems to be important. Landscape either enhances or reduces the positive effects of organic farming or acts via interactions where the surrounding landscape affects biodiversity or ecosystem services differently on organic and conventional farms. Finally, we discuss some of the potential mechanisms behind these results and how organic farming may develop in the future to increase its potential for sustaining biodiversity and associated ecosystem services. [ABSTRACT FROM AUTHOR]

Organic farming in Europe has been shown to enhance biodiversity locally, but potential interactions with the surrounding landscape and the potential effects on ecosystem services are less well known. In cereal fields on 153 farms in five European regions, we examined how the species richness and abundance of wild plants, ground beetles and breeding birds, and the biological control potential of the area, were affected by organic and conventional farming, and how these effects were modified by landscape complexity (percentage of arable crops within 1000 m of the study plots). Information on biodiversity was gathered from vegetation plots, pitfall traps and by bird territory mapping. The biological control potential was measured as the percentage of glued, live aphids removed from plastic labels exposed in cereal fields for 24 h. Predation on aphids was highest in organic fields in complex landscapes, and declined with increasing landscape homogeneity. The biological control potential in conventional fields was not affected by landscape complexity, and in homogenous landscapes it was higher in conventional fields than in organic fields, as indicated by an interaction between farming practice and landscape complexity. A simplification of the landscape, from 20% to 100% arable land, reduced plant species richness by about 16% and cover by 14% in organic fields, and 33% and 5·5% in conventional fields. For birds, landscape simplification reduced species richness and abundance by 34% and 32% in organic fields and by 45·5% and 39% in conventional fields. Ground beetles were more abundant in simple landscapes, but were unaffected by farming practice. Synthesis and applications. This Europe-wide study shows that organic farming enhanced the biodiversity of plants and birds in all landscapes, but only improved the potential for biological control in heterogeneous landscapes. These mixed results stress the importance of taking both local management and regional landscape complexity into consideration when developing future agri-environment schemes, and suggest that local-regional interactions may affect other ecosystem services and functions. This study also shows that it is not enough to design and monitor agri-environment schemes on the basis of biodiversity, but that ecosystem services should be considered too. [ABSTRACT FROM AUTHOR]

Numerous studies show that landscape simplification reduces abundance and diversity of natural enemies in agroecosystems, but its effect on natural pest control remains poorly quantified. Further, natural enemy impacts on pest populations have usually been estimated for a limited number of taxa and have not considered interactions among predator species. In a quantitative synthesis with data collected from several cropping systems in Europe and North America, we analyzed how the level and within-field spatial stability of natural pest control services was related to the simplification of the surrounding landscape. All studies used aphids as a model species and exclusion cages to measure aphid pest control. Landscape simplification was quantified by the proportion of cultivated land within a 1 km radius around each plot. We found a consistent negative effect of landscape simplification on the level of natural pest control, despite interactions among enemies. Average level of pest control was 46% lower in homogeneous landscapes dominated by cultivated land, as compared with more complex landscapes. Landscape simplification did not affect the amount of positive or negative interactions among ground-dwelling and vegetation-dwelling predators, or the within-field stability of pest control. Our synthesis demonstrates that agricultural intensification through landscape simplification has negative effects on the level of natural pest control with important implications for management to maintain and enhance ecosystem services in agricultural landscapes. Specifically, preserving and restoring semi-natural habitats emerges as a fundamental first step to maintain and enhance pest control services provided by predatory arthropods to agriculture. [ABSTRACT FROM AUTHOR]