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Ecosystem services in agricultural landscapes: the case of Flemish apple farming

Boek - Dissertatie

Since the second world war, agriculture in the EU has become increasingly intensive through the introduction of high-yielding crop varieties, advanced farming techniques, and the replacement of biological functions and services with high inputs of synthetic fertilizers and pesticides. While these practices have boosted agricultural production, food security, food quality, and economic development, they have also resulted in severe environmental problems. Together with further agricultural expansions at the detriment of natural habitats, agricultural intensification has caused severe degradation of biodiversity and biodiversity-based ecosystem services (ES). To prevent further environmental degradation and ensure long-term food security, organic farming is increasingly being promoted as a more environmentally-friendly alternative to conventional farming, as it abandons the use of synthetic inputs and stimulates natural ecosystem functions and services to grow and protect crops. However, despite the steady growth of the organic sector, the actual performance of organic farming in sustaining and enhancing biodiversity and the provisioning of multiple ecosystem services remains poorly understood. This is especially the case for perennial crops, where studies are relatively scarce and often report inconsistent results. Additionally, most studies to date also lack a comparison with a semi-natural benchmark, while this can provide valuable insights into the extent to which biodiversity and biodiversity-based services are affected by different types of agricultural management. Furthermore, also the lower productivity of organic farming relative to conventional farming may raise questions about its sustainability when applied across large areas. Due to lower yields, organic systems indeed require more land per unit of food produced, meaning that for similar production levels, organic systems might have a similar or even greater environmental impact than conventional systems. In summary, more insights are needed into the ecological, agronomical, and economic performance of organic farming, to better evaluate its effectiveness in stimulating environmental, agricultural, and socio-economic sustainability. In this study, we therefore quantified a set of indicators for ecological, agronomical, and economic performance in organic and integrated pest management (IPM) apple orchards, and assessed how these were affected by both local management and the landscape context. Additionally, we compared the ecological performance of both organic and IPM orchards with a semi-natural reference system to better evaluate their potential for biodiversity conservation and maintenance of ecosystem service provisioning. First, we compared physical, chemical, and biological soil health indicators among organic orchards, IPM orchards, and semi-natural grasslands. No significant differences in soil health between the organic and IPM orchards were found, and neither farming systems showed any evidence of impaired soil health compared to the semi-natural reference, except for higher litter decomposition rates in both orchard types. This suggests that both organic and IPM apple orchards can be managed sustainably in terms of soil health. Nonetheless, the presence of spatial variability in soil health between drive rows and crop rows within orchards suggests that soil management can still be improved, especially in the crop rows of IPM orchards. Next, we assessed the effects of organic management and the landscape context on biological pest control and pollination services. Natural enemies were more abundant in organic orchards than in IPM orchards, which had a small beneficial effect on biological control services, but overall did not affect pest infestation levels. Moreover, pest infestation levels were positively affected by organic management and the presence of semi-natural habitat in the surrounding landscape. These findings indicate that factors that enhance natural enemies can be even more beneficial to pest species, highlighting the importance of balancing ecosystem services and disservices when designing environmentally-friendly agricultural landscapes. Relative to the semi-natural reference, both organic and IPM orchards showed degraded predator communities and a lower potential for biological pest control. For pollinator communities, few differences were found between organic and IPM orchards, and these did not affect differences in pollination services or yield levels. Instead, yield levels were directly and negatively affected by organic orchard management. Pollinator communities in both organic and IPM orchards benefited from orchard edges, high landscape diversity, and the presence of semi-natural habitat, but were overall less abundant and diverse than those in the semi-natural benchmark. Furthermore, the results obtained for soil-based services, biological pest control, and pollination were combined with measures of biodiversity, yield, and farmer income to quantify overall agroecosystem multifunctionality and to identify possible synergies and trade-offs among services. Overall multifunctionality measures did not differ between organic and IPM orchards, and a clear trade-off between biodiversity and yield was found in both systems. In conclusion, the relatively limited benefits of organic farming practices in terms of biodiversity conservation and ES provisioning, in combination with the high yield gap relative to the IPM system, indicate the need to look further than the organic/conventional dichotomy to improve orchard sustainability. Maintaining and increasing orchard edges, semi-natural habitats, and landscape complexity seems to be a more effective biodiversity conservation strategy that can also provide the required ES. The presence of a clear trade-off between biodiversity and yield, even across management systems, and the much higher biodiversity in our semi-natural benchmark further support this conclusion. Therefore, we argue that the focus in apple orchards should be on maintaining or improving functional agrobiodiversity to safeguard ecosystem service provisioning, and that more attention should be given to the preservation of semi-natural habitats for their role in regional biodiversity conservation. Finally, our study supports the view that improving the environmental, agricultural, and socio-economic sustainability of farming requires close collaboration between different stakeholders at the landscape level and adequate policy support at regional, national, and international levels.
Jaar van publicatie:2023