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Functional Agrobiodiversity

Subject Area Ecology of Land Use
Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
Term from 2021 to 2023
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 493487387
 

Final Report Abstract

Agricultural intensification and urbanization are major drivers of biodiversity loss and impair ecosystem services that are vital for agriculture. This Heisenberg project focussed on ecological intensification measures to replace external inputs through the enhancement of functional agrobiodiversity and ecosystem services. Grain legumes offer floral resources and improve nutrient availability. We found that faba bean (Vicia faba) cultivation enhanced landscape-wide bumblebee densities, while other wild bee species do not benefit. Legume-cereal intercrops had higher yields than sole crops despite reduced flower abundance that did not reduce flower visitation by bumblebees. Mass-flowering crops, such oilseed rape (Brassica napus), act as environmental filter through past and present cultivation pattern and modified the functional composition of bee communities. Based on pollen metabarcoding and waggle dance decoding, we found that bees adapt their foraging decisions to the landscape-wide availability of resources with implications for the provisioning of pollination services. The smart design of macadamia orchards (Macadamia integrifolia) through the perpendicular arrangement of tree rows to semi-natural habitats improved quantity and quality of yields. However, effective pollinator management needs to consider that many wild bee species rely on diverse floral resources and nesting-sites. In a tropical megacity, we investigated bird and pollinator communities and pollination services in urban agricultural systems. Along the urbanization gradient, bird communities experienced biotic homogenization through losses of insectivorous bird species, which can impair biological pest control. Functional responses to urbanization were also trait-specific in bee communities with, however, more positive than negative effects as several functional groups benefited from urbanization, including dietary specialist and ground-nesting bee species. Mango (Mangifera indica) is an important crop, which is often cultivated in tropical cities. We found that urbanization and insecticide applications interact and that higher amounts of insecticides reduced mango yields by almost 30% in rural orchards. Urbanization amplified the seasonal dynamics of plant-pollinators networks by greater turnover of native plant species. Urban agriculture can contribute to the conservation of biodiversity and ecosystem services in tropical cities, if farm management adopts ecological intensification through crop diversification and the preservation of native plant species in semi-natural habitats. The transformation of rainforests improves the livelihood of many smallholder farmers but also causes negative environmental impacts. Not only biodiversity but also food web structure and energy fluxes change across rainforest transformation systems. Moreover, we found that careful intensification of smallholder farms can reduce yield gaps, while reduced management intensity in conventional plantation will not result in yield losses. Scientific outcomes of this Heisenberg project indicate multiple pathways of local and landscape-wide measures for ecological intensification across tropical and temperate cropping systems. Combinations of novel cropping practices and landscape-scale measures that improve landscape heterogeneity are the most promising strategies to sustain biodiversity, ecosystem functionality and agricultural productivity.

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