Pollinator conservation in urban and agricultural environments: comparison of management practices

• INT82 • Wild bee conservation in the city and countryside > T. Teja TSCHARNTKE
Content : Teja TSCHARNTKE, professor, Agroecology, University of Göttingen, Germany Email: ttschar@gwdg.de

The intensification and expansion of agriculture as well as the increase of urbanisation are major threats to biodiversity, endangering wild bee communities and their pollination services. Biodiversity management in both land-use types needs to consider trade-offs, somewhere in between land-sharing and land-sparing strategies. Regarding land-sharing, urban sprawl is similar to wildlife-friendly farming. In contrast, densification of house building and agricultural intensification belong to a land sparing strategy, which keeps the area devoted to buildings or cropland at a minimum in order to protect as much nature as possible for conservation. In this presentation, I discuss the significance of maintaining or restoring wild bee communities and their pollination services. Further, the components of cities enhancing wild bees as well as features of urban wild bee communities are discussed. In the countryside, a range of management practices for wild bee conservation is in place. I emphasize the benefits of green space in cities and question the widespread assumption that organic farming is the overarching solution for conservation in agricultural landscapes. Reducing field size considerably (to one or few ha), greatly diversifying cropland and keeping a minimum of semi-natural habitat (>20%) are far more effective strategies to restore biodiversity in agricultural landscapes, but not covered by organic certification. In conclusion, a good life in cities and in the countryside, providing social-ecological services, requires a minimum of near-natural habitat for human recreation and wildlife experience. This can be managed in a biodiversity-friendly way, thereby protecting rich wild bee communities. • INT83 • Ecological and social drivers of wild bee conservation in urban gardens > M. Monika EGERER
Content : Monika EGERER, professor, Technical University of Munich TUM School of Life Sciences Hans Carl-von-Carlowitz-Platz Freising, Germany
Email: monika.egerer@tum.de

Cities are a new frontier to understand how land use change drives changes in pollinator biodiversity. Local flower diversity, vegetation structural complexity, nesting resource availability, landscape composition and fragmentation are some potential ecological drivers of pollinator diversity and conservation. Yet, as human dominated landscapes, the conservation of pollinators also requires a social understanding of management decisions to catalyze restoration action. Urban gardens represent a common, novel urban habitat that can provide diverse flower and nesting resources to potentially promote pollinators. In turn, these systems are designed and managed by residents of diverse values, attitudes and motivations – all of which can influence habitat management decisions. Thus, urban gardens are ideal systems to investigate both ecological and social drivers of pollinator conservation. Here I use research in urban gardens in Berlin and Munich, Germany, to discuss important ecological and social drivers of wild bee conservation. I highlight how land use, plant management and specific proxies of ‘wildness’ in urban gardens drive wild bee diversity. But I also show how people’s values, attitudes and emotions towards wild bees and other pollinators are critical factors that underly such management decisions, and could be better harnessed to enhance wild pollinator conservation action. Thus, urban ecological research and practice must acknowledge interactions among ecological and social drivers, ultimately seeking to foster synergies to promote wild bees and other pollinators in our city landscapes. • INT84 • Contribution of floral resources provided by crops, weeds and wild plants in supporting wild pollinating insects in agricultural landscapes > S. Stéphanie AVIRON
Content : Stéphanie AVIRON, researcher, UMR Biodiversité Agroécologie et Paysage, INRAE, Agrocampus Ouest-ESA, Rennes, France
Email: stephanie.aviron@inrae.fr
S. Aviron1,3, T. Berry1,3, E. Jeavons1,3, C. Le Lann2,3, D. Leroy1,3, J. van Baaren2,3, A. Alignier1,3
1UMR 0980 BAGAP, INRAE-L’institut Agro Rennes-Angers-ESA, 64 rue de Saint Brieuc, 35042 Rennes Cedex, France
2UMR 6553 ECOBIO, CNRS-Université de Rennes 1, 263 avenue du Général Leclerc 35042 Rennes Cedex, France
3 LTER « Zone Atelier Armorique »

Vegetation diversification is considered a promising strategy to promote biodiversity, improve the functioning of agro-ecosystems without compromising crop yields in various farming systems. It can be set up at different spatial scales – field, field border, landscape - and targets both crop and non-crop vegetation. By enhancing flowering resources, such strategies might be suitable management options to promote pollinating insects in agricultural landscapes. The goals of the present study were i) to disentangle the effects of flowering resources provided by crop (leguminous plants in fields) and non-crop (weeds in fields, wild plants in hedgerows) vegetation diversity on flower-visiting insect abundances in crop fields and field borders, and ii) to assess whether these relationships are mitigated by the availability and diversity of crop and non-crop vegetation at the landscape scale. Surveys of flower visitors (including bumblebees, solitary bees, hoverflies, coleopteran, and butterflies) were carried out in 30 pairs of monocrops (cereals) and intercrops (cereal-legume) and adjacent hedgerows, along a gradient of landscape heterogeneity, in the Zone Atelier Armorique, France. Our results show that crop diversification though cereal-legume intercropping did not result in higher abundance of flower visiting insects in crop fields. By contrast, insect abundance was more driven by the amount and/or diversity of non-crop floral resources, i.e. flowering weeds in crop fields and flowering wild plants in hedgerows. Our results on interaction networks highlighted complex and specific plant-insect interactions in relationships with floral preferences of insects. The availability of crop and non-crop flowering resources at the landscape scale was even more important than local resource availability for some pollinators, indicating that it could mitigate insect responses to local vegetation diversification. Our study suggest that agri-environment schemes should promote a wide diversity of non-crop flowering resources, through the retention of existing semi-natural elements as well as adaptative weed management strategies. • INT85 • Understanding and managing the functional floral diversity of agrosystems and urban environments to conserve pollinating insects > A. Alice MICHELOT-ANTALIK
Content : Alice MICHELOT-ANTALIK, assistant professor, Laboratoire Agronomie et Environnement, Université de Lorraine, INRAE, Nancy, France
Email: alice.michelot@univ-lorraine.fr

Pollinator decline has been observed for different taxonomic groups for several decades and leads us to rethink the management practices. To maintain pollinator biodiversity in agricultural and urban environments, it is necessary to promote attractive and nutritive floral communities throughout the season and habitat connectivity. This requires knowledge on the relationships between floral trait diversity and abundance or diversity of pollinators and integration of a functional approach in floral community management. In agricultural landscape, I present a recent French study that highlights the links between floral functional diversity and pollinator diversity in different grassland habitats: marsh (Cotentin), mountain (Auvergne), mesophilic (Lorraine) and calcareous (Picardie). We measured floral height, floral area, nectar tube depth, nectar quantity and pollen quantity on 36 grassland plots. Our results show significant effects of different floral traits on pollinator visitation frequency in all grassland habitats. In urban environment, I highlight the links between management of floral resources and pollinator visits through experiments on grasslands and ornamental plants in green spaces of Nancy (France). Finally, I demonstrate that the management of floral communities in agricultural and urban environments must be based on a functional approach in interaction with the managers directly involved. • INT86 • How does urbanization impact on wild bees taxonomic and functional diversity? a large-scale study on three European countries > A. Arthur Fauviau FAUVIAU
Content : Arthur FAUVIAU, PhD student, Institut d’Ecologie et des Sciences de l’Environnement de Paris, Sorbonne-Université, Université de Paris, Paris, France
Email: arthur.fauviau@sorbonne-universite.fr

The expansion of urban habitats and associated land-use changes is one of the main drivers of the current decline of pollinating insects. However, effects of urbanization on pollinator communities are still unclear, as shown by contrasting reports on their species and functional diversities in urban habitats. Therefore, assessing how the management practices of these habitats impact on pollinating insect communities becomes increasingly important. Indeed, if recent studies emphasize on abundant and diverse pollinator communities in cities, they also point out the need to better manage urban areas to allow pollinators to persist. In the present study, we use a large dataset, encompassing pollinating insects surveys carried out in 20 cities of three West European countries (France, Belgium and Switzerland). Our objective is to link pollinator taxonomic and functional diversity to urban green spaces characteristics. To do so, we will analyze species richness in relation with the quantity of urban green spaces, their management practices and their connectivity in each city. We will also test if functional diversities of pollinator assemblages are related to these urban characteristics. As all cities do not equally affect pollinating insect communities, the results presented here will give important insights on the urban factors responsible for these differences. • INT87 • Wild bees benefit from low urbanization levels and suffer from pesticides in a tropical megacity > A. Arne WENZEL
Content : Arne WENZEL, Functional Agrobiodiversity Georg-August-University Grisebachstr. 637077 Goettingen, Germany “Wild bees benefit from low urbanization levels and suffer from pesticides in a tropical megacity”
awenzel@gwdg.de

Arne Wenzel1, Ingo Grass2, Nils Nölke3, Arati Pannure4, Teja Tscharntke5,6

1Functional Agrobiodiversity, University of Goettingen, 37077, Göttingen, Germany
2Institute of Agricultural Sciences in the Tropics, Department of Ecology of Tropical Agricultural Systems, University of Hohenheim, 70599 Stuttgart, Germany
3Forest Inventory and Remote Sensing, Faculty of Forest Sciences and Forest Ecology, University of Goettignen, 37077 Göttingen, Germany
4College of Agriculture and Sericulture, University of Agricultural Sciences, Bangalore(UASB), Chintamani, 563 125, India
5Centre of Biodiversity and Sustainable Land Use (CBL) University of Goettingen, Göttingen, Germany
6Agroecology, University of Goettingen, 37077, Göttingen, Germany

How urbanization affects crop pollination has scarcely been studied, especially in the tropics. We studied richness and abundance of wild bees and their pollination services to 30 small-scale fields of Lablab purpureus, a globally wide-spread grain legume, in the Indian megacity Bangalore. Farms were selected along a gradient of urbanization, measured as percentage of impervious surface (grey area) at the landscape scale, ranging from 0% to 30%. We found that the abundance of lablab-visiting wild bees increased with increasing grey proportions and that, in particular, ground-nesting, large-bodied and carpenter bees benefitted. The higher availability of forage and open soils in low-density urban areas appeared to enhance bee populations in Bangalore. When pollinating insects were experimentally excluded, lablab plants produced 36% less and 31% lighter fruits. Yet, we did not detect any changes of pollination outcomes along the urbanization gradient, as lablab seem to receive stable pollination services. Finally, we found that the local bee richness was negatively affected by the number of on-field pesticide applications, resulting in 35% fewer species after 3 application rounds. In summary, we conclude that low-density urbanization can be beneficial for wild bees in lablab farms, but intensive pesticide use could counteract this positive effect. Large and ground-nesting farmland bees benefited most from urbanization, but more studies on different crops in tropical cities are urgently needed. • INT88 • The misplaced management of bees in urban environments > B. Benoît GESLIN
Content : Benoît Geslin1, Lise Ropars2,3, Marie Zakardjian1 & Floriane Flacher1,4
1 Aix Marseille Univ, Avignon Université, CNRS, IRD, IMBE, Marseille, France.
2 ThéMA, UMR 6049 CNRS –Bourgogne Franche-Comté University, 32 Rue Mégevand, 25030, Besançon Cedex, France.
3 Biogéosciences, UMR 6282 CNRS –Bourgogne Franche-Comté University, 6 Boulevard Gabriel, 21000, Dijon, France
4 Independent Researcher, 2b rue de la Motte Picquet 35000 Rennes

To mitigate the negative impacts of anthropogenic activities on biodiversity, citizens and stakeholders are prone to modify their environment and manage biodiversity. Even if originally well-intentioned, some of these actions could have direct or indirect negative effects on biodiversity when ecology is not accounted for. The management of bees is a good example of misguided conservation. For the past few years, several practices originally designed to help bees have increased such as the installation of beehives in cities, the building of bee hotels and the trade of solitary bees. However, these actions could be counterproductive for biodiversity, doing more harm than good. In France, for several years, we have studied the impact of the management of bees on wild bee communities and plant-pollinator networks. We have shown that the density of hives, in urban and natural contexts, could negatively affect the foraging activity of wild bees. In particular, we showed that large bees suffer from exploitative competition for floral resources by honeybees. We also showed that bee hotels, in an urban context, are keener to host exotic bees compared to native ones, with potential negative implications for the latter. Finally, we studied the emerging practices of the bee cocoons trade and pointed out the risk that it may pose for native environments. We conclude our presentation by providing tailored solutions to help the bees and prioritize efficient conservation measures which consider more broadly the complexity of ecosystems.