Bees increase seed set of wild plants while the proportion of arable land has a variable effect on pollination in European agricultural landscapes

Background and aims: Agricultural intensification and loss of farmland heterogeneity have contributed to population declines of wild bees and other pollinators, which may have caused subsequent declines in insect-pollinated wild plants. Material and methods: Using data from 37 studies on 22 pollinator-dependent wild plant species across Europe, we investigated whether flower visitation and seed set of insect-pollinated plants decline with an increasing proportion of arable land within 1 km. Key results: Seed set increased with increasing flower visitation by bees, most of which were wild bees, but not with increasing flower visitation by other insects. Increasing proportion of arable land had a strongly variable effect on seed set and flower visitation by bees across studies. Conclusion:Factors such as landscape configuration, local habitat quality, and temporally changing resource availability (e.g. due to mass-flowering crops or honey bee hives) could have modified the effect of arable land on pollination. While our results highlight that the persistence of wild bees is crucial to maintain plant diversity, we also show that pollen limitation due to declining bee populations in homogenized agricultural landscapes is not a universal driver causing parallel losses of bees and insect-pollinated plants.
The original idea was conceived aspart of the project ‘STEP - Status and trends of Europeanpollinators’ funded by the European Union in the 7thFramework Programme (grant 244090), which fundedRB, ISD, HGS, SP, MR, LH, JME, and KS. JE and PCwere funded by MULTAGRI/FORMAS. MA was fundedby the EU FP5 project ‘Evaluating current European agri-environment schemes to quantify and improve natureconservation efforts in agricultural landscapes’ (EASY;QLRT-2001-01495) and the Swiss Federal Office for Scienceand Technology (01·0524-2). AJ and EÖ were funded byFORMAS. TTe and VS were supported by institutionalresearch funding IUT (IUT20-33) of the Estonian Ministryof Education and Research, and TTe also received funding(grant no. 42900/1312/3166) from the Internal Grant Agencyof the Faculty of Environmental Sciences, Czech Universityof Life Sciences Prague. IB was funded by MC-CIG BeeFunproject: PCIG14-GA-2013-631653 and thanks the DoñanaNP staff members for granting access to the Park and CurroMolina for conducting the field work. JS, EFP, and SM werefunded by DAFM and IRC. LH was funded by a grant fromFormas to HGS and by a mobility grant from Formas (2018-01466). ALH was funded by the FarmLand project supportedby the German Ministry of Research and Education (FKZ:01LC1104A). AKH was supported by the NKFIH project 348Pl. Ecol. Evol.154 (3), 2021(FK123813) and was a Bolyai Fellow of MTA. PB wassupported by the NKFIH (KKP 133839).