Community-mediated mechanisms to stabilize pollination of agricultural production highly dependent on shrinking honey bee populations under global change
Final Report Abstract
Crop pollination in general and almond pollination in particular is today a critical ecosystem service for agricultural production. Since honey bee colony losses are still unpredictable and the availability of honey bees for early flowering crops is uncertain, research understanding if wild bees can provide the pollination services and under which condition they are foraging is needed. Furthermore, understanding the role of biodiversity for pollination services help to understand if we can rely on single pollinator management and define the conditions when single pollinator management is a risky management practice. In this project we show that the proportion of semi-natural habitat surrounding almond orchards, but also any other pollinator-dependent crop, mainly drives pollinator diversity and flower-visitation frequency. Organic management in landscapes without semi-natural habitats will not offset the important role of semi-natural habitat as source habitat for bee pollinators. Also the currently available but mainly degraded semi-natural habitat strips in the California agricultural intensive landscapes do not provide quality habitat for wild bees; even so few wild bees persist in these non-agricultural strips. Almond trees receiving wild bee visits gets more equally pollinated as honey bees prefer the upper parts of the trees when it is not windy but wild bees and flies forage also on lower and inner parts of the trees. In high wind, honey bees do not forage but some wild bee species forage under high windy conditions ensuring pollination services under uncertain environmental conditions. Furthermore, the availability of wild bees forces the honey bees to switch more often between compatible almond varieties leading to higher pollination services. But until the end of the project, we missed finding the mechanism of this synergistic interactions found under real orchard conditions and in a cage experiment. Finally, this project shows interesting results for a promising new research direction as pollination was shown to affect the nutritional (mirocnutrient) status of the almond nuts. If this is similar for other crops, the quality of pollination services in especially developing countries maybe directly linked to human health. In conclusion, this project identified negative feedbacks of modern intensive agricultural landscapes to crop production that lost free pollination services of high biodiversity. Relying on single pollinator species management is therefore a risky strategy. Our results are of interest to almond and other fruit tree growers but the success of restoring land for pollinators in intensive agricultural landscapes like in California will not only depend on informing growers or politicians. Follow up projects with the goal to implement new management practices for “biodiversity habitat” in agricultural landscapes need to integrate the perspectives of all interest groups and find common definitions and protocols to restore and evaluate the restoration success. Klein, A.M.: Teamarbeit: Honigbienen können nur gemeinsam mit wildlebenden Insekten die Bestäubung von Kulturpflanzen sichern. Deutsches Bienenjournal 5 (2013):12-14
Publications
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2012. Wild pollination services to California almond rely on semi-natural habitat. Journal of Applied Ecology 49: 723-732
Klein, A.M., Brittain, C., Hendrix, S.D., Thorp, R., Williams, N., Kremen, C.
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2013. A global quantitative synthesis of local and landscape effects on native bee pollinators in agroecosystems. Ecology Letters 15: 584-599
Kennedy, C.M. et al. (including Klein, A.M., Brittain, C.)
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2013. Biodiversity buffers pollination from changes in environmental conditions. Global Change Biology 19: 540-547
Brittain, C., Kremen, C., Klein, A.M.
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2013. Biodiversity-friendly farming. In: Levin, S.A. (ed.) Encyclopedia of Biodiversity, 2nd Edition, Elsevier, New York, pp. 418-429
Fischer, J., Brittain, C., Klein, A.M.
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2013. Synergistic effects of non-Apis bees and honey bees for pollination service. Proceedings of the Royal Society: B Biological Sciences
Brittain, C., Williams, N., Kremen, C., Klein, A.M.
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2013. Wild pollinators enhance fruit set of crops regardless of honey-bee abundance. Science 339: 1608-1611
Garibaldi, L.A., Klein, A.M. et al.
