BackgroundIntensively cultivated agricultural landscapes often suffer from substantial pollinator losses, which may be leading to decreasing pollination services for crops and wild flowering plants. Conservation measures that are easy to implement and accepted by farmers are needed to halt a further loss of pollinators in large areas under intensive agricultural management. Here we report the results of a replicated long-term study involving networks of mostly perennial flower strips covering 10% of a conventionally managed agricultural landscape in southwestern Germany.ResultsWe demonstrate the considerable success of these measures for wild bee and butterfly species richness over an observation period of 5 years. Overall species richness of bees and butterflies but also the numbers of specialist bee species clearly increased in the ecological enhancement areas as compared to the control areas without ecological enhancement measures. A three to five-fold increase in species richness was found after more than 2 years of enhancement of the areas with flower strips. Oligolectic bee species increased significantly only after the third year.ConclusionsIn our long-term field experiment we used a large variety of seed mixtures and temporal variation in seeding time, ensured continuity of the flower-strips by using perennial seed mixtures and distributed the measures over c. 10% of the landscape. This led to an increase in pollinator abundance, suggesting that these measures may be instrumental for the successful support of pollinators. These measures may ensure the availability of a network of diverse habitats and foraging resources for pollinators throughout the year, as well as nesting sites for many species. The measures are applied in-field and are suitable for application in areas under intensive agriculture. We propose that flower strip networks should be implemented much more in the upcoming CAP (common agricultural policy) reform in the European Union and promoted more by advisory services for farmers.Electronic supplementary materialThe online version of this article (10.1186/s12898-018-0210-z) contains supplementary material, which is available to authorized users.

Abstract. 1. Sympatric flower visitor species often partition nectar and pollen and thus affect each other's foraging pattern. Consequently, their pollination service may also be influenced by the presence of other flower visiting species. Ants are solely interested in nectar and frequent flower visitors of some plant species but usually provide no pollination service. Obligate flower visitors such as bees depend on both nectar and pollen and are often more effective pollinators.2. In Hawaii, we studied the complex interactions between flowers of the endemic tree Metrosideros polymorpha (Myrtaceae) and both, endemic and introduced flowervisiting insects. The former main-pollinators of M. polymorpha were birds, which, however, became rare. We evaluated the pollinator effectiveness of endemic and invasive bees and whether it is affected by the type of resource collected and the presence of ants on flowers.3. Ants were dominant nectar-consumers that mostly depleted the nectar of visited inflorescences. Accordingly, the visitation frequency, duration, and consequently the pollinator effectiveness of nectar-foraging honeybees (Apis mellifera) strongly decreased on ant-visited flowers, whereas pollen-collecting bees remained largely unaffected by ants. Overall, endemic bees (Hylaeus spp.) were ineffective pollinators.4. The average net effect of ants on pollination of M. polymorpha was neutral, corresponding to a similar fruit set of ant-visited and ant-free inflorescences.5. Our results suggest that invasive social hymenopterans that often have negative impacts on the Hawaiian flora and fauna may occasionally provide neutral (ants) or even beneficial net effects (honeybees), especially in the absence of native birds.

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Farmland biodiversity has dramatically declined in European agricultural landscapes over the past century. The key driver of this decline is the intensification of farming practices. In response, various policies have been developed to protect and promote farmland biodiversity, including so-called greening measures under the Common Agricultural Policy(CAP). However, there is currently very little systematically collected data on the ecological quality of European farmland. Therefore, we developed a survey method to provide repeatable and comparable data. This method comprises the mapping of land use and ecological quality of parcels in sample plots of 500 m x 500 m, vegetation transects on up to four predefined parcels in each sample plot and a photo documentation of the transects and the whole plot. Using this LISA method (Landscape Infrastructure and Sustainable Agriculture), we investigated about 25plots in each of 35 regions in 2014 and 13 regions in 2016, altogether in 10 EU countries. The methodology provides a time- and cost-efficient possibility to collect standardised data on the ecological quality of farmland habitats. We show that biodiversity in arable fields is at an extremely low level. The survey methodology proved to be applicable in all parts of Europe and thus being applied widely it could deliver a representative view on the ecological situation of all agricultural landscapes in Europe.

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