Flower strip networks offer promising long term effects on pollinator species richness in intensively cultivated agricultural areas

Abstract

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.

Agri‐environment schemes enhance pollinator richness and abundance but bumblebee reproduction depends on field size

“…Abundances of all considered groups (hoverfly, solitary bee and bumblebee) and bee species richness reached their peaks in fields with flower strips. Therefore, our results back up evidence of pollinator enhancement from flower strips already found in literature (Blaauw & Isaacs, 2014; Buhk et al., 2018; Jönsson et al., 2015; Scheper et al., 2013). This response is likely due to additional nesting sites and rewarding food resources, such as Cirsium arvense or Phacelia tanacetifolia (Figure ; Ouvrard & Jacquemart, 2018).…”

Multiple methods of assessing nectar foraging conditions indicate peak foraging difficulty in late season

“…Practical steps taken to address the lack of forage range from encouraging the growing of bee-attractive ornamental garden flowers (Garbuzov et al, 2017) to government-managed agrienvironment schemes that subsidise farmers to help bees and wildlife, such as by planting buffer strips containing flowers (Batáry et al, 2015;Buhk et al, 2018). There is concern, however, that the existing schemes provide limited benefits, particularly to the less common solitary bee species (Wood et al, 2015(Wood et al, , 2017.…”

One-year-old flower strips already support a quarter of a city’s bee species

“…Monitoring and experiments have shown that such strips enhance the local plant and insect diversity in agricultural landscapes (e.g. Scheper et al 2015, Jönsson et al 2015, Buhk et al 2018, Dicks et al 2017 review 80 studies of flower strips).…”