Historical nectar assessment reveals the fall and rise of floral resources in Britain

Abstract

SummaryThere is considerable concern over declines in insect pollinator communities and potential impacts on the pollination of crops and wildflowers [1][2][3][4] . Among the multiple pressures facing pollinators [2][3][4] , decreasing floral resources due to habitat loss and degradation has been suggested as a key contributing factor 2-8 . However, a lack of quantitative data has hampered testing for historical changes in floral resources. Here we show that overall floral rewards can be estimated at a national scale by combining vegetation surveys and direct nectar measurements. We find evidence for substantial losses in nectar resources in England and Wales between the 1930s and 1970s; however, total nectar provision in Great Britain as a whole had stabilised by 1978, and increased from 1998 to 2007. These findings concur with trends in pollinator diversity, which declined in the mid-20th century 9 but stabilised more recently 10 . The diversity of nectar sources declined from 1978 to 1990 but stabilised thereafter at low levels, with four plant species accounting for over 50% of national nectar provision in 2007. Calcareous grassland, broadleaved woodland and neutral grassland are the habitats that produce the greatest amount of nectar per unit area from the most diverse sources, whereas arable land is the poorest in both respects. While agrienvironment schemes add resources to arable landscapes, their national contribution is low. Due to

Flower preferences and pollen transport networks for cavity‐nesting solitary bees: Implications for the design of agri‐environment schemes

“…It is vital that bees and other pollinating insects have access to floral foraging resources throughout the adult flight season to meet their energetic requirements and maximize reproductive output (Müller et al., 2006; Vaudo, Tooker, Grozinger, & Patch, 2015). However, wildflower foraging resources have declined across much of the British countryside over the last century, a trend which is thought to have been a major contributor to long‐term declines in bee populations (Baude et al., 2016; Brown & Paxton, 2009; Goulson, Lye, & Darvill, 2008; Vanbergen, 2013). …”

Oilseed rape (Brassica napus) as a resource for farmland insect pollinators: quantifying floral traits in conventional varieties and breeding systems

“…However, pollination services in farmed landscapes are threatened, and global declines in insect pollinator abundance and richness (Biesmeijer et al ., 2006; Potts et al ., 2010; Cameron et al ., 2011; Carvalheiro et al ., 2013) have been attributed, in part, to limited quality and availability of food resource, particularly as a result of land use change associated with agricultural intensification (Klein et al ., 2007; Potts et al ., 2010; Goulson et al ., 2015). Recent evidence has revealed the relative paucity of nectar sources in arable farmland compared with seminatural habitats (Baude et al ., 2016) and in such landscapes where alternative food sources are limited, mass‐flowering crops, such as OSR, to create large spatio‐temporal pulses of nectar and pollen that are exploited by wild and managed insect pollinators (Stanley & Stout, 2013; Gill & O'Neal, 2015; Requier et al ., 2015). Cultivation of OSR has been shown to enhance within‐season pollinator abundance (Westphal et al ., 2003; Williams et al ., 2012) and more significantly, between‐year populations (Jauker et al ., 2012; Holzschuh et al ., 2013; Riedinger et al ., 2015).…”

Long-term vegetation monitoring in Great Britain – the Countryside Survey 1978–2007 and beyond

“…Depending on the type of analyses in question, data users may wish to account for spatial auto-correlation, as in Baude et al (2016). However, in the majority of cases this is not an issue, as described by Betts et al (2009), and as shown by in model checks in, for example, Henrys et al (2015b).…”

“…While research into the causes and consequences of eutrophication was a response to clear policy interest, analysis of CS vegetation data has also contributed evidence in response to concerns over the causes and consequences of loss of pollinators in north-west Europe and Britain Carvell et al, 2006;Baude et al, 2016). Habitat specific studies, such as those relating to woodlands (for example Petit et al, 2004;Kimberley et al, 2013Kimberley et al, , 2016 and hedgerows, McCollin et al, 2000;Garbutt and Sparks, 2002;Critchley et al, 2013) have been facilitated through the use of CS data.…”