Extinctions of aculeate pollinators in Britain and the role of large-scale agricultural changes

Abstract

but have declined in species richness, geographical range and abundance (2-5). Previous studies have assessed the roles played by habitat destruction and loss of flower resources (4,5), and pesticides (6) over relatively modest time scales and geographical ranges.Analyses of regions are rare (7-10) and our understanding of the effects of humanmediated actions over longer periods is limited. Here we assess the bee and flowervisiting wasp species that have gone extinct in Britain, using 494,117 records held by the Bees, Wasps and Ants Recording Society (BWARS), probably the most detailed available for a single country. We define extinct species as those that have not been recorded for at least 20 years following their last observation, despite extensive efforts by members of BWARS and other naturalists.Twenty-three bee and flower-visiting wasp species have become extinct in Britain (Table 1), including formerly widespread species. We exclude single early records that cannot be verified as representing stable breeding populations, but include one species which has recolonized Britain after an absence of six decades (see Supplementary Materials).Since the mid 19 th century the pattern of British bee and wasp extinctions has been characterized by intervals of relative stability, in which few species were lost, interspersed with times when over three species per decade went extinct ( Figure 1, Table 2). These data indicate a period of relatively sustained extinctions from the late 1920s to the late 1950s, with other isolated extinction peaks before and after this time. These features are confirmed in Figure 2, where the average gradient indicates the relative extinction rate over a period, and the period of sustained extinctions is evident as the phase of maximum gradient during the mid 20 th century.The varying rates of extinctions were quantified by applying breakpoint analysis to the cumulative record. In this analysis, a piecewise linear model is fitted to data to reveal periods of approximately constant extinction rate, separated by breakpoints where the rate changes. The analysis was iterated for up to 10 breakpoints and the Akaike Information Criterion (AIC), confirmed by coefficient of determination (multiple-R 2 ), was used to establish the best model (see Supplementary Materials). For these data, changes in AIC and muliple-R 2 level off for two models having four breakpoints (Table S2). These are very similar, sharing the latter three breakpoints, and revealing effectively identical periods of approximately uniform extinction rate for the majority of the 20 th century (Table 2).Both models must be interpreted with caution as the data for 'year last recorded' may not equate to 'year last living'. Declines in populations due to habitat changes may mean a species went unrecorded for some years prior to the actual extinction. The robustness of the breakpoints to this potential ambiguity of the probability of the 'year last living' has been assessed and, whilst there is some sensitivity in the timing of the e...

Impact of human disturbance on bee pollinator communities in savanna and agricultural sites in Burkina Faso, West Africa

“…Bees are key providers of pollination services, which are vital for crop production and food security and the persistence of many wild plants (Klein et al., 2007; Ollerton, Winfree, & Tarrant, 2011). However, many bee species are threatened by land‐use intensification and human disturbance of natural habitats (Ollerton, Erenler, Edwards, & Crockett, 2014; Potts et al., 2010). Land‐use change, such as large‐scale conversion of seminatural habitats to human‐dominated landscapes, can greatly impact bee communities through reduced floral resources (Forrest, Thorp, Kremen, & Williams, 2015) and nesting sites (Shuler, Roulston, & Farris, 2005).…”

Key environmental determinants of global and regional richness and endemism patterns for a wild bee subfamily

“…World-wide reports of pollinator declines (Biesmeijer et al 2006;Williams et al 2009;Potts et al 2010;Cameron et al 2011;Ollerton et al 2014) raise increasing concerns about limitations in seed set and fruit production in agroecosystems (Klein et al 2007;Garibaldi et al 2011a, b). Multiple drivers of wild bee decline can act on various spatial scales ranging from local land-use change and unsustainable agricultural practices (Quintero et al 2009;Brittain and Potts 2011;Rollin et al 2015) to regional biological invasions of pathogens (Cameron et al 2011) and non-native species (Ghazoul 2004), and continental-scale climate change (Hegland et al 2009).…”

Macronutrient ratios in pollen shape bumble bee ( Bombus impatiens ) foraging strategies and floral preferences

“…These resources are accompanied by myriad floral cues, including floral odors, color, morphology, and display area, and can vary dramatically in spatiotemporal availability; all these factors may influence and reinforce foraging decisions (2,3). Worldwide declines in populations of bees and other pollinators have been linked to reduced diversity and abundance of host-plant species, likely placing bees under nutritional stress (4,5). To develop strategic conservation protocols that preserve or restore foraging habitat that supports healthy pollinator populations, we must understand how bees forage in their environments to meet their nutritional needs.…”