Ecological traits affect the sensitivity of bees to land‐use pressures in European agricultural landscapes

Abstract

Summary Bees are a functionally important and economically valuable group, but are threatened by land‐use conversion and intensification. Such pressures are not expected to affect all species identically; rather, they are likely to be mediated by the species' ecological traits.Understanding which types of species are most vulnerable under which land uses is an important step towards effective conservation planning.We collated occurrence and abundance data for 257 bee species at 1584 European sites from surveys reported in 30 published papers (70 056 records) and combined them with species‐level ecological trait data. We used mixed‐effects models to assess the importance of land use (land‐use class, agricultural use‐intensity and a remotely‐sensed measure of vegetation), traits and trait × land‐use interactions, in explaining species occurrence and abundance.Species' sensitivity to land use was most strongly influenced by flight season duration and foraging range, but also by niche breadth, reproductive strategy and phenology, with effects that differed among cropland, pastoral and urban habitats. Synthesis and applications. Rather than targeting particular species or settings, conservation actions may be more effective if focused on mitigating situations where species' traits strongly and negatively interact with land‐use pressures. We find evidence that low‐intensity agriculture can maintain relatively diverse bee communities; in more intensive settings, added floral resources may be beneficial, but will require careful placement with respect to foraging ranges of smaller bee species. Protection of semi‐natural habitats is essential, however; in particular, conversion to urban environments could have severe effects on bee diversity and pollination services. Our results highlight the importance of exploring how ecological traits mediate species responses to human impacts, but further research is needed to enhance the predictive ability of such analyses.

Diet characterisation of solitary bees on farmland: dietary specialisation predicts rarity

“…Within characterised bees there was a strong relationship between diet breadth and frequency of occurrence, with more generalist species found on a greater number of farms. Whilst earlier studies have shown that generalist bees are less sensitive to agricultural intensification (Bommarco et al 2010;De Palma et al 2015), the level of generalisation has not previously been shown to be a good predictor of frequency of occurrence. As more specialised bees are de facto less flexible in their dietary choices, the loss of floristic diversity resulting from agricultural intensification is likely to be the main driver behind their range declines over the past century (Scheper et al 2014;Ollerton et al 2014).…”

“…However, there are still important knowledge gaps relating to the conservation of wild bees, in part relating to an incomplete understanding of their agro-ecology (Dicks et al 2013). Previous authors have found that bee diet breadth is associated with sensitivity to habitat loss and agricultural intensification, with generalists faring better than specialists (Bommarco et al 2010;De Palma et al 2015). However, much of this analysis has been conducted at the categorical level of generalist or specialist, and it is not clear to what extent the level of generalisation within generalist species is also associated with species persistence.…”

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

“…The inconsistent or insignificant relationships between bee richness and selected land-use variables are probably due to the relatively coarse scale of the analysis used in our study (Rollin et al 2015). To fully understand the effects of land-use change on bee diversity, further data are required on how ecological traits mediate species responses to human pressures (De Palma et al 2015).…”

Analyzing Three-Decadal Patterns of Land Use/Land Cover Change and Regional Ecosystem Services at the Landscape Level: Case Study of Two Coastal Metropolitan Regions, Eastern China

“…As addressed, dramatic LULC change in Greater Shanghai and Greater Hangzhou, particularly recent expansion of developed land at the cost of semi-natural and natural lands, has resulted in a fragmented landscape and unbalanced patterns of ecological services delivery at a regional level, considering the relationship between spatial allocation of ecosystem services and human needs. Some specific ecosystem functions affected by LULC change and landscape fragmentation, such as pollination disturbance, habitat loss, landscape connectivity loss, which can be elaborated with one or several assumptions and empirical interpretations, such as pressures from land-use change and intensification [51,52], species' functional traits influenced sensitivity to human-dominated land use [53], the isolating effects of different patterns [54], and human-induced shifts in the functional structure of biological communities with possible repercussion on important ecosystem functions and services [55]. However, when focusing on interpreting the mechanism underlying the cause-effect relationship between anthropogenic large-scale LULC change, landscape fragmentation, and influenced ecosystems' functioning, the aforementioned assumptions and empirical interpretations may be problematic.…”