Increasing the conservation value of powerline corridors for wild bees through vegetation management: an experimental approach

K N Russell,S Kornbluth,G J Russell,K L Kaplan,S Mian

doi:10.1007/s10531-018-1552-8

Abstract

Mounting evidence suggests declines in the abundance and diversity of wild bees. Increasing habitat that provides forage and nesting sites could boost struggling populations, particularly in urban, suburban and agricultural landscapes. The millions of acres beneath aerial electric transmission lines, sometimes referred to as easements or rights-of-way, must be kept free of tall-growing vegetation and hence have the potential to provide suitable habitat for many native species. Prior work has demonstrated that bee communities in easements managed using alternatives to episodic mowing were more diverse than in nearby open areas, however true control sites within the easements were unavailable. In order to compare vegetation management protocols, we conducted a two-year study which enabled us to directly compare transmission line easements in three locations currently undergoing Integrated Vegetation Management—a dynamic form of management involving spot removal and herbicide treatment of unwanted species (treatment) with nearby sites undergoing standard management protocols of yearly or biyearly mowing (control). Results show that treatment sites had significantly higher abundance and species richness than controls. Seasonal differences were pronounced, with the spring fauna most affected by differences in vegetation management. In addition, the older treatment sites house more social bees, more parasitic species and a more even distribution of bees across nesting guilds. Finally, we established that treatment sites had distinct bee communities, further increasing their value as sources for native bee populations in the landscape. Overall, the data clearly show the value of implementing alternative active vegetation management in the land under powerlines to achieve an increase in the abundance and diversity of wild bees.

Highlights

Public interest in the health of wild bee communities has primarily stemmed from concerns surrounding the provision of pollination services for agriculture, exemplified by President Obama’s Presidential Memorandum back in 2014 mandating a federal effort to promote the health of pollinators in the United States
Despite their significance as a group, it is true that not all bee species are adept at or needed for sufficient pollination of crops (Kleijn et al 2015) and a greater diversity of bees has been implicated in increased pollination services (Fontaine et al 2005; Perfectti et al 2009) and functional redundancy in pollinator networks leading to more stable pollination services (Kaiser-Bunbury et al 2017), it would be misguided to focus only on agricultural economics
Transmission line easements provide these resources, when they are managed in a dynamic, integrated way that promotes a healthy mix of shrubs and herbaceous plants

Summary

Introduction

Public interest in the health of wild bee communities has primarily stemmed from concerns surrounding the provision of pollination services for agriculture, exemplified by President Obama’s Presidential Memorandum back in 2014 mandating a federal effort to promote the health of pollinators in the United States. The focus on pollination services makes sense considering that the economic value of these services is estimated to be between 100 and 200 billion dollars per year worldwide (Gallai et al 2009; Klein et al 2007). Not all these animal pollinators are bees (Rader et al 2016), bees have been shown to be the most important animal pollinators of agricultural crops worldwide (Williams et al 2001). Focus has traditionally been on managed honeybees (Apis mellifera), but recent analyses have shown that wild bees as a group contribute roughly the same amount to crop pollination (Kleijn et al 2015). Ollerton et al (2011) estimates that 74% of all plant species in temperate biomes and 94% in tropical areas are serviced by animal pollinators, a majority of which are bees (Williams et al 2001), healthy native plant communities require healthy bee communities

Objectives

Methods

Results

Discussion

Conclusion