Flower plantings promote insect pollinator abundance and wild bee richness in Canadian agricultural landscapes

Abstract

Abstract: Global declines in pollinator populations are an ongoing concern from biodiversity and food security viewpoints. A growing conservation initiative in agricultural landscapes is the establishment of wildflowers on marginal lands to provide floral resources and habitat for pollinators. However, the effectiveness of such conservation and restoration efforts are not always assessed. We assessed the effectiveness of a private sector pollinator conservation initiative by (1) comparing insect abundance and richness between planted flower plots and control plots and (2) assessing changes between years. Over two years, planted flower plots and control plots (i.e. out-of-production farm areas) located in Canada were surveyed for insects using visual observation, netting, and pan trapping methods. Significantly more pollinators, especially wild bees, and higher wild bee richness were found in planted plots than control plots. Plot size had no effect on insect abundance and richness indicating that even small-scale flower plantings can provide benefits to pollinator communities. While pollinator, predator, and herbivore arthropod abundance and richness were stable or declined between years, likely due to adverse weather conditions in the second year of the study, wild bee abundance and richness increased over the same period. Our results support that flower plantings can be a successful conservation tool to increase pollinator and wild bee abundance and biodiversity within agricultural landscapes.

Implications for insect conservation: Small-scale flower plantings within agricultural landscapes are a simple and effective conservation management strategy to support local insect pollinator populations.

Supplementary information: The online version contains supplementary material available at 10.1007/s10841-022-00400-8.

Keywords: Biodiversity; Conservation; Floral resources; Habitat enhancement; Native bees.

Fig. 1

Study site locations within each province. Stars represent the location of each study site within their respective province and square points represent the location of each pair of treatment and control plots

Fig. 2

Total abundance (A) and richness (B) per plot in 2019 for each group by treatment. Abundance is number of individuals while richness is number of genera for wild bees and otherwise the number of taxonomic families for insect guilds. Black diamond points represent the mean and error bars represent SE. Points are jittered on the x-axis to prevent overlap and improve readability

Fig. 3

Change in abundance (A) and richness (B) between years per group. Abundance is number of individuals while richness is number of genera for wild bees and otherwise the number of taxonomic families for insect guilds. Points represent each plot’s abundance or richness in each year, with lines connecting each plot’s points to help visualize the direction of change between years per plot. Point shape and line color represents province (AB = Alberta, MB = Manitoba, SK = Saskatchewan). Points are jittered on the x-axis to improve readability