Organic management enhances wild bee richness but does not consistently improve crop pollination in apple orchards

Abstract

Organic agriculture is considered a more biodiversity-friendly alternative to conventional agriculture, the latter being a major driver of biodiversity loss. Perennial woody crops, like apple, provide nutritious food for humans and stable habitats for biodiversity. Yet, a synthesis of the effects of organic management on pollinators and pollination has not been done in this crop. Here, we synthesized data from seven studies to assess how organic versus non-organic management in apple cultivation influences bee communities (honeybee abundance, wild bee abundance, and species richness), and pollination (fruit set, fruit weight, and seed set). Organic management increased wild bee richness but had no effect on honeybee or wild bee abundance. Fruit set was unaffected by management or bee metrics. Fruit weight was lower under organic management and decreased with increasing honeybee abundance. Seed set was higher under organic management, and the effects of both wild bee abundance and species richness on seed set were management dependent, as we concluded a positive relationship between wild bees and seed set in non-organic orchards, whereas no effect was detected in organic orchards. We conclude that organic management supports greater bee richness in apple orchards, and effects on pollination vary between the considered pollination metrics. These findings challenge the expectation that organic management has a general positive effect on pollinators and their pollination services. We suggest avoiding excessively high honeybee densities as they may negatively affect pollination. Our study underscores the need for more research on more specific management actions that benefit pollinators, pollination and yield in order to develop management strategies that simultaneously enhance ecological and agronomic outcomes.