A little does a lot : Can small-scale planting for pollinators make a difference?

Donkersley, Philip and Bloom, Elias and Crowder, David (2023) A little does a lot : Can small-scale planting for pollinators make a difference? Agriculture, Ecosystems and Environment, 343: 108254. ISSN 0167-8809

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Abstract

Insect pollinators are declining globally as a result of the anthropogenic pressures that have destroyed native habitats and eroded ecosystems. These declines have been associated with agricultural productivity losses, threatening food security. Efforts to restore habitat for pollinators are underway, emphasizing large-scale habitat creation like wildflower strips, yet ignoring the impact of smaller or more isolated patch-creation. A meta-analysis of 31 independent published studies assessed the effect of scale of pollinator planting interventions (herbaceous strips, hedgerows, fertiliser/grazing/mowing control). We assessed pollinator species richness and abundance against size of intervention and type. Pollinator conservation interventions increased species richness and abundance in almost all of the studies examined, with the greatest increases in pollinator ecological metrics seen from hedgerows covering 40 m² and herbaceous interventions at 500 m². We then analysed results from a 5-year study that deployed small pollinator habitats (30 m²) at community gardens and farms (<150,000 m²) practicing organic methods in the Pacific Northwest US. Small additions to pollinator resources had a significant local impact on pollinator abundance, but this effect was lost when these relatively small additions were introduced to sites in larger landscapes (>150,000 m²). Together, we show that small interventions (∼500 m²) can significantly benefit pollinators, but only when sufficiently densely distributed at a landscape level. Though we understand the effects of single interventions at various scales, future research is needed to understand how these relatively small interventions act cumulatively at a landscape scale, and within this context whether larger areas are still needed for some species. Nonetheless, these preliminary data are promising, and may play an important role in convincing smaller landowners to act to preserve insect pollinators.