Research & reports

Kyla D. Schulte, Caleb J. Wilson, Anna Tawril, Mary A. Jamieson · Ecosphere · United States (Michigan)

A three-year study across 10 strawberry farms along a rural-urban gradient in Michigan, USA, characterized bee abundance, diversity, and community composition. The study found that urbanization, measured as impervious surface cover, had no consistent effect on overall bee abundance and diversity. While urbanization differentially influenced specific taxa (Halictini positively in year one, Ceratinini negatively in year three), the overall impact was limited, with wild bees, especially native species, being important pollinators in urban agriculture.

Alexandra Zink, Paul J. CaraDonna, Kelly Larsen, Amy M. Iler · Ecosphere · United States (Chicago)

This study investigated how urbanization relates to pollination by growing 240 plants (squash and tomato) across six sites with varying urbanization levels in Chicago, Illinois. For tomatoes, the magnitude of pollen limitation increased with greater impervious surface, indicating more pronounced pollination deficits at highly urbanized sites. For squash, evidence of pollen limitation was found only at the most urban site, with a weak trend of pollen limitation of fruit set (but not seed set) increasing with impervious surface.

Sofia Biffi, Cleandho Marcos de Souza, L. G. Firbank · Agriculture Ecosystems & Environment · United Kingdom

Seventeen urban food production sites of varying sizes in and around Leeds, UK, selected from an open-source database, were surveyed using pitfall traps to assess the abundance and diversity of epigeal invertebrates (beetles, springtails, and spiders) in relation to soil characteristics (organic carbon, moisture content, pH) and site area; soil productivity was assessed by growing radish (Raphanus sativus) under uniform conditions. The study found no correlation between epigeal invertebrate abundance or diversity and either site area or soil characteristics. The authors state this indicates there is, as yet, no evidence that urban food production sites are too small to draw on ecosystem services delivered by epigeal invertebrates.

Kevin C. Matteson, Gail Langellotto · Insect Conservation and Diversity · United States (New York City)

The ability of adding 70 plants of seven native wildflower species over two years to augment beneficial insect richness, including bees, butterflies, and predatory wasps, was assessed in New York City community gardens. Bayesian analyses failed to find a strong influence of the native plant additions on beneficial insect richness, even after correcting for prior floral abundance. Butterflies and megachilid bees were found to heavily utilize introduced ornamental and crop flowers in these gardens, even when native flowers were present.