Bee diversity is lower in wealthier Boulder neighborhoods

Impact of wealth and pavement on garden biodiversity.


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The University of Colorado Boulder research revealed a significant finding: community gardens in wealthier Boulder neighborhoods exhibit a lower diversity of bee species than those in medium-income areas. This intriguing disparity could be attributed to the more prevalent use of landscaping practices, such as fertilizers, that directly impact bee habitats.

Asia Kaiser diligently monitored jalapeño plants in Boulder County community gardens. This task underscored the vital role of bees in local ecosystems. Their pollination services are crucial, and the landscape wouldn’t be the same without them.

The result surprised Kaiser and Julian Resasco, the study’s senior author, as it contradicted previous studies. Past studies found wealthier urban areas usually have more trees and green spaces. This attracts a wider variety of animals, known as the luxury effect.

Ecologists Kaiser and Resasco wanted to see how insects in city gardens react to their surroundings. They focused on how urban areas might impact pollinating insects like bees in garden crops.

Last spring, the team planted 70 jalapeño pepper plants in seven extensive community gardens in Boulder and Louisville. They used traps to catch over 3,000 insects and arthropods like spiders from the gardens.

The researchers discovered that neighborhoods with more artificial structures, like pavement and rooftops, had fewer pollinators. Also, wealthier areas had fewer types of bees.

Kaiser explained that landscaping and common plants in wealthier neighborhoods might lower bee diversity. These areas often have mature trees, different from what native bees need. People there might use more pesticides, fertilizers, water, and mulch for these plants, making the soil less suitable for bees to nest in.

Most of the bees in these gardens, like long-horn and squash bees, nest in the ground, so changes in soil affect them. Also, jalapeño peppers grew bigger in gardens with more bee variety, showing how vital pollinators are.

The team found that other arthropods, like beetles and spiders, did well in wealthier neighborhoods. It’s unclear why, but Kaiser thinks they might benefit from the abundance of food in urban gardens.

“It’s interesting how different urban features affect different animals,” Kaiser noted. To boost bee diversity, Colorado residents can plant native plants and provide natural nesting spots like bare soil and wood cover.

The team will study community gardens in Denver to assess pollinator diversity in neighborhoods with varied urbanization and socioeconomic status, including lower-income areas.

Julian Resasco, an assistant professor in the Department of Ecology and Evolutionary Biology and the paper’s senior author, said, “Urban community gardens can be significant sources of nutrition in cities where nutritious food is often hard to come by. Understanding how different aspects of urbanization affect arthropod biodiversity and how that, in turn, affects the yield of these crops is significant.”

Journal reference:

  1. Kaiser, A., Resasco, J. The impact of impervious surface and neighborhood wealth on arthropod biodiversity and ecosystem services in community gardens. Urban Ecosystems. DOI: 10.1007/s11252-024-01560-y.


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