Wild pollinators such as bumblebees contribute to crop production.

Credit: Kathy Keatley Garvey/UC Davis

Wild pollinators such as bumblebees contribute to crop production.

Wild bee diversity is declining worldwide at unprecedented rates, and steps must be taken to conserve them — and not just those that are the main pollinators of agricultural crops, declare 58 bee researchers in a study published today (June 16) in the journal Nature Communications.

“This study provides important support for the role of wild bees to crop pollination,” said co-author and pollination ecologist Neal Williams, associate professor in the UC Davis Department of Entomology and Nematology. “At the same time, we found that in any one region, much of the pollination services from wild bees to a given crop come from just a few species, thus we need to be careful about using a simplistic economic ecosystem-services argument for biodiversity conservation and maintain actions that target biodiversity as specific goal.”

Wild, or non-managed bees, include bumble bees (genus Bombus), sweat bees (genus Lasioglossum) and small carpenter bees (genus Cerantina).

The study, led by David Kleijn of Wageningen University, The Netherlands, found that wild bees contribute about $3,251 per hectare ($1.300 per acre) in “crop pollination services,” about the same as the economic contribution from “managed” bee colonies. However, they also found that 80 percent of the crop pollination from wild bees was provided by just 2 percent of wild bee species.

That means that the economic benefit of crop pollination might not be a good argument for conserving wild bee species, according to the authors. Measures taken to protect top pollinators might not benefit wild bee species as a whole.

The paper, “Delivery of Crop Pollination Services is an Insufficient Argument for Wild Pollinator Conservation,” is online at http://www.nature.com/naturecommunications. Among the co-authors are Robbin Thorp, distinguished emeritus professor of entomology at UC Davis, and conservation biologist Claire Kremen of UC Berkeley.