Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2021
Publication Date: 9/23/2021
Citation: Helms IV, J.A., Smith, J., Clark, S., Knupp, K., Haddad, N.M. 2021. Ant communities and ecosystem services in organic versus conventional agriculture in the U.S. Corn Belt. Environmental Entomology. 50(6):1276-1285. https://doi.org/10.1093/ee/nvab105.
DOI: https://doi.org/10.1093/ee/nvab105

Interpretive Summary: Certified organic agriculture is a key component of sustainably managing the world's agricultural systems. In one of the largest farming systems in North America, the U.S. Corn Belt, we know little about how organic versus conventional agriculture impact native insects and the ecosystem services they provide. We used long-term (30+ years) experiments to test the benefits of organic agriculture to ant communities and the ecosystem services they provide by foraging on potential crop pests. We found that organic fields supported more ant activity in the early growing season when ant foraging can most benefit crop growth.

Technical Abstract: Reducing the use of synthetic fertilizers and pesticides is a crucial step in global efforts towards sustainable agriculture. In the U.S., organic agriculture has the potential to soften the environmental footprint of the Midwestern Corn Belt—an area extending over 500,000 km2 devoted to intensive production of corn Zea mays, often in rotation with soy Glycine max or wheat Triticum aestivum. Working in 30-year-long experimental landscapes in this region, we tested for impacts of synthetic agricultural chemicals on ant communities and the ecosystem services they provide. Organic fields supported higher ant diversity and a slightly richer ant assemblage than fields managed with chemical fertilizers and pesticides but did not otherwise differ in community composition. Despite similar community composition, organic and chemical fields differed in seasonal patterns of ant foraging activity and the potential for natural pest suppression. Chemical plots experienced higher overall ant foraging activity, but with the timing skewed towards late in the growing season such that 75% of ant foraging occurred after crop harvest in a wheat year and was therefore unavailable for pest suppression. Organic fields, in contrast, experienced moderate levels of ant foraging activity throughout the growing season, with most foraging occurring during crop growth. Organic fields thus supported twice as much pest suppression potential as chemical fields. Our results highlight a novel mechanism mediating ecosystem services in croplands and emphasize the value of managing landscapes for multiple services rather than yield alone.