New synthesis by Iowa State University researchers presents risks and benefits of monarch conservation practices in agricultural landscapes

monarch on flower in field
Photo by Jacque Pohl

AMES, Iowa – New research on monarchs published by Iowa State University scientists in the peer-reviewed journal, BioScience, offers encouraging insights for revival of monarch populations.

The paper concludes that the population of breeding monarchs in Iowa and other north central states could increase by up to 10 to 25% per generation if progress in implementing monarch conservation plans continues to stay on track, even with current agricultural land-use patterns.

These findings are based on the results of a six-year, multi-disciplinary Iowa State research project designed to determine how habitat fragmentation, spatial configuration of habitat, habitat quality, and pesticide use in a landscape dominated by corn and soybean production, interact with patterns of monarch movement and life stage survival, to influence the size of the eastern monarch's breeding population.

Strategic placement of new habitat parcels will be one key to monarch recovery, according to the research. The ISU research suggests a pattern of approximately seven acre habitat tracts containing milkweed and wildflowers placed at 150 to 350 feet intervals are optimal for monarch reproduction, even when the habitat is established next to crop fields treated with insecticides.

The paper emphasizes that the population increases projected also depend on implementation of commonly recommended integrated pest management practices and spray drift mitigation measures.

The research helps answer important questions related to the long-term survival of North America's eastern monarch butterfly, which is under consideration for listing as a threatened or endangered species by the U.S. Fish and Wildlife Service.

Establishing habitat, especially milkweed, is key to reversing the species' decline and assuring its long-term survival. That includes creating habitat in agriculturally dominated areas of the North Central U.S., which is the monarch's prime breeding grounds, where foliar and seed‐treatment insecticides are routinely used on crop fields from May to August, coinciding with peak levels of monarchs in the region.

The Iowa State research team used a modeling-based approach to design and implement a multi-layered research project to determine how the amount and configuration of habitat and pesticide use patterns interact to influence monarch butterfly populations in their summer breeding range. The research effort included development of a model that simulates female movement and egg-laying that is linked to another model that predicts survival of monarch eggs and larvae. The development and evaluation of these models were informed by results of laboratory and field-based research on monarch life history, movement ecology, and pesticide toxicology. The overview publication synthesizes results from 20 peer-reviewed papers authored by members of the ISU team, along with findings from other monarch researchers in North America and Australia.  

Sources of support for the ISU team's research included the United States Department of Agriculture/National Institute of Food and Agriculture/Agriculture and Food Research Initiative/ Pollinator Health Program, the Iowa Agriculture and Home Economics Experiment Station and College of Agriculture and Life Sciences, the USDA Agricultural Research Service, the Iowa Monarch Conservation Consortium, the Garden Club of America Centennial Pollinator Fellowship, the Holohil Grant Program, the Xerces Society and Prairie Biotic Research.



Steven Bradbury, Natural Resource Ecology and Management, 515-294-7315,

Nicole Shimp, Iowa Monarch Conservation Consortium, 515-294-9227,