Conservation risks and benefits of establishing monarch butterfly (Danaus plexippus) breeding habitats close to maize and soybean fields in the north central United States: A landscape-scale analysis of the impact of foliar insecticide on nonmigratory monarch butterfly populations
Grant TJ, Krishnan N, Bradbury SP. Integrated environmental assessment and management, May 2021.
Go to the paper May need a subscription · doi:10.1002/ieam.4402
What this paper is about
One suggested way to protect monarchs is to avoid planting milkweed within 38 m of a crop field. In Story County, Iowa, that rule would rule out 84 percent of roadsides and 38 percent of non-crop land.
The analysis weighs the habitat lost by applying the buffer against the insecticide exposure avoided by it.
Summarised here from the abstract below. Not the authors’ words.
Abstract
Establishing habitat in agricultural landscapes of the north central United States is critical to reversing the decline of North America's eastern monarch butterfly (Danaus plexippus) population. Insecticide use could create population sinks and threaten recovery. Discouraging habitat establishment within a 38-m zone around crop fields is a suggested risk mitigation measure. In Story County, Iowa, United States, this mitigation would discourage habitat establishment in 84% of roadsides and 38% of noncrop land. It is unclear if the conservation benefits from establishing habitat close to crop fields outweigh suppression of population growth owing to insecticide exposure. Consequently, monarch conservation plans require spatially and temporally explicit landscape-scale assessments. Using an agent-based model that incorporates female monarch movement and egg laying, the number and location of eggs laid in Story County were simulated for four habitat scenarios: current condition, maximum new establishment, moderate establishment, and moderate establishment only outside a 38-m no-plant zone around crop fields. A demographic model incorporated mortality from natural causes and insecticide exposure to simulate adult monarch production over 10 years. Assuming no insecticide exposure, simulated adult production increased 24.7% and 9.3%, respectively, with maximum and moderate habitat establishment and no planting restrictions. A 3.5% increase was simulated assuming moderate habitat establishment with a 38-m planting restriction. Impacts on adult production were simulated for six representative insecticides registered for soybean aphid (Aphis glycines) management. Depending on the frequency of insecticide applications over a 10-year period, simulated production increased 8.2%-9.3%, assuming moderate habitat establishment with no planting restrictions. Results suggest that the benefits of establishing habitat close to crop fields outweigh the adverse effects of insecticide spray drift; that is, metapopulation extirpation is not a concern for monarchs. These findings are only applicable to species that move at spatial scales greater than the scale of potential spray-drift impacts. Integr Environ Assess Manag 2021;17:989-1002. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).
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Milkweed USA. (2026). Conservation risks and benefits of establishing monarch butterfly (Danaus plexippus) breeding habitats close to maize and soybean fields in the north central United States: A landscape-scale analysis of the impact of foliar insecticide on nonmigratory monarch butterfly populations (listing). Retrieved DATE, from https://milkweedusa.com/research/conservation-risks-and-benefits-of-establishing-monarch-butterfly-danaus-2021/
"Conservation risks and benefits of establishing monarch butterfly (Danaus plexippus) breeding habitats close to maize and soybean fields in the north central United States: A landscape-scale analysis of the impact of foliar insecticide on nonmigratory monarch butterfly populations (listing)." Milkweed USA, 2026, https://milkweedusa.com/research/conservation-risks-and-benefits-of-establishing-monarch-butterfly-danaus-2021/. Accessed DATE.
Milkweed USA. "Conservation risks and benefits of establishing monarch butterfly (Danaus plexippus) breeding habitats close to maize and soybean fields in the north central United States: A landscape-scale analysis of the impact of foliar insecticide on nonmigratory monarch butterfly populations (listing)." Last modified 2026-08-01. Accessed DATE. https://milkweedusa.com/research/conservation-risks-and-benefits-of-establishing-monarch-butterfly-danaus-2021/.
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title = {Conservation risks and benefits of establishing monarch butterfly (Danaus plexippus) breeding habitats close to maize and soybean fields in the north central United States: A landscape-scale analysis of the impact of foliar insecticide on nonmigratory monarch butterfly populations (listing)},
author = {{Milkweed USA}},
year = {2026},
url = {https://milkweedusa.com/research/conservation-risks-and-benefits-of-establishing-monarch-butterfly-danaus-2021/},
note = {Accessed DATE}
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