Eastern North American Monarch Butterfly Conservation Needs and Opportunities: What the Science Tells Us
Oberhauser KS. Insects, February 2026.
Read the paper Free to read · doi:10.3390/insects17030235
What this paper is about
A review of why eastern monarchs have declined since the early 2000s and what would actually help. The three drivers it identifies are loss of milkweed from farmland following the adoption of herbicide-tolerant corn and soybeans, warmer and drier weather, and rising insecticide use.
This is the review that prompted the published exchange with Davis, both halves of which are also in this list.
Summarised here from the abstract below. Not the authors’ words.
Abstract
Monarch butterfly numbers in North America have been declining since the early 2000s. This review focuses on the causes of this decline in the eastern migratory population, found roughly east of the Rocky Mountains, and ways to achieve population sustainability. Drivers of eastern North American monarchs' decline include (1) the loss of breeding habitat, caused mainly by the loss of their milkweed host plants in agricultural fields after adoption of genetically modified, herbicide tolerant corn and soybeans, (2) weather, particularly warmer and drier conditions that could push monarchs farther north and lead to lower numbers, and (3) increasing insecticide use. Making habitat broadly available to monarchs across their migratory cycle will make them more resilient, and better able to survive weather-driven declines, and even small tracts of land can provide needed habitat. Sites that are isolated from other habitat patches contain higher egg, larva, and adult monarch densities. Good monarch habitat should include a diversity of native milkweed species and nectar plants that will thrive in local growing conditions. Monarch egg and larva density increases with increasing milkweed density and monarch survival is higher when larvae are less crowded, so a good general rule is that more milkweed is better.
Abstract reproduced from the published paper, which is licensed CC BY. Copyright remains with the authors.
Key terms
Find the paper
Cite this page
This page is licensed CC BY 4.0. Quote it, adapt it and reuse it, including commercially, as long as you credit Milkweed USA and link back.
Milkweed USA. (2026). Eastern North American Monarch Butterfly Conservation Needs and Opportunities: What the Science Tells Us (listing). Retrieved DATE, from https://milkweedusa.com/research/eastern-north-american-monarch-butterfly-conservation-needs-and-opportunities-2026/
"Eastern North American Monarch Butterfly Conservation Needs and Opportunities: What the Science Tells Us (listing)." Milkweed USA, 2026, https://milkweedusa.com/research/eastern-north-american-monarch-butterfly-conservation-needs-and-opportunities-2026/. Accessed DATE.
Milkweed USA. "Eastern North American Monarch Butterfly Conservation Needs and Opportunities: What the Science Tells Us (listing)." Last modified 2026-08-01. Accessed DATE. https://milkweedusa.com/research/eastern-north-american-monarch-butterfly-conservation-needs-and-opportunities-2026/.
@misc{milkweedusa_researcheasternnorthamerican,
title = {Eastern North American Monarch Butterfly Conservation Needs and Opportunities: What the Science Tells Us (listing)},
author = {{Milkweed USA}},
year = {2026},
url = {https://milkweedusa.com/research/eastern-north-american-monarch-butterfly-conservation-needs-and-opportunities-2026/},
note = {Accessed DATE}
}