New Report: Monarch Butterflies Among 10 Species Imperiled by Pesticides

Use of Glyphosate Eradicates Monarch Caterpillars’ Only Source of Food

WASHINGTON – Chemical pesticides applied to lawns, gardens, and industrial agriculture operations are a major threat to imperiled wildlife, according to a new report released today. “Poisoned: 10 American Species Imperiled by Pesticides” details how daily domestic and commercial pesticides—including herbicides, insecticides, and rodenticides—are contributing to the decline of many species, including monarch butterflies.

Up to one billion monarchs once flew the skies of the continental United States, but their numbers have dropped by 80 percent in the past twenty years due to the use of glyphosate, commonly known as Round Up, which kills milkweed, the monarch caterpillar’s only food source. Most monarchs travel over the country’s agricultural belt in the Midwest, where crops are sprayed with pesticides, killing the milkweed on which monarchs lay their eggs and impairing their ability to reproduce.

“The incessant use of glyphosate and other toxic pesticides threaten the monarch butterfly,” said Sylvia Fallon, Senior Director of the Wildlife Program at NRDC who nominated the monarch butterfly for the report. “The monarch’s migration from Mexico to southern Canada and back again is one of wildlife’s most astounding migrations. These delicate but mighty butterflies travel thousands of miles each year, yet they stand no chance if our government fails to control how Round Up is used.”

Pesticide impacts are felt across the web of life. In the U.S. alone, consumers spend nearly $9 billion annually on pesticides that contaminate the drinking water for as many as 50 million people, according to estimates by the U.S. Department of Agriculture. A 2017 report by the U.S. Fish and Wildlife Service found that two commonly used pesticides (malathion and chlorpyrifos) are so toxic, they jeopardize more than 1,200 endangered species. That report, however, was blocked by political appointees at the Department of Interior, including Secretary David Bernhardt, who now oversees the department. The Trump Administration then overruled Environmental Protection Agency experts and rejected a ban on chlorpyrifos, which is also linked to brain damage in children.

Endangered Species Coalition’s member groups nominated species for the report. A committee of distinguished scientists reviewed the nominations and chose the finalists. The full report, along with photos can be viewed and downloaded at The Endangered Species Coalition produces a Top 10 report annually, focusing on a different theme each year. Previous years’ reports are also available on the Coalition’s website.

Poisoned: 10 American Species Imperiled by Pesticides

  • California red-legged frog
  • Pink mucket pearly mussel
  • Indiana bat
  • San Joaquin kit fox
  • Chinook salmon
  • Crotch's bumble bee
  • Monarch butterfly
  • Northern spotted owl
  • Streaked horned lark
  • Salado salamander
  • Hine’s emerald dragonfly (Staff Pick)

More information on the monarch butterfly:


The Natural Resources Defense Council (NRDC) is an international nonprofit environmental organization with more than 3 million members and online activists. Since 1970, our lawyers, scientists, and other environmental specialists have worked to protect the world's natural resources, public health, and the environment. NRDC has offices in New York City; Washington, D.C.; Los Angeles; San Francisco; Chicago; Bozeman, Montana; and Beijing. Visit us at and follow us on Twitter @NRDC

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