Opinion: California plays a central role in monarch butterfly’s survival

With the recent proposed listing of the monarch butterfly under the Endangered Species Act, the U.S. Fish and Wildlife Service has taken a critical step to protect one of North America’s most beloved species.

This decision reflects overwhelming scientific evidence that monarch populations have plummeted, primarily due to habitat loss, climate change and widespread pesticide use. Protecting monarchs — and other pollinators we depend on for healthy ecosystems and food production — will require bold action.

While the proposed listing is a victory for conservation, it is just the first step. Now the Environmental Protection Agency must step up and do its part. In its proposal to list the monarch as a threatened species, the Fish and Wildlife Service identifies pesticide exposure as a threat to their continued survival. Monarchs cannot recover without stronger protections from pesticides.

California plays a central role in this story. Western monarchs rely on overwintering groves along the California coast, some of which are now proposed to be designated as critical habitat for the species. And many rely on migratory and breeding habitat in the Central Valley, where milkweed, the sole food source for monarch caterpillars, is often contaminated with pesticides. This combination of overwintering, migratory and breeding habitat makes California one of the most critical regions for monarch survival. Yet it is also one of the regions where pesticide exposure poses a significant threat.

On Dec. 17, on behalf of the Xerces Society for Invertebrate Conservation, Earthjustice formally petitioned the EPA to close critical gaps in how it assesses pesticide risks to pollinators. These gaps have allowed pesticides to be overused and under-regulated, putting pollinators and other beneficial insects at risk.

The EPA is required by law to prevent “unreasonable adverse effects” of pesticides on the environment, including harm to wildlife. It must assess risks before a new pesticide can go to market. However, when it comes to pollinators, the EPA relies heavily on limited information about a single species: the European honey bee. Honey bees are important, but they do not adequately represent the over 3,600 native bee species in the United States, let alone completely different groups of insects, such as butterflies. The result is that the EPA vastly underestimates the harm from pesticides to important pollinators. Without this basic information, our ability to make informed decisions on how to protect monarchs and other pollinators from pesticide exposure is limited.

We know this is a problem. Research in California’s Central Valley by the Xerces Society and University of Nevada-Reno detected 64 different kinds of pesticides in milkweed leaves, the food source for monarch caterpillars. One of these, called methoxyfenozide, is likely to be highly toxic to caterpillars and was in 96% of milkweed samples, but it is classified as “practically non-toxic” to adult honey bees. Without standard testing on butterflies, pesticides such as methoxyfenozide can be registered and used without adequate safeguards.

The EPA must take the monarch listing proposal seriously so that its pesticide decisions do not jeopardize monarch recovery efforts. We urge the EPA to adopt strong, scientifically defensible requirements for toxicity testing on pollinators beyond honey bees. By addressing these gaps now, the EPA has an opportunity to strengthen protections for all wildlife threatened by pesticides, from insects to the many birds, fish and mammals who depend on them for food.

Other countries have already demonstrated that this is achievable. The European Food Safety Authority has advanced risk assessment frameworks that consider a broader range of species. The United States must follow suit.

The plight of the monarch butterfly is an opportunity to seriously reexamine the role of pesticides in biodiversity loss. We have reached a critical moment for the EPA to require more complete information and testing on the pesticides used in our environment so that we can create a strong future for people, wildlife and agriculture.

Rosemary Malfi is director of conservation policy at The Xerces Society for Invertebrate Conservation. Sharmeen Morrison is an attorney for the Biodiversity Defense Program, Earthjustice.