Protection for monarch butterflies: Potential benefits and risks

Monarch butterflies are a beloved species in North America, known for their colorful appearance and incredible migration. Each fall, monarchs travel to specific sites in central Mexico and coastal California to overwinter. These areas provide a balance of temperatures that prevent the butterflies from freezing or burning too much energy.

However, over the past 40 years, monarch populations have declined significantly. Monarchs overwintering in Mexico have dropped by 80 percent between 2007 and 2023, and those in California by over 95 percent. As a result, the U.S. Fish and Wildlife Service is considering listing monarchs as a threatened species under the Endangered Species Act, with public comments open until March 12, 2025.

The primary concern is the decline in monarch numbers at overwintering sites, particularly in Mexico. Several factors contribute to this, including a parasite that affects monarchs' health, roadkill, climate change altering migration patterns and some monarchs not migrating due to warmer weather.

Interestingly, studies show monarchs are still abundant in their summer breeding range. A 2022 study revealed no overall decline in monarch numbers, and a 2023 genetic study also found no population decline. Habitat destruction from agriculture appears to have even increased available habitat for their host plants, such as milkweed.

The monarchs' ability to rebound during the breeding season, where females lay hundreds of eggs, helps maintain their population despite declines in overwintering numbers.

To address these issues, the U.S. Fish and Wildlife Service proposes protecting winter habitats and planting appropriate flowering plants along migration routes. However, there are concerns about some proposed actions, such as raising butterflies in captivity or planting nonnative milkweed, which could worsen the situation due to disease spread and migration disruption.

Experts agree that conservation efforts should focus on improving migration routes and wintering sites rather than captive breeding or planting milkweed in summer ranges. While monarchs are valuable as conservation symbols, actions not based on scientific evidence could inadvertently harm their populations.

(Cover: A monarch butterfly. /CFP)