The monarch is one of the best-known and most beloved butterflies in North America, occurring throughout a broad range of habitats across the U.S. and into southern Canada and central Mexico. Two populations migrate to overwintering sites each fall: monarchs east of the Rocky Mountains migrate primarily to high-elevation forests in central Mexico, while most monarchs west of the Rockies migrate to hundreds of smaller, wooded groves along the California coast. Yet, this once-common butterfly now faces an uncertain future, with annual monitoring of overwintering monarchs in central Mexico and along the California coast revealing significant population declines. In the 1990s, estimates of up to one billion monarchs made the epic flight each fall to Mexico, and more than one million monarchs overwintered in forested groves along the California coast. Now, researchers and citizen scientists estimate that only a fraction of the population remains. A decline of more than 80% has been seen in central Mexico and a decline of 74% has been seen in coastal California (see graph below).
The conservation status of monarchs and the threats to their populations in the eastern U.S. have been thoroughly researched, but much less is known about the monarch population west of the Rocky Mountains. In particular, the locations and quality of existing monarch breeding sites in the West are generally unknown. In the eastern U.S., researchers have identified loss of milkweed as the most significant factor contributing to the observed declines of monarchs overwintering in Mexico. It is thought that loss and degradation of monarch breeding sites in the West has triggered similar declines observed at the California overwintering sites. However, before this can be assessed, we must understand where these important breeding locations are within the Western landscape. Initial modeling work published in 2010 identified probable breeding habitat in most of California; western Nevada; Arizona; and isolated regions of Oregon, Washington, Utah, and Idaho. A recent isotopic study at four overwintering sites in California suggests that the natal origin of a large portion of overwintering monarchs is from coastal Southern California and Oregon, Washington, and Idaho. Both of these studies have highlighted large key areas to target; however, data are needed at a finer scale in order to effectively plan conservation and restoration work on the ground.
Conservation at Work
The Xerces Society and our partners are working to protect and manage the habitats that support all life stages of the monarch’s life cycle. We work at both national and regional scales to promote monarch conservation efforts. In the West this includes holding workshops for land managers, training biologists and volunteers to conduct surveys for milkweed breeding habitat, developing citizen science programs and tools to better address conservation issues specific to western monarchs, and restoring habitat. See our monarch conservation update for a summary of recent efforts and ongoing partnerships and learn more on our Monarch page.
Are you interested in supporting monarch conservation? There are a number of ways you can contribute, too!
- Take photos of monarchs and milkweeds in your area and submit your sightings to the Western Monarch Milkweed Mapper.
- Identify existing monarch habitat (which may include milkweed host plants, nectar plants, water sources, or roosting trees) and protect it!
- In areas where milkweed and nectar plants have been lost, consider creating or restoring habitat. Monarchs need nectar-rich flowers as adults and milkweeds for their young. Find monarch nectar plant lists and milkweed seeds for your region.
- Join the Bring Back the Pollinators Campaign and sign the Pollinator Protection Pledge!
- Support local and organic agriculture. Many insecticides and herbicides can be harmful to monarchs and milkweeds.
- Spread the word! Let your friends and family know you are contributing to monarch conservation and encourage them to participate too!
- Want to contribute to more citizen science projects? Check out some of the other projects occurring all over the country.