Monarch butterflies (Danaus plexippus plexippus) are perhaps the most well-known and beloved butterflies species in North America. A ubiquitous sight in gardens, prairies, and natural areas from coast to coast, their arrival in northern states and Canadian provinces is viewed by many as a welcome sign of the change in seasons from spring to summer. Renowned for their long-distance seasonal migration and spectacular winter gatherings in Mexico and California, the monarch butterfly population has recently declined to dangerously low levels.
An epic migration, on the verge of collapse.
In the 1990s, nearly 700 million monarchs made the epic flight each fall from the northern plains of the U.S. and Canada to sites in the oyamel fir forests north of Mexico City, and more than one million monarchs overwintered in forested groves on 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 97% has been seen in coastal California.
Monarchs require suitable habitat that provides host plants for breeding and flowering plants to provide nectar for adults. In the case of monarchs, the loss of milkweed means the loss of breeding habitat. Loss of milkweed from prime migration routes is primarily due to the dramatic increase in the use of the herbicide resistant crops Commonly known as Roundup™ Ready Crops, these corn and soy crops are genetically modified to be resistant to glyphosate, a broad-spectrum herbicide that kills everything other than the resistant crop, including milkweed. Harsher winters in monarch overwintering sites have caused larger than usual die-offs. Erratic weather may also delay the emergence of milkweed in spring and change the bloom time of flowering plants that provide resources to migrating monarchs. Legal and illegal logging in the oyamel fir forests of Mexico where eastern monarchs overwinter has removed important winter cover for the species and impacted microclimates that protect the butterflies from extreme cold and precipitation. In California, many sites where western monarchs overwinter have been lost due to development.
In the three decades since first standing up for monarchs, the Xerces Society has gained extensive experience and accumulated expertise in all aspects of monarch conservation. Our work now extends to protecting and managing the habitats that support all stages of the monarch’s lifecycle throughout the transcontinental range of the butterfly’s migration. See our monarch conservation update for a summary of our recent efforts and ongoing partnerships.
Monarchs in the West
An analysis in Xerces’ newly released report, State of the Monarch Butterfly Overwintering Sites in California, shows a 74% decline in the California overwintering population in less than 20 years, comparable to declines observed in the monarch population that overwinters in Mexico. The Xerces Society has been working to ensure that the western monarch population is included in monarch conservation efforts. Xerces has been working on many fronts, holding workshops to assist land managers in identifying monarch conservation needs, training biologists and volunteers to conduct surveys for milkweed breeding habitat, and developing citizen science programs and tools to better address conservation issues specific to western monarchs.
Project Milkweed and Milkweed Seed Finder
Monarchs need milkweed! Find resources for growing milkweed and locate seed using our Milkweed Seed Finder. Learn more
Monarch Nectar Plant Guides
Are you interested in gardening for monarch butterflies? Find out which plants are the best nectar sources for monarchs in your area. Learn more
- Managing Monarchs in the West: Best Management Practices for Conserving the Monarch Butterfly and its Habitat
- Conservation Status and Ecology of the Monarch Butterfly in the United States
- State of the Monarch Butterfly Overwintering Sites in California
- Protecting California’s Butterfly Groves: Management Guidelines for Monarch Butterfly Overwintering Habitat
- July 2016 Monarch Update: Helping Monarch Conservation Take Flight
- Petition for Protection of the Monarch Butterfly Under the Endangered Species Act
- Joint Statement Regarding Captive Breeding and Releasing of Monarchs
- Milkweeds and Monarchs in the Western U.S.
- Report: Monarch Butterfly Site Management Plan for Lighthouse Field State Beach
Partners and Sponsors
The Xerces Society’s work to protect monarch butterflies and other pollinators has been made possible with generous support from the Alice C. Tyler Perpetual Trust, Audrey & J.J. Martindale Foundation, Aveda, Cascadian Farm, Ceres Trust, Cheerios, Clif Bar Family Foundation, CS Fund, Disney Conservation Fund, Endangered Species Chocolate, LLC, Gaia Fund, General Mills, Hind Foundation, Idaho Department of Fish and Game, Iowa Department of Transportation’s Living Roadway Trust Fund, Irwin Andrew Porter Foundation, J.Crew, National Co+op Grocers, National Fish and Wildlife Foundation, Nature Valley, Nestlé Dreyer’s Ice Cream Company, Sarah K. de Coizart Article TENTH Perpetual Charitable Trust, SeaWorld & Busch Gardens Conservation Fund, Swimmer Family Foundation, The Bay and Paul Foundations, The Dudley Foundation, The Edward Gorey Charitable Trust, The Elizabeth Ordway Dunn Foundation, The Monarch Joint Venture, The New-Land Foundation, Inc., The Oregon Zoo Foundation, The White Pine Fund, Turner Foundation, Inc., U.S. Department of Agriculture Natural Resources Conservation Service, U.S. Department of Agriculture Sustainable Agriculture Research and Education, U.S. Department of the Interior Fish and Wildlife Service, U.S. Geological Survey, Whole Foods Market and its vendors, the Whole Systems Foundation, and Xerces Society members.