The U.S. state of California has instituted numerous conservation programs, policies, laws, reserves and habitat restoration projects throughout the state to facilitate the health and migration of the western population of the monarch butterfly (Danaus plexippus). A Scientific Collecting Permit (SCP) is required to handle wild monarchs in California including for educational purposes. It is unlawful to collect, remove from the wild and/or captively rear monarchs in California without an SCP. The population of western monarchs require very different breeding and overwintering habitat when compared to the eastern population of monarch butterflies. They require specific micro-climatic conditions to survive the winter and they are sensitive to habitat changes at the overwintering sites. The large aggregations of butterflies are seen as the most vulnerable at their overwintering locations along the coast. Many monarch overwintering sites are contained within the "coastal zone"; an area defined by the Coastal Zone Management Act to be 1000 yards inland from the high tide mark. Large number of overwintering sites are outside the coastal zone. There are more than 450 overwintering sites in California.
Habitat conservation Conservationists promote habitat conservation by identifying trees that are necessary for roosting. They suggest that roosting sites be identified and designed to prevent degradation of the area. They also suggest that an environmental impact statement be filed when construction is done near overwintering roasts. Removal of trees within the perimeter of the habitat should be prohibited. Tree maintenance should be performed by experts in the field. They propose that it should be unlawful to remove trees, under-story plants and vegetation near roosting sites. Reforestation efforts should be instituted. Erosion control needs to be taken into account to maintain suitable habitat. Conservationists suggest that wood-burning fireplaces and structures should not be built near roosting sites. The International Environmental Law project issued a policy statement regarding eucalyptus management at monarch overwintering sites. This group recognizes the wide variety of tree species that monarchs utilize in their overwintering roosts. The Xerxes society recommends that eucalyptus trees remain unmolested, if monarchs roost on the trees.
Proposed conservation measures The International Environmental Law Project of 2012 has proposed model legislation and recommends the following:
Amend the California Fish and game regulations to authorize the California Department of Fish and game to regulate the monarch butterfly. Amend the California endangered species act to include the monarch butterfly. Amend the coastal act to specifically recognize overwintering sites as needing special protection. Continue discussion via the Trilateral Committee for Wildlife and Ecosystem Conservation and Management Summit to organize continent wide conservation actions. Limiting activities at the overwintering sites (logging, tourism). Mass planting of milkweed and nectar plants. Concerned individuals governmental agencies, and organizations have made efforts to restore milkweed habitats to provide nectar and food plants. Studies that involve the participation of citizen-scientists who monitor and apply tags to migrating monarchs Lobbying lawmakers, corporations, highway departments, utilities and policy-makers to preserve habitat. The continued acquisition of land for the expressed purpose of monarch conservation. On December 12, 2024, the United States Fish and Wildlife Service (USFWS) published in the Federal Register a proposed rule that would list the monarch butterfly (Danaus plexippus) as a threatened species and would designate the butterfly's critical habitat per the provisions of the Endangered Species Act. The USFWS estimated in the proposed rule that the probability of extinction in the foreseeable future (60 years) is 56-74 percent for the eastern monarch migratory population and 99 percent for the western migratory population. The proposed rule designated seven areas near California's Pacific coast as "critical habitat units" for monarch butterflies. The USFWS accepted comments on the proposed rule until March 12, 2025. On March 19, 2025, the USFWS reopened the comment period on the proposed rule until May 19, 2025.
Habitat restoration Participants in Monarch Watch's waystation program have planted acres of native milkweeds to encourage larval growth for monarchs. These way stations also provide nectaring plants for adult monarchs.
Tree management Most locales do not have laws or policies concerning the removal or alteration of trees within a designated monarch overwintering site. Alteration of trees requires a permit in Capitola and Goleta. Studies continue to determine the efficacy of the continued use of eucalyptus trees as roosting trees. Large gaps in the tree canopies at the overwintering sites in California affect the suitability of the roosts.
Overwintering sites Large number of overwintering sites are outside the coastal zone. There are more than 450 overwintering sites in California documented since the 1980s.
California state parks and lands
Monarchs are protected from the effects of land development, tourism in the 270 California state parks. The activities of visitors to the parks are regulated to include the prohibition of molesting, hunting, disturbing, harming, feeding, touching, teasing, injuring, trapping, taking, netting, poisoning any animal or trees. The collecting, capturing and killing of any animals and the destruction of native vegetation is prohibited in the parks. Overwintering sites occur near beaches, universities and other state lands. State parks do not have specific policies regarding the maintenance of trees on which the monarchs overwinter. California historical sites are exempt from having to create monarch conservation plans. Twenty state parks contain monarch overwintering groves.
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