Among a number of organizations, the Center for Biological Diversity has long warned of the decline and potential extinction of the migrating populations of monarchs. The dire predictions are based on the finding that more than 80% of monarchs east of the Rocky Mountains have disappeared in the last 20 years. The much smaller western population, west of the Rockies and wintering in southern California where they cluster on eucalyptus trees as well as pines and cypress along the coast, has declined by a devastating 95%.
In Mexico, the mountain forests are threatened by clearing for agriculture, as well as illegal logging. With these forests in danger, the Mexican government in 1986 created the Monarch Butterfly Biosphere Reserve (Reserva de Biosfera de la Mariposa Monarca) and expanded it in 2000. Stricter enforcement has virtually eliminated large-scale illegal logging, but small-scale, sometimes only one tree at a time, is still a concern.
In 2008, UNESCO declared the reserve a World Heritage Site. Still, the felling of forests outside protected areas for agriculture allows strong winds and storms to penetrate the core areas where the monarchs gather. The combination of cold and damp can prove lethal.
In a more serious threat to the migration, food sources are disappearing in the U.S. through which the eastern population must travel. Conversion of native prairie to agriculture, roadside mowing, herbicide use, and development all eliminate milkweed and other native plants that provide essential food for the butterflies and their caterpillars. And as with most natural systems, any threat is now exacerbated by climate change as the mid-continent dry plains slowly creep eastward. Warming temperatures also may be throwing off the timing of monarch migration with emergence of milkweed that has existed for millennia.
In the past, milkweed and native wildflowers at least thrived along field margins, which helped the monarchs make the journey. However, with the development of genetically modified corn and soybean crops that resist herbicides, there’s been an increased use of glyphosate, also known by the brand name Roundup®, which kills broadleaf weeds and grasses, including any milkweed within reach when the herbicide is sprayed on fields.
Glyphosate is registered as a pesticide and so subject to a registration review every fifteen years. In February 2020, the EPA issued an interim decision on a new registration review of glyphosate, saying they found no risks “of concern” to human health if used as directed, despite independent studies linking glyphosate to cancer. The EPA also discounted potential ecological damage, such as from spray drifting to non-target plants, saying the benefits of glyphosate’s use outweigh the risk.
The next month, conservation and health groups led by the Natural Resources Defense Council sued, stating the EPA had not adequately addressed the environmental damage and the risk of cancer, the latter disproportionately impacting the poor and people of color who make up the majority of fieldworkers. During this period, the EPA had been conducting a biological evaluation of glyphosate, released in November 2021, that found 93% of endangered species are likely harmed by glyphosate and 96% of critical habitat is likely adversely affected.
In June 2022, the U.S. Court of Appeals agreed with the plaintiffs on the challenge to the interim decision on glyphosate. So in September 2022, EPA announced it was withdrawing the interim decision and that it would conduct a new review of glyphosate’s effects, especially on the environment. Completion of the review will likely take a couple of years to complete, and in the meantime, the chemical is still being used.
Herbicides and pesticides pose a double threat. While glyphosate applications kill the monarch’s host plant, pesticides kill the monarchs and their caterpillars outright. The family of pesticides known as “neonics” (neonicotinoids) are lethal neurotoxic insecticides that have become the most common pesticides applied on agricultural crops and grass lawns. As the grass or the crops grow, the plants take up the neonics, making the plant itself toxic. Neonics are long lived and can migrate through the soil, contaminating other areas and plants. So if a milkweed takes up a neonic, it becomes toxic and the caterpillar munching on a leaf will be poisoned. And the toxin taken up by a plant appears in the plant’s nectar, so adult butterflies, bees, and even birds are also killed outright, not to mention the threat to human health as we ingest neonic-treated vegetable, fruit, and grain crops. Research has linked neonics to a variety of neurological issues. At this writing, the EPA is expected to endorse continued widespread use of neonics, rather than the total ban on these pesticides that is needed to protect our health and ecosystems.
Some progress is being made for the conservation of monarchs, primarily by the federal government and NGOs. State agencies that have the lead in protecting wildlife within each state are hampered by legal definitions of “wildlife” that do not include insects. Consequently, state wildlife agencies typically cannot spend state funds on insect conservation.
In 2020, an agreement was reached with more than 45 transportation and energy companies, as well as private landowners, for a program to protect monarch habitat. The Fish & Wildlife Service partnered with the University of Illinois at Chicago for the university’s Energy Resources Center to administer the program. The agreement encourages transportation and energy partners to participate in monarch conservation by providing and maintaining habitat on rights-of-way on both public and private lands across the country.
Measures to protect pollinators were incorporated in the Infrastructure Investment and Jobs Act that became law in November 2021. Funding of $10 million was included in the Fiscal Year 2023 federal budget for the western population that includes $3 million from the Monarch and Pollinator Highway Program that was created as part of the Act.
The effort to save monarchs includes the work of a number of nongovernmental organizations that have been active for years specifically to preserve the monarch and other pollinators. Farmers for Monarchs joins farmers, ranchers, and other landowners as well as businesses, researchers, and government agencies to encourage agricultural operations that preserve monarch habitat, urging farmers with marginal croplands to enroll that acreage in state and national conservation programs. Monarch Joint Venture builds partnerships to conserve monarchs and other pollinators. One of MJV’s projects, the “Monarch Highway,” joins the states through which I-35 travels from Minnesota to Texas in a partnership to preserve pollinator habitat.
Among all things monarch, Monarch Watch at the University of Kansas, founded in 1992 by Chip Taylor and Brad Williamson, provides for monarch tagging as well as tag recovery along the migratory routes. Weighing next to nothing, the tags are attached to the large mitten-shaped discal cell on the backside of a hind wing. Each tag has a unique set of letters and numbers. Monarch Watch recruits volunteers to tag monarchs, and over the years their volunteers have tagged about two million butterflies with some 20,000 recovered in Mexico.
The Xerces Society works to preserve invertebrates. Their Monarch Butterfly Conservation program focuses on conserving butterfly habitat and planting milkweed and nectar plants, as well as providing guidance and resources for anyone wanting to create pollinator habitat. Similarly, Monarch Watch encourages the planting of “waystations” for migrating monarchs; more than 40,000 are registered in North America. When creating a waystation by planting milkweed and nectar plants, species native to an area are best. Native plants adapted to a specific locale grow well and provide the host plants and high-quality nectar needed by the butterflies. In addition, a variety of native plants are needed so blooms are present from early spring through late fall for monarchs as well as a host of other pollinators.
Saving the migrating subspecies of monarch will require the cooperative work of all three countries, which is guided by the North American Monarch Conservation Plan, developed and issued in 2008 by the Commission for Environmental Cooperation. The 1994 North American Agreement on Environmental Cooperation between Canada, the U.S., and Mexico established the commission. The Monarch Conservation Plan’s main objectives are (1) decreasing or eliminating deforestation in the overwintering habitat; (2) addressing threats of habitat loss and degradation in the flyway; (3) addressing threats of loss, fragmentation, and modification of breeding habitat; (4) promoting sustainable livelihoods for the local population; and (5) monitoring monarchs throughout the flyway.
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