This issue briefing comes to us from Aaron Urquidez and Momi Jeschke, two of the four student researchers from Swarthmore, who spent 10 weeks with POP this spring researching and developing resources for our School Orchard Program on addressing threatened pollinator habitat.

Monarch butterflies (Danaus plexippus) are a long-migratory species of butterfly that span much of North America and use the milkweed (Asclepius spp.) as their mating habitat. Although not officially listed as threatened or endangered, monarch butterflies have experienced massive decline in their population. Since the 1980s there has been more than a 80% decrease in the eastern migration and about 99.4% decrease in their western migration. That is roughly a decrease from 4.5 million to approximately 28,000 today. Later this year the U.S. Fish and Wildlife Service was to have voted on whether the monarch butterfly should be protected under the Endangered Species Act; given recent moves to change the way this Act is applied, it is unclear that the monarch’s threatened habitats would be adequately protected to ensure the survival of the species.

 Each fall, monarchs make an epic flight from the northern plains of the U.S. and Canada to their overwintering grounds in the oyamel fir forests north of Mexico City that exist at elevations of 9,000 feet. Map credit: Xerces Society.

Each fall in late October, millions of monarchs head to southwestern Mexico City to hibernate in the high-elevation oyamel fir forests, where their return is culturally significant, viewed as the spirits of the deceased returning home for Dias de los Muertos. By February and March, the final generations of hibernating monarch butterflies come out of hibernation to find a mate. They then migrate north and east in order to lay their eggs on species of milkweed, which become generation one of the new year.

When focusing on conservation of the monarch population, it is important that all stages of the monarch’s life-cycle are supported, this support is maintained throughout its migration. Monarch butterflies go through four stages during one life cycle (the egg, the larvae (caterpillar), pupa (chrysalis), and the adult) and through four generations in one year.

The larvae hatch into baby caterpillars in 4 days, feeding on the nutrient rich layers of egg, and after two weeks of feeding on the milkweed, the larvae begin spinning their chrysalis and their 10-day process of metamorphosis, wherein they will emerge as an adult. Adults feed on nectar rich plants for 2-6 weeks and then die after laying eggs for generation two. The process continues through generations 2-3, until the fourth generation is hatched in September / October, which instead of dying after 2-6 weeks, migrates, hibernates, and begins the process again.

The root issue of monarch decline can be sited to loss of suitable habitat, whether this is the physical space, or the loss of their sustenance: milkweed, and nectar plants. Forests in North America have experienced mass amounts of logging and deforestation which has jeopardized much of the biodiversity on the continent.  The milkweed has been affected by the mass amounts of herbicides that are used to kill the competing plants of important crops in agricultural America as well as domestic use of RoundUp, a chemical compound used as weed killer. 

Monarchs perch on the trunks and branches of oyamel fir trees. Photo credit: Frans Lanting Mint Images from Sciance Magazine.

There is work to be done at many levels to help correct this issue, and restore monarch populations. The most immediate and effective course of action would be a restructuring at the governmental level to prioritize the issues of climate change (and all its connotations), biodiversity loss, and the threatening of species. Regulating deforestation and managing pesticide use would reduce the habitat loss of the monarchs. Climate change is threatening the oyamel firs, the very species monarch butterflies rely on for overwintering, as is competition for land by agricultural use. Some Mexican scientists, including plan architect Cuauhtémoc Sáenz-Romero from the Universidad Michoacana de San Nicolás de Hidalgo, are undertaking the work of assisted migration, planting oyamel seedlings in elevations suitable for their growth beginning at 11,268 feet where the habitat is projected to be suitable by 2030, outside the current range and protection area of the Monarch Butterfly Biosphere Reserve.

At the state government level, these regulations can be issued on a smaller scale. In addition, state government officials can advocate for habitat protection and restoration at the federal level. Landscape designers can design more sustainable buildings and complexes, and include space for natural monarch habitat to remain.

A monarch butterfly draws nectar from a species of swamp milkweed (Asclepias incarnata). Other rich sources of nectar for monarchs include zinnia flowers, Mexican sunflowers, Callistemon spp., and dwarf butterfly bushes. Photo credit: Xerces Society. 

The next solutions can be done at the organizational level. Groups situated in certain places can work to restore the milkweed plant, opting for natural pesticides and controls. These groups tend to focus on spreading awareness to the public, and these large organizations and movements can advocate for change at the state level. Organizations like Monarch Watch are working on the public education piece as a large scale citizen-science coalition of researchers, students, and advocates that’s been tagging monarchs since 1992 to help understand the dynamics of their fall migration. Originally initiated by Dr. Fred Urquhart of the University of Toronto, the organization continues to send out more than a quarter of a million tags to thousands of volunteers across North America which is compiled at the end of tagging season to be used in research.

The most important thing growers can do is reduce their use of pesticides. Highly susceptible to these pesticides, milkweed restoration will be more effective if the continued damage is abated. In addition to reduction of pesticides, growers can use sustainable machines and technologies, opting for renewable energy to lessen further impact on climate change.

Implementing solutions at the community level is vital for spreading awareness and restoring habitat and food for monarchs. Community gardens and orchards can be maintained, focusing on creating environments for monarchs, and using natural pesticides and controls. Community events focused on spreading the word and advocacy is also very important, as many people are unaware of what they can do to help. 

There are already many programs in place in Pennsylvania focusing on advocacy and awareness of the necessity of restoration. Programs such as the Xerces Foundation, which focuses on invertebrate conservation, use applied research, advocacy, education, and analyzing policy to work towards this restoration. Other programs such as the Pennsylvania State Environmental Group focus on informing the public about these species declines, and addresses solutions to climate change at many levels. The U.S. Fish and Wildlife Service promotes information on what rural and urban communities can do to help with monarch conservation. Monarch Watch, mentioned above, is updated routinely with information about the monarch decline, and provides free milkweed for habitat restoration projects along the Monarch Milkweed Corridor and to schools and educational non-profits.

The quick-list: 5 ways you can advocate for monarch butterflies! 

  • Connect with Xerces Foundation, which 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. 
  • At the state level, connect with Pennsylvania State Environment Group, which spreads awareness on the problems and solutions facing our state species.
  • At the community level, FWS provides information on what communities can do for monarch conservation.
  • Consider how to turn your landscape into a habitat-friendly space for monarchs!
    • Grow caterpillar plants: milkweed (100 types)
    • Grow nectar plants for adult monarchs:
      • Plants in the sunflower family, which includes asters, black-eyed susans, calendula, coreopsis, purple coneflowers and zinnias, are particularly nectar-rich
    • Pesticide control – use least toxic pesticides or natural controls (birds and special insects)
  • As many of the solutions to monarch decline coincide with general climate change, advocating for self-sustainability solutions to lessen impact can have benefit. Check out this list of 10 simple individual acts (that magnified) can have impact!

Sources (localized)

This POP Blog Post was written by 2019 Swarthmore student researchers Aaron Urquidez and Momi Jeschke, with support from Education Director Alyssa Schimmel.  

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