An Endangered Species Recovery Plan

SAVING THE
MONARCH
BUTTERFLY

By Jiulin Song

Introduction

What Is Biodiversity?

Biodiversity is the variety of life on Earth, encompassing the diversity of species, genes, and ecosystems, as well as the evolutionary, ecological, and cultural processes that sustain life.[1] It matters because it supports many of humanity's most basic needs, including food, water, shelter, and medicine. Biodiversity provides crucial ecosystem services such as pollination, seed dispersal, climate regulation, and water purification that are essential for the functioning of natural systems and human economies alike.

Furthermore, biodiversity contains potential benefits not yet discovered or fully understood. Many of the world's medicines were originally derived from wild species, and scientists estimate that millions of species remain undescribed, each potentially holding keys to future medical, agricultural, or industrial breakthroughs.[1] Protecting biodiversity is therefore not just an environmental concern but a matter of human survival and long-term prosperity. The loss of even a single species can trigger cascading effects throughout an ecosystem, disrupting food webs, reducing resilience to environmental change, and diminishing the natural heritage we leave to future generations.

Species Profile

About the Monarch

Danaus plexippus

233,394

Western population (2024)

96%

Decline from prior year

90%

Overall decline since 1990s

The monarch butterfly (Danaus plexippus) is one of the most recognizable insects in North America. Native to North and South America, monarchs are also found in other regions with suitable conditions, such as Australia and the Iberian Peninsula.[4] These butterflies depend on milkweed plants (Asclepias spp.) as the sole food source for their larvae, while adults feed on nectar from a wide variety of flowering plants.[5]

The migratory monarch butterfly was classified as endangered on the IUCN Red List on July 21, 2022, reflecting severe population declines across its range.[3] On December 12, 2024, the U.S. Fish and Wildlife Service proposed listing the monarch as threatened under the Endangered Species Act, with species-specific protections and flexibilities to encourage conservation.[6] In the 2024 Western Monarch Count, only approximately 9,119 butterflies were recorded, a staggering 96% decrease from the previous year's count of 233,394.[7] The eastern population, which overwinters in Mexico, occupied just 1.79 hectares in December 2024, significantly below healthy historical levels.[8]

Range & Environment

Geographic Range & Habitat

Monarchs in flight during their annual migration through Mexico

North American monarch butterflies are divided into two major populations separated by the Rocky Mountains.[9] The eastern population breeds across the Midwest and eastern United States during spring and summer, then undertakes one of the most remarkable migrations in the animal kingdom, traveling up to 3,000 miles south to overwinter in the oyamel fir forests of central Mexico's mountain regions.[9] The western population breeds west of the Rockies and overwinters primarily in eucalyptus, Monterey pine, and Monterey cypress groves along coastal California and northern Baja Mexico.[7]

Monarchs can travel between 50 and 100 miles per day during migration, and the entire journey can take up to two months to complete.[9] Their breeding habitats are diverse, including agricultural fields, pasture land, prairie remnants, urban and suburban residential areas, gardens, and roadsides. Anywhere milkweed and nectar plants are available.[5] The presence of native milkweed species is the single most critical factor determining whether an area can support breeding monarchs.

Monarch Migration Routes

Eastern Route Western Route Overwintering Site

Reproduction

Breeding Behaviors

Egg

3–4 days

Larva

9–14 days

Chrysalis

9–15 days

Adult

2–5 weeks*

*Breeding adults live 2–5 weeks; the migratory “super generation” lives 6–9 months

Monarch butterflies begin breeding in spring as they arrive at their summer breeding grounds. Females lay their eggs exclusively on milkweed plants, typically depositing a single egg on the underside of a leaf.[5] The monarch life cycle consists of four stages: egg, lasting 3 to 4 days; larva (caterpillar), which progresses through five instars over 9 to 14 days; chrysalis (pupa), lasting 9 to 15 days; and adult butterfly.[4]

During the breeding season, adult monarchs spend their 2 to 5 week lifespan mating and nectaring on flowers, with females constantly searching for milkweed upon which to lay eggs.[5] Multiple generations are produced each summer, with 3 to 5 generations typical in the eastern population. The final generation of the year, born in late summer, enters a state called reproductive diapause. They do not breed but instead focus on building fat reserves and migrating south to overwintering sites. This remarkable “super generation” can live 6 to 9 months, compared to the 2 to 5 weeks of breeding adults.[5] Among milkweed species, swamp milkweed (Asclepias incarnata) and common milkweed (A. syriaca) are the most preferred for egg-laying.[10]

Monarch mate selection follows a two-phase courtship: males patrol breeding areas and pursue females in an aerial chase, which may culminate in a midair takedown that brings both butterflies to the ground, where the male courts the female through antennal contact.[20]

Ecological Interactions

Predators, Prey & Competition

Prey

Milkweed plants (larvae), nectar from diverse flowering plants (adults). Monarchs are herbivorous at all life stages.

Predators

Black-backed orioles, black-headed grosbeaks, spiders, fire ants, paper wasps, and various invertebrates.

Parasites

OE protozoan, tachinid flies, parasitoid wasp Pteromalus cassotis (up to 200 eggs per chrysalis).

Monarch butterflies are herbivorous throughout their life cycle. As larvae, they feed exclusively on milkweed, and as adults, they consume nectar from a variety of flowering plants.[4] By feeding on milkweed, monarch caterpillars sequester cardenolide toxins that make them unpalatable to many predators. They advertise this chemical defense with their distinctive bright orange and black warning coloration.[11]

Despite this defense, monarchs face numerous natural enemies. Black-backed orioles and black-headed grosbeaks are major predators at Mexican overwintering sites, having evolved tolerance to the butterflies' toxins. Spiders and fire ants prey on monarch eggs and caterpillars, while various wasp species feed on both larvae and adults. Tachinid flies are among the most significant larval parasitoids. They lay their eggs on monarch caterpillars, and the fly larvae consume the host from within. The parasitic wasp Pteromalus cassotis targets monarch chrysalises, laying up to 200 eggs inside a single pupa.[11]

The protozoan parasite Ophryocystis elektroscirrha (OE) is an increasingly serious threat. OE infection rates in the eastern monarch population have risen from less than 1% in 1968 to approximately 10% today. Infected butterflies suffer reduced flight ability, shorter lifespans, and in severe cases, death upon emerging from the chrysalis.[12] Additionally, many invertebrates compete with monarch larvae for milkweed resources. A 2019 study identified 36 previously unreported arthropod predators of monarch eggs and neonate larvae, including ants, spiders, lacewings, and mantids that attack monarchs on milkweed plants.[13]

Critical Threats

Why Is the Monarch Endangered?

Habitat Loss

Climate Change

Pesticides

Illegal Logging

The monarch butterfly's dramatic population decline is driven by multiple interacting threats. The primary cause is the widespread loss of milkweed habitat, particularly across the agricultural Midwest.[6] Beginning in the late 1990s, the adoption of herbicide-tolerant genetically engineered crops led to massive increases in the application of broad-spectrum herbicides, particularly glyphosate (Roundup), which eliminated milkweed from millions of acres of farmland.[14] This single factor is estimated to have destroyed over one billion milkweed plants in the Midwest alone.

Climate change compounds the problem by altering weather patterns along migration routes, causing more frequent extreme temperature events at overwintering sites, and disrupting the seasonal timing that monarchs depend on for breeding and migration.[6] In 2002 and 2016, severe winter storms killed hundreds of millions of monarchs at Mexican overwintering sites. Illegal and legal logging in Mexico's oyamel fir forests has degraded critical overwintering habitat, reducing the forest canopy that protects monarch clusters from cold and precipitation.[3] Along the California coast, development and land-use changes have destroyed many of the tree groves that western monarchs depend on for overwintering.[7]

Pesticide exposure poses a growing threat to monarchs at all life stages. Broad-spectrum insecticides contaminate nectar and milkweed tissue, while herbicides directly eliminate the milkweed plants monarchs depend on for breeding.[2] The combined effect of these threats has pushed the monarch butterfly to the brink, with over 95% of the western population and approximately 80 to 90% of the eastern population lost since the 1980s and 1990s.[7][6]

Recovery Plan

Goals & Objectives

Our recovery plan establishes three primary objectives. First, we aim to restore and protect sufficient milkweed and nectar habitat across the monarch's breeding range to support a self-sustaining population. Specifically, this means working toward the establishment of at least 1.8 billion additional milkweed stems planted across the breeding range, based on USGS estimates of approximately 28.5 milkweed stems needed to produce each overwintering monarch.[15] Second, we will work to protect and restore overwintering habitat in both central Mexico and coastal California, ensuring these critical refugia remain intact and functional. Third, we aim to reduce pesticide exposure across monarch habitat through policy advocacy, farmer education, and the promotion of integrated pest management practices.

The monarch butterfly is critically important for several ecological and cultural reasons. As a pollinator, it contributes to the reproduction of wildflowers and agricultural crops across its extensive range.[4] The monarch serves as an indicator species, meaning its population health reflects the overall condition of grassland and pollinator ecosystems across North America. If monarchs are declining, it signals that the broader ecosystem of native plants, pollinators, and the services they provide is also in trouble. The species also holds immense cultural significance, particularly in Mexico where the annual migration is celebrated in connection with Día de los Muertos traditions. Furthermore, the monarch's epic multi-generational migration, spanning multiple countries, represents one of nature's most extraordinary phenomena, and its loss would diminish the natural heritage of an entire continent.[16]

1.8B

Milkweed stems needed across range

6+ ha

Eastern overwintering area target

30K+

Minimum viable western population

Action Plan

Solutions

Our recovery plan takes a multi-pronged approach to address the full spectrum of threats facing the monarch butterfly, while carefully accounting for the species' unique habitat requirements, breeding patterns, and ecological relationships.

Habitat Restoration & Protection

The cornerstone of our plan is the restoration of milkweed habitat at scale. We will partner with agricultural producers through the USDA Natural Resources Conservation Service (NRCS) Farm Bill programs to plant native milkweed and nectar-producing plants along field borders, in buffers along waterways, around wetlands, and in pastures.[17] Milkweed will be planted in patches of 3 to 4 plants, with 10 to 13 patches per acre, to achieve optimal density for egg-laying females.[5] Only regionally appropriate native milkweed species will be used: common milkweed (A. syriaca) and swamp milkweed (A. incarnata) in the Midwest, and showy milkweed (A. speciosa) in the West. This supports both larval development and adult nectaring through the full breeding season. This approach directly addresses the monarch's breeding needs by providing the specific host plants that females require for egg-laying and that larvae need to complete their development.

Monarchs clustering on oyamel fir trees at an overwintering site in Michoacán, Mexico

Overwintering Site Protection

In Mexico, we will support ongoing efforts to prevent illegal logging in the Monarch Butterfly Biosphere Reserve and work with local communities to develop sustainable ecotourism alternatives that provide economic incentives for forest conservation. In California, we will advocate for the protection and restoration of overwintering groves, including planting wind-break trees and maintaining the microclimate conditions that monarchs require: cool temperatures, high humidity, and filtered sunlight.[7] This directly accounts for the monarch's behavioral need for sheltered, thermally stable overwintering habitat where they can cluster in large aggregations to conserve energy during the non-breeding months.

Pesticide Reduction

We will promote the adoption of integrated pest management (IPM) practices that reduce reliance on broad-spectrum herbicides and neonicotinoid insecticides in monarch habitat. This includes supporting organic and low-input farming practices in key breeding areas and advocating for pesticide buffer zones around known milkweed patches and migration corridors. Reducing pesticide exposure protects not only adult monarchs but also the milkweed plants they depend on for breeding, ensuring that restored habitat remains viable for egg-laying and larval development.[2]

Urban & Community Engagement

Through programs like the National Wildlife Federation's Mayors' Monarch Pledge, we will engage cities and communities across the migration route to create pollinator-friendly habitat in parks, gardens, roadsides, and other public spaces. As of 2025, over 2,300 mayors and local government leaders have committed to creating monarch habitat through this program.[16] Urban milkweed gardens provide essential stepping stones for migrating monarchs and supplemental breeding habitat that accounts for the species' increasingly suburban range.

Disease Management

Rather than pursuing captive breeding, which conservation experts have cautioned against due to risks of disease amplification and genetic issues,[18] we will focus on maintaining healthy wild populations by ensuring adequate milkweed availability. Sufficient milkweed reduces larval crowding, which is associated with higher OE parasite transmission rates. This approach respects the monarch's natural breeding behaviors and predator-prey dynamics while minimizing the spread of parasites that thrive in captive or overcrowded conditions.

Implementation Schedule

Timeline

Year 1 | 2026

Establish partnerships with NRCS, state wildlife agencies, and agricultural producers. Begin native milkweed seed collection from regional sources. Identify and prioritize 500,000 acres of restoration sites along key migration corridors. Deploy initial monitoring protocols and baseline surveys.

Years 2–3 | 2027–2028

Begin large-scale milkweed planting across the first 500,000 acres. Establish baseline population monitoring at all major overwintering sites. Launch community engagement through the Mayors' Monarch Pledge in 200 additional cities. Begin working with Mexican and California authorities on overwintering site protections.

Years 3–5 | 2028–2030

Expand habitat restoration to reach 2 million cumulative acres. Evaluate restoration effectiveness and adapt milkweed planting strategies based on egg-laying and larval survival data. Implement pesticide reduction programs in priority breeding areas.

Years 5–10 | 2030–2035

Scale to the full 6 million acre restoration target. Achieve interim population benchmarks of at least 30,000 butterflies for the western population and 4+ hectares of overwintering area for the eastern population. Continue adaptive management based on ongoing monitoring data.

We have selected a 10-year implementation timeline because monarch population recovery depends on restoring milkweed at a continental scale, which requires multi-year plant establishment periods and the coordination of hundreds of partners across three nations. Shorter timelines are unrealistic given the scale of habitat loss, while longer timelines risk allowing populations to decline below viable thresholds.[15]

Budget & Resources

Funding

We estimate a total 10-year program cost of approximately $200 million, drawing on the precedent set by the National Fish and Wildlife Foundation's Monarch Butterfly and Pollinators Conservation Fund, which has leveraged $82.3 million in conservation impact since 2015, including $31.7 million in direct grants and $50.6 million in grantee matching funds.[19] Funding will be sourced from a combination of NFWF competitive grants, USDA NRCS Farm Bill conservation programs, state wildlife agency contributions, U.S. Fish & Wildlife Service Endangered Species Act funding, private foundation grants, and public donations through established conservation organizations.[17][19]

Resource	Annual Cost	10-Year Total
Ecologists, field biologists & program staff	$2,000,000	$20,000,000
Native milkweed seed & seedling production	$5,000,000	$50,000,000
Land restoration equipment & supplies	$3,000,000	$30,000,000
Monitoring technology (GPS, weather stations, survey equipment)	$1,000,000	$10,000,000
Education, outreach & community engagement	$500,000	$5,000,000
Partnership coordination & administration	$500,000	$5,000,000
Vehicles & transportation	$1,000,000	$10,000,000
Land leases & conservation easements	$5,000,000	$50,000,000
Research, data analysis & adaptive management	$2,000,000	$20,000,000
Total	$20,000,000	$200,000,000

Milkweed & Seedlings 25%

Land Leases & Easements 25%

Restoration Equipment 15%

Staff & Research 20%

Operations, Education & Monitoring 15%

Evaluation

Measuring Success

Measuring the success of this recovery plan is arguably the most important component, ensuring that investments are yielding meaningful conservation outcomes and informing adaptive management decisions throughout the program's duration.

Population Monitoring

The primary measure of success will be annual monarch population counts at overwintering sites. For the eastern population, we will track the area (in hectares) occupied by monarch clusters in Mexico's Monarch Butterfly Biosphere Reserve, measured each December through trained biologist surveys. Our target is to increase from the current 1.79 hectares to at least 6 hectares within 10 years. For the western population, we will participate in and support the annual Western Monarch Count conducted each Thanksgiving by the Xerces Society, with a target of recovering to at least 30,000 butterflies, a threshold that population viability research has identified as critical for the long-term survival of the western migration.[7]

Habitat Metrics

Every spring and summer, field teams will conduct milkweed stem density surveys across restored habitat sites, measuring the number of milkweed plants per acre. Success targets include achieving at least 500 milkweed stems per acre in restored areas, based on research indicating that approximately 28.5 milkweed stems are needed to produce a single overwintering monarch.[15] Egg and larva counts will be conducted every two weeks during the breeding season (May through August) on randomly selected milkweed plants across monitoring sites to assess reproductive success and identify areas where additional habitat improvement is needed.

Health Indicators

We will monitor Ophryocystis elektroscirrha (OE) parasite infection rates through annual sampling of adult monarchs captured at both breeding and overwintering sites. Success means maintaining or reducing infection rates below 10%. Migration timing and route data will be collected through citizen science programs including Monarch Watch tagging and Journey North observations, providing continent-wide data on migration health.[5]

Reporting & Data Collection

Comprehensive data reports will be published annually, with interim assessments every three years to evaluate progress against milestones and adjust strategies as needed. All data will be shared publicly through the Monarch Joint Venture's data portal to support collaborative analysis and transparency. Field surveys will be conducted every two weeks during the breeding season (May–August) at established monitoring sites across the Midwest, Texas, and California. Overwintering counts will occur annually in December (Mexico) and at Thanksgiving (California). Habitat acreage will be tracked quarterly through GIS mapping and field verification.[5][8]

30,000+

Western population target