An Endangered Species Recovery Plan

SAVING THE
MONARCH
BUTTERFLY

By Jiulin Song

Introduction

What Is Biodiversity?

Monarch butterfly on purple coneflower in Michigan

Tallgrass prairie wildflowers at Glacial Ridge National Wildlife Refuge

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.[1]

Biodiversity also preserves options we do not fully understand yet. Many medicines have roots in nature, and species that have not been fully studied may still hold future medical or agricultural value.[1] Protecting biodiversity is not only an environmental goal. It also helps keep ecosystems resilient as conditions change and reduces the risk of wider disruptions across food webs. [1]

Species Profile

About the Monarch

Danaus plexippus

Male monarch butterfly with wings spread

233,394

Western count (2024-25)

96%

Drop in 2024-25 count

90%

Long-term decline

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.[2] 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.[3]

The migratory monarch butterfly was classified as endangered on the IUCN Red List on July 21, 2022, reflecting severe population declines across its range.[4] 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.[5] The 2024 Western Monarch Count recorded 9,119 butterflies, down 96% from the 2023 peak of 233,394.[6] The eastern population, which overwinters in Mexico, occupied just 1.79 hectares in December 2024, still well below the long-term average.[7]

Range & Environment

Geographic Range & Habitat

Monarch butterflies in flight during migration in Mexico

Monarchs in flight during their annual migration through Mexico

North American monarch butterflies are divided into two major populations separated by the Rocky Mountains.[8] 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.[8] 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.[6]

Monarchs can travel between 50 and 100 miles per day during migration, and the entire journey can take up to two months to complete.[8] 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.[3] 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

Monarch caterpillar with yellow and black stripes

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.[3] 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.[2]

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.[3] 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.[3] Among milkweed species, swamp milkweed (Asclepias incarnata) and common milkweed (A. syriaca) are the most preferred for egg-laying.[9]

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.[10]

Ecological Interactions

Predators, Prey & Competition

Common milkweed stand that supports monarch larvae and nectar resources

Prey

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

Black-headed grosbeak, a monarch butterfly predator

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.[2] 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] The oleander aphid (Aphis nerii) is among the most consequential milkweed competitors: infested plants receive over three times fewer monarch eggs, and larvae that feed on aphid-infested milkweed experience 22% mortality and reach less than half the final body weight of larvae on aphid-free plants.[14]

Critical Threats

Why Is the Monarch Endangered?

Herbicide spraying in agricultural habitat where native milkweed is removed

Habitat Loss

Monarch butterflies killed by winter storms at Mexican overwintering site

Climate Change

Large-scale soybean monoculture associated with herbicide-intensive management

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.[5] 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.[15] USGS and partner estimates cited in federal recovery planning show that restoring the species will require roughly 1.8 billion additional stems to offset those losses.[16]

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.[5] Severe winter storms have repeatedly caused major mortality events at Mexican overwintering sites. Forest degradation in Mexico's oyamel fir region further reduces the canopy cover that protects clustered butterflies from cold and precipitation.[4] Along the California coast, development and land-use changes have destroyed many of the tree groves that western monarchs depend on for overwintering.[6]

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.[17] Together, these pressures have driven steep declines in both migratory populations, leaving the western population at near-record lows and the eastern population far below recovery targets.[6][5][16]

Eastern Overwintering Area (1994–2024)

Source: WWF-CONANP monarch monitoring data[7]

Primary Threats

Based on USFWS listing assessment[5] and IUCN review[4]

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.[16] 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.[5]

The monarch matters beyond its own survival. It is part of broader pollinator systems, serves as a visible indicator of habitat quality, and carries cultural significance across North America, especially because of its multi-generational migration and its place in community conservation efforts.[1][18] Monarchs also hold significant scientific value: research into their self-medication behavior has shown that infected females preferentially lay eggs on milkweed species with higher concentrations of cardenolides (cardiac glycoside compounds), which suppress Ophryocystis elektroscirrha spore production and extend monarch lifespan. This finding has broader implications for understanding parasite-host coevolution and medication-like behavior in insects.[19]

1.8B

Milkweed stems needed across range

6+ ha

Eastern overwintering area target

30K+

Near-term western milestone

Habitat Restoration Targets

Action Plan

Solutions

Native prairie restoration with diverse wildflowers and grasses

Soybean monoculture with limited milkweed habitat

Before After

Before: soybean monoculture to after: native prairie restoration for pollinator corridorsWikimedia Commons

Our recovery plan focuses on the major pressure points identified across the listed sources: habitat loss, overwintering site degradation, pesticide exposure, and avoidable disease risk. The goal is to rebuild habitat at scale while protecting the places monarchs already rely on.[5][20]

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.[21] We will prioritize regionally appropriate native milkweeds and companion nectar plants, because females lay eggs on milkweed and larvae cannot develop without it.[3] USDA guidance and monarch habitat research both support diverse, locally suited plantings rather than one-size-fits-all mixes.[9]

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.[8] This directly protects the sheltered, thermally stable conditions monarchs need while overwintering in dense clusters.[6]

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, helping restored habitat remain usable for egg-laying and larval development.[17]

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. By 2025, roughly 2,000 mayors and local government leaders had committed to creating monarch habitat through this program.[18] Urban milkweed gardens can provide stepping-stone habitat for migrants and supplemental breeding habitat where suitable native plants are available.[3]

Disease Management

Rather than pursuing captive breeding, which conservation experts have cautioned against due to risks of disease amplification and genetic issues,[20] we will focus on maintaining healthy wild populations through habitat quality, lower crowding, and better public guidance on handling and rearing. That keeps the emphasis on wild migration and reduces conditions that can worsen parasite spread.[12]

Native prairie restoration with diverse flowering plants

Monarch butterflies in flight at overwintering region

Cover crops supporting soil health and reducing herbicide reliance

Community pollinator garden at Meadowood with native flowering plants

Restored native prairie with diverse flowering plants and grasses.Wikimedia Commons

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.

A 10-year timeline is more realistic than a short campaign because monarch recovery depends on habitat establishment at continental scale, repeated monitoring, and coordination across many agencies, landowners, and communities. The timeline is long enough for restoration to take hold, but short enough to keep the plan accountable to measurable benchmarks.[16]

Budget & Resources

Funding

We frame this as a planning-scale 10-year budget of about $200 million. That figure is a proposed implementation estimate, not a published federal budget line. For context, the National Fish and Wildlife Foundation's Monarch Butterfly and Pollinators Conservation Fund 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.[22] Funding would likely combine NFWF competitive grants, USDA NRCS Farm Bill conservation programs, state wildlife agency contributions, U.S. Fish & Wildlife Service support, private foundation grants, and public donations through established conservation organizations.[21][22]

Volunteers planting native species at a habitat restoration site

Restoration planting at a dam removal site with 4,000+ plants of 24 native speciesUSFWS

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

Budget Allocation

Milkweed & Seedlings 25%

Land Leases & Easements 25%

Restoration Equipment 15%

Staff & Research 20%

Operations, Education & Monitoring 15%

Evaluation

Measuring Success

Success has to be measured in a way that matches the monarch's real life cycle and migration pattern. That means tracking population size, habitat quality, and disease pressure over multiple seasons, then adjusting the plan as results come in.

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 each winter. 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 use the annual Western Monarch Count as the clearest shared benchmark and aim to recover well above the most recent 9,119 count, with 30,000 as a practical near-term milestone.[6][7]

Habitat Metrics

Every spring and summer, field teams will track milkweed establishment, nectar plant cover, and monarch use of restored sites. The point is not only to plant acreage, but to confirm that habitat is producing eggs, larvae, and adults over time. Those field checks can then be compared with the broader USGS stem targets that underpin the recovery strategy.[16]

Health Indicators

We will monitor Ophryocystis elektroscirrha (OE) parasite infection rates through periodic sampling of adult monarchs at breeding and overwintering sites. Success means keeping infection rates from rising while improving survival and migration performance. Migration timing and route data from established citizen-science efforts can help show whether habitat improvements are translating into healthier movement across the flyway.[12][3]

Reporting & Data Collection

Results should be reviewed every year and compared against the same core measures each time: eastern overwintering area, western count totals, habitat establishment, and observed breeding activity. That keeps the plan transparent and makes it easier to adjust quickly if one strategy is not delivering the expected gains.[7]

30,000+

Western population target