Monarch Migration Persists in New York City as Urban Plantings Provide Critical Habitat

Monarch butterflies, a species recently proposed for protection under the Endangered Species Act, are nonetheless visible and breeding across pockets of New York City, researchers, gardeners and park officials said. Small strips of native milkweed and pesticide-free wildflowers in community gardens, parks and even private yards are supporting eggs, caterpillars and adult monarchs during summer and early fall — the staging ground for the species’ long southbound migration.

The presence of monarchs in dense urban settings stands in contrast to large-scale declines seen across much of the species’ range. Federal and academic monitoring show monarchs that overwinter in the fir forests of central Mexico occupied an average of about 21 acres in the 1990s; that number fell to roughly 4.4 acres last winter. Scientists attribute most of that decline to the loss of milkweed, the only plant monarch caterpillars eat, largely eliminated in the Midwest by herbicide use and the conversion of grasslands to intensive row-crop agriculture.

Monarchs migrate up to about 2,000 miles from breeding areas in the eastern United States to overwintering groves in Mexico. Their multigenerational return north in spring and summer makes them especially vulnerable to losses of habitat along broad swathes of their route, experts say. "The average insect spends three-quarters of its life as a larva or an egg," said David Lohman, an insect ecologist at the City University of New York. "The whole habitat for that part of the life for most insects, including monarchs, is a single plant."

In New York, that single plant is often common or swamp milkweed, planted alongside native nectar sources such as bee balm, coneflowers and ironweed. Horticulturists and volunteers across multiple boroughs described a shift in plantings over the past decade: native perennials are becoming more common in public and private landscapes, and managers are tolerating a less manicured aesthetic in exchange for greater ecological value.

Brooklyn Bridge Park, built on former shipping piers, added native meadows and milkweed beds when it opened in 2010 and continues to select planting schemes with insects in mind, officials said. Small community green spaces and gardens, from a four-foot-wide strip in a Windsor Terrace community garden to a converted prairie at the Naval Cemetery Landscape in northern Brooklyn, are likewise supporting monarch life stages as well as other pollinators and birds.

Municipal efforts include propagation at a Department of Parks and Recreation native plant nursery in Staten Island, where staff grow species selected for their ecological benefits. Staffers and volunteers described removing invasive ornamentals and replacing them with native species that support pollinators, and in some cases leaving twigs, seed heads and leaf litter that provide nesting and overwintering habitat for insects.

Individuals and informal actors are also contributing. Some gardeners engage in so-called guerrilla planting, placing milkweed and other natives in tree pits or underused park edges. Park officials said those efforts are often well-intentioned but sometimes raise concerns about sight lines or suitability of particular species for a site. Other residents have turned front yards into mini-prairies, documenting leaf-cutter bee nests, cicada-killer wasps and a range of beetles and flies that a more conventional landscape would not support.

A number of conservation groups run volunteer activities that connect city residents with monarch monitoring and management. Monarch Watch, an educational program and research network, coordinates a tagging effort each fall in which volunteers affix tiny numbered stickers to monarch wings to help researchers track migration origins and survival. The program depends on volunteers finding, catching or raising butterflies, and the data collected helps scientists better understand movement patterns and mortality on the migration route.

Even small, distributed actions can make a measurable difference, ecologists said. Because monarch caterpillars feed on a single plant genus, increasing the abundance of milkweed in urban settings directly increases the number of potential larval sites. Native nectar flowers, planted without pesticides, supply adult butterflies with fuel to continue migration.

Researchers caution that cities alone cannot halt monarch declines. The loss of milkweed and nectar plants across agricultural landscapes remains the major driver of long-term population trends, and migratory monarchs face hazards including storms, road mortality and pesticide exposure along the entire route to Mexico. Still, urban habitats can serve as complementary refuges and as sites for public engagement and education that can translate into broader conservation action.

Conservationists and park managers framed the local work as both practical and symbolic: practical in that it provides immediate resources for monarchs and other wildlife, and symbolic in how it enables residents to observe and participate in conservation. Visitors to city meadows and community gardens often report emotional and mental-health benefits from time spent in those green spaces, and educators say monarchs, because of their visibility and migratory story, are effective ambassadors for broader biodiversity issues.

The city-based activity comes as federal officials weigh stronger protections. The Biden administration last year proposed listing the monarch under the Endangered Species Act, a step that, if finalized, could trigger additional conservation measures on private and public lands across the species’ range.

Local practitioners emphasized that planting native milkweed and nectar sources is a tangible action residents can take. "Every little bit counts," said one volunteer gardener involved in planting and outreach work. Municipal programs, nonprofit initiatives and individual gardens together create a patchwork of habitat that, while not a substitute for large-scale landscape restoration, helps sustain monarchs through parts of their life cycle and keeps the fall migration a visible phenomenon even in dense urban centers.

City officials, horticulturists and volunteers said that the lesson from New York’s experience is straightforward: restoring native plants in small, distributed sites can provide direct ecological benefits and foster public support for larger conservation efforts. That combination, they said, is one practical way to help a migratory species whose long-distance survival depends on habitat distributed across an entire continent.