On summer evenings in Brooklyn, a rare natural spectacle is unfolding amid the urban landscape: fireflies have been lighting up the dusk around the Greenway Botanical Garden at the Naval Cemetery, a nearly two-acre green space nestled between the Brooklyn-Queens Expressway and the Brooklyn Navy Yard. The garden, part of the Brooklyn Greenway Initiative’s project to create a scenic waterfront path for pedestrians and cyclists, includes native tall grasses, wildflower meadows, and a wooden plank walkway encircling grounds that still hold approximately 500 19th-century military burials.

Avvah Rossi, director of horticulture for the initiative, observed a notable increase in firefly activity over the past three years, attributing the summer emergence to carefully maintained native vegetation and organic soil management. Fireflies, which spend the majority of their two-year life cycle as larvae underground, depend on healthy soil ecosystems rich in invertebrate prey such as slugs. As adults, they have a brief lifespan during which their primary focus is mating, often signaled through their characteristic bioluminescent flashes.

While anecdotal reports suggest firefly sightings in New York City have become more common, there is no comprehensive data confirming an increase in their numbers. Richard Joyce, a conservation biologist with the Xerces Society, a nonprofit dedicated to insect conservation, explained that historical habitat conditions may have made fireflies so commonplace that their presence went largely unnoticed in earlier decades. Recent urban and climate changes have complicated this picture.

Jessica Ware, head of the invertebrate zoology division at the American Museum of Natural History, noted that fireflies thrive in warm, moist conditions, which have recently become more frequent with New York City’s emerging subtropical climate classification. Wet springs provide ideal conditions for larval feeding and development. However, she cautioned that extreme temperature fluctuations, including heat and drought, threaten firefly populations by disrupting their food sources and breeding habitats.

Among roughly 40 species recorded in New York State, the most often seen in urban areas is the Big Dipper, or Photinus pyralis, also known as the common eastern firefly. This species is notably resilient and adaptable, capable of thriving amid city lights and noise. Its range extends from northern Mexico through major U.S. cities like Dallas and Atlanta, underscoring its tolerance to human-altered environments. Big Dippers emit their flashes around sunset to attract mates and can tolerate some level of ambient light, unlike many firefly species requiring complete darkness.

Firefly populations face threats from habitat loss and environmental change, with at least 18 of the 132 North American firefly species assessed being considered at risk, particularly those inhabiting vulnerable salt marshes in the Northeast and mid-Atlantic regions.

In the Bronx, the New York Botanical Garden has documented at least four firefly species since 2009, noting that non-glowing species disappear by late spring, while glowing fireflies fade by mid-August. Given their brief adult phase, lasting only a few weeks, the opportunity for New Yorkers to witness these bioluminescent insects occurs primarily in the summer months, within green spaces across the city.

Experts encourage residents to seek out fireflies during the dusk hours and appreciate their fleeting presence. According to Joyce, fireflies offer a rare and serene connection to nature, capable of uplifting moods and emotions amid the city's bustle.