Fireflies are dimming locally, but you can help keep the spark alive

NORTH SHORE — On warm summer evenings across the North Shore, twilight used to bring a familiar, spellbinding display: dozens of tiny yellow-green lights flickering across backyards, marshes, and forest edges.

However, residents throughout Massachusetts may notice these summer visitors are getting harder to spot. Documented population declines are threatening fireflies across the region, driven by habitat loss, light pollution, pesticide use, and climate change.

While generalist species like the common eastern firefly still flash in dark, damp habitats, populations across North America face severe pressure. Experts report that 18 firefly species in the United States now face extinction.

Scientists and wildlife officials point to several overlapping environmental pressures causing the decline. Chief among them is artificial outdoor lighting from streetlights, security systems, and commercial buildings, which disrupts the flash-based mating rituals fireflies rely on. Male fireflies flash specific color and timing patterns to signal females on the ground, but artificial light outshines these cues.

At the same time, urban development and modern lawn maintenance — specifically the removal of leaf litter and tall grass — destroy crucial breeding grounds.

Fireflies spend up to two years maturing underground or in moist soil as larvae, feeding on earthworms, snails, and slugs. Chemical sprays for mosquito control and lawn care further compound the issue by killing adult fireflies, disrupting larval metabolism, and eliminating their primary food sources. Environmental stress from drought and rising sea levels associated with climate change adds even more pressure to these vulnerable habitats.

Despite these challenges, conservation experts emphasize that landowners can take simple, immediate steps in their own backyards to help protect local populations. Extinguishing porch lamps at night, installing motion sensors, and pulling window blinds shut prevent light leakage from interfering with mating signals. Leaving fallen leaves along the edges of a property in autumn provides essential, moist microhabitats where firefly larvae can feed and develop over the winter.

Adjusting routine lawn care can also make a significant difference. Allowing grass to grow to about 4 inches, mowing less frequently, and planting native trees and shrubs helps retain soil moisture.

Homeowners can also opt for non-chemical solutions for lawn care to avoid harming beneficial species. When visiting public firefly viewing areas, staying on designated paths protects fragile larvae in the soil from being crushed.

Protecting fireflies does more than preserve a beloved tradition — it safeguards the broader ecosystem. Insects form the foundation of the local food web, supporting birds, amphibians, and other wildlife. By making small adjustments to outdoor spaces, North Shore neighbors can help ensure future generations continue to enjoy the summer light show.