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Firefly Threats and Conservation Efforts

A mountainous scene is shown at night, with a small, glowing city in the lower right-hand corner. The mountains are dwarfed by an enormous sky, peppered with patchy clouds and swaths of stars. The sky has an unnatural glow (literally), with fields of yellow-green and orangish light, indicating light pollution.
Light pollution comes in several forms, including skyglow (pictured). (Photo: Mike Lewinski / Flickr Creative Commons 2.0)

Anecdotal reports from around the world tell of firefly declines. While the extent of declines and their causes are not yet well-understood, we do have a basic understanding of major threats to fireflies—including habitat degradation and loss, light pollution, pesticide use, poor water quality, climate change, invasive species, and over-collection.

Fireflies may be most vulnerable during their larval stage, which can last up to two years. Adults, on the other hand, are generally active for only a few weeks each year. Species with specific habitat requirements or narrow or patchy distributions are often more at risk, and certain life history traits can increase vulnerability. Threats to soft-bodied invertebrates such as earthworms, snails, and slugs—larval fireflies’ preferred food sources--may have cascading effects on firefly populations.

Regardless of the specific reasons for their decline, researchers agree that protecting, restoring, and enhancing firefly habitat is one of the best ways to conserve their populations. In addition, collecting baseline data on firefly populations and distributions will contribute to a better understanding of their conservation status.

 

Our Strategy

Xerces has adopted several key strategies to conserve fireflies. These include compiling a species occurrence database for the United States and Canada; compiling a life history matrix to identify key traits that may influence each species’ vulnerability to extinction; evaluating the conservation status and extinction risk of firefly species in the United States and Canada; identifying firefly hot spots; and developing and publishing conservation guidelines. Education and outreach are also key components of our firefly conservation work, including webinars and training workshops for land managers and community scientists, outreach to engage people in community science programs such as Firefly Watch, and producing science-based documents to outline the needs of fireflies and recommend ways that individuals can help. Everyone can play a role in firefly conservation—from providing habitat to mitigating light pollution, curbing pesticide use, and sharing firefly observations through community science initiatives.

 

Main Threats to Fireflies

Habitat Degradation and Loss

Commercial and residential development, water pollution, and groundwater pumping are some of the key drivers of firefly habitat loss and degradation.

(Photo: Xerces Society / Emily May)

Light Pollution

Light pollution comes in several forms, including skyglow (glowing haze over highly populated areas), light trespass (light that reaches beyond intended or needed area), and glare (light that excessively illuminates areas or objects).

(NASA Earth Observatory image by Robert Simmon; Suomi NPP VIIRS data courtesy of Chris Elvidge, NOAA National Geophysical Data Center)

Pesticide Use

Fireflies can be exposed to pesticides in a variety of ways—via direct applications to their habitat, runoff from agricultural or ornamental applications, or consumption of contaminated prey. Their reliance on moist habitats means they are vulnerable to pesticides moving through water.

(Photo: Radim Schreiber, fireflyexperience.org)

Habitat Degradation and Loss

Most firefly species—and their prey—depend on moist habitats, including wetlands, streams, and damp fields. Modification of aquatic habitats, such as dams and channelized irrigation ditches, can negatively affect firefly populations. Drought, disruption of natural water flows, and diminishing water tables may be issues for species in arid areas of the West. In more urbanized areas, residential development and loss of leaf-litter habitat required during larval life stages is also a concern. Habitat loss can be especially detrimental for species with flightless females, as these females cannot disperse far beyond their natal sites. Flightless females and larvae are also at higher risk of physical crushing.


Light Pollution

Light pollution can be caused by street and house lights, vehicle headlights, billboards, and even gas flares from oil fields. All sources of artificial light at night, or ALAN for short, have the potential to drive declines in firefly populations. Unfortunately for fireflies and other affected species, including humans, night sky brightness worldwide is only continuing to increase in both intensity and extent. More than three-quarters of firefly species in the United States and Canada are nocturnal or crepuscular (active at dusk), and these species use light of their own making to communicate. Researchers have speculated that artificial light from street lamps, residences, and other sources may obscure natural firefly bioluminescence, with potentially catastrophic outcomes for species that depend on these signals to find mates or ward off predators, and a growing body of research supports this assertion.

 

Pesticide Use

While there is very little research on the direct effects of pesticides on fireflies, their vulnerability can be assessed from research on similar species and firefly prey, as well as observations from firefly researchers. Since most species spend the majority of their lives as larvae consuming earthworms, slugs, and snails, pesticide impacts on these food sources are likely to have negative consequences for fireflies. Herbicides also have the potential to indirectly affect firefly populations by eliminating vegetation needed for shelter, forage, overwintering, and mating. Larvae and flightless adult females are likely the most vulnerable to pesticides because they are relatively immobile and unable to disperse away from treated sites. Learn more about reducing pesticide impacts in aquatic ecosystems here.

 

Conservation Efforts

Compiling a Species Occurrence Database & Life History Database 

This will serve to address gaps in knowledge and identify key traits that may influence firefly species’ vulnerability to extinction. As part of this approach, we are identifying key habitat types that may be essential to fireflies.

(Photo: Katja Schulz / Flickr Creative Commons 2.0)

Evaluating the Conservation Status & Extinction Risk for Species in the United States and Canada

We will also communicate the results of these findings to state wildlife agencies so that conservation efforts can be directed toward the most appropriate species.

Pursuing Endangered Species Act Protections for Imperiled Species

such as the Bethany Beach firefly, which is known from only a few sites along the Atlantic Coast in Delaware. Residential development and rising tides due to climate change threaten this species.

(Photo: Christopher Heckscher)

Identifying Firefly Hotspots

so these can be prioritized for conservation based on occurrence of rare species and areas of high firefly diversity.

(Photo: Radim Schreiber, fireflyexperience.org)

Protecting & Restoring Known Firefly Habitats

This will help to ensure these sites and their resident fireflies persist.

(Photo: Xerces Society / Emily May)

Raising Awareness of Fireflies & Their Conservation Needs

and providing educational materials such as firefly conservation guidelines that can be used by the public and land managers.

(Photo: Radim Schreiber, fireflyexperience.org)

Learn More