Firefly Light Dimmed Globally by Farmers, Builders, and Tourists, Study Reveals

Humans are at fault for the habitat loss, pesticide use and artificial light that threaten this popular insect population in Israel and around the world

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A firefly beetle.
A firefly beetle.

The light of firefly beetles is in danger of dimming, according to an extensive new survey published in the journal Bioscience. These insects, known for the bioluminescent glow their bodies emit during courtship, are vulnerable today to many dangers – particularly, destruction of their natural habitats, and exposure to pesticides, artificial light and tourists.

There are more than 2,000 species of firefly beetles, also known simply as fireflies or as lightning bugs, not all of which can fly. Eight are found in Israel, in a variety of habitats. The light they create is a result of a chemical process involving oxidation of a compound in their bodies called luciferin. 

The light of firefly beetles as seen on a tree in Thailand.Credit: AFP

A large team of researchers found that changes in habitat due to cultivation of crops – and concurrent use of insecticides – or due to construction constitute the main threat to fireflies. In many cases the vegetation on which the fireflies depend has been completely eradicated by construction. An example of this is the unusual environment in Saitama, Japan, north of Tokyo.

This region, where traditional agriculture was once practiced and where a large range of flora once thrived, has been neglected in recent years and has become unsuitable for some firefly species. In Malaysia, for example, one species disappeared completely after its riverbank mangrove habitat was destroyed to make way for agriculture. In forests along the Atlantic coast of Brazil, logging operations have severely compromised firefly-friendly environments.

Another serious danger to these insects is artificial light, both direct and also that emitted in a more diffuse way and affecting large areas. Such illumination confuses fireflies and disrupts their communication and ability to reproduce. Some species communicate by means of emitting flashes of light, and the new study cites a decline in this activity, particularly in natural areas that abut urban spaces.

The third major danger to the world firefly population is tourism. An estimated 200,000 people worldwide travel each year to sites known for their firefly activity – especially places where large numbers of them flash at virtually the same time, creating a very impressive visual effect.

The presence of tourists in some of these places, the researchers warn, could disrupt the creatures’ mating habits.

The firefly survey was headed by Sara M. Lewis of Tufts University and carried out by a group of scientists from the International Union for the Conservation of Nature, based on findings from dozens of experts around the globe. The scientists stress that the data are partial, and more research is needed to obtain a better picture of the plight of the world’s firefly population.

According to Ittai Renan, who teaches in Tel Aviv University’s zoology department and heads Israel’s National Ecosystem Assessment Program, the population of fireflies in Israel is also in decline. One of Renan’s students, Ella Fishman, has recently launched a study aimed at identifying the factors endangering the local species, and to that end is planning to enlist the public to report their observations.

Also involved in supervising the new research are Professors Tamar Dayan of TAU and Salit Kark, of the University of Queensland, Australia.

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