Right in Our Backyard

Fireflies and Climate Change

By Bill Lawyer

Ever since I started writing articles about nature and the environment, I’ve been getting questions about the fate of fireflies, vis-à-vis global climate change.

Fireflies (which are actually a type of beetle) have always symbolized to me the delicate beauty and amazing variety of the wildlife that we have all around us.

Yes, you can go to a place like Thailand or Bioluminescent Bay in Puerto Rico and see spectacular clusters of fireflies, but for many years all I had to do was go to one of the fields or meadows nearby (including my backyard).

I still see an occasional firefly, and enjoy watching neighborhood children trying to capture some for a close look (before returning them).

Inside their small bodies, fireflies have developed the chemical and biological attributes to produce light without producing heat.

Ironically, while scientists have come up with many ways to use their knowledge of bioluminescence, we keep destroying the open spaces that fireflies need to carry out their courtship and procreation rituals.

According to a recent issue of Science Magazine, scientists from universities in Michigan have been carrying on a survey of the firefly population for the past dozen years. During that time, they found that the population varies on a three-year cycle — increasing or decreasing. While they don’t have conclusive proof as to why this is happening, so far they’ve posited that fireflies need warm weather to function, but also sufficient rainfall.

Cornell University scientists have noted that as average temperatures rise, fireflies emerge earlier which may impact on the foods they eat (or what eats them).

Entomology Professor Michael Hoffman says that one possible reason for the seeming increase in numbers of fireflies in Michigan may be caused by wet springs, a trend that will occur with climate change in the Northeastern U.S.

Since we have just experienced a relatively wet spring and early summer, firefly populations in Rye should be growing. That’s because firefly larvae (glow worms) feed on snails, slugs, and other small invertebrates. With more moisture, the number of snails and slugs likely increase, providing more food for fireflies and insuring good populations of adults.

But many of the wetlands and meadows that would normally be providing those moist conditions are drying up or being paved over.

Other factors to consider here in Rye are the use of insecticides, and the conversion of streams into storm sewers. Increased artificial lighting has had an impact as well, making it harder for fireflies to find potential mates.

Overall, it seems as though there is no simple answer to the question of changing population numbers. Dr. Hoffman says that continued research is required, along with expanded coverage of firefly populations in other parts of the country.

My most recent close encounter with a firefly was when I was taking my dog out for a walk, and I found one on my kitchen counter. I have no idea how it got there. Luckily, I was able to get it out the door and it flew away.

As I’m writing this, at about 8:30 in the evening, I can see a couple of fireflies blinking outside my window. They don’t know about climate change, but let’s hope that they can adapt to the changing conditions. What would summer be without them?

With photo