Firefly Watch 2022

The 2022 season of Firefly Watch was the most disappointing so far. There was a dramatic decrease in the number of flashes counted from 2021, which was a decrease from the previous season. Run by Mass Audubon, Firefly Watch monitors populations of fireflies nationwide, using citizen science observations. Observation protocols are simple. Count how many flashes you see in three separate ten second periods. I space mine ten minutes apart to get varying levels of darkness, starting just before sunset. We also record the flash pattern (single, double, or triple flash for instance), start and end times, wind, precipitation, and temperature. For good measure, I also record the colors of the flashes. I start at the end of May and depending on how long I keep seeing fireflies, I go until late August or early September. I use the same location every year to track the same population, and try to stick to the same dates every year. This year the dates for my second observation of the week were a day later than last year. I end the season when I go two consecutive observations with no fireflies. The latest I ended was September 26 in 2018. This year I ended on August 24, the first time I didn't make it into September. The last firefly I saw was August 7, so I actually went beyond the two night standard. 2022 saw a decrease of 94 flashes from 2021, nearly a 16% drop. That's close to 30% fewer than 2020, the highest count so far. The charts below show the population trends. Chart 1 shows each year's counts by date and how the number of flashes observed changes within the season. Chart 2 shows each year's total counts side by side.

While I could use rainy nights in 2021 as a partial explanation for the decreased count, I only had rain during one or two observations this year. This summer was abnormaly dry, but not quite a drought. Not enough rain could be a possible cause. Other factors include light pollution, although the amount of light is unchanged year to year, and pesticide use, but I have no way to measure who is using what pesiticides in the neighborhood. One final explanation is that the neighbors cleared some vegetation from their small woodlot in the back yard. I'll continue monitoring and hopefully the negative trend will reverse itself.