An increasingly unusual sight, a grill covered in insects. Photo: Robert, Creative Commons, some rights reserved
August 13, 2020 – Curt Stager reports on a long-term study with flying insects in Germany, in which an astonishing 76% decrease in the total biomass of flying insects was recorded in the last 30 years. This is not a decline as in a single species, but seems to affect the entire range of species.
Martha Foley wonders if this could explain the drop in insectivorous birds popping around her home or the sharp drop in insect bites Stager has seen on his car compared to decades ago.
Disturbing news from long-term studies and anecdotal observations.
MARTHA FOLEY: So I think of two things. First – we talked about the importance of naturalists and wrote down your observations. We also talked about the importance of long-term observation. You know, in detail, that’s what is happening in this place at that point. And now you come to the news of this study in Germany, this 30-year study of insects – just to watch the loss of insects and I just wonder if you can talk about it and why we don’t have any more information about it?
CURT STAGER: Yes. It’s really, really interesting. It was a surprising and disturbing story that came out in 2017. It was a 27-year-old, long-term, drawn-out, otherwise boring study conducted in dozens of remote protected areas in Germany where scientists set up these traps that look like a tent on the ground with an open front and flying insects of all kinds, Day and night, flew in, and then they hit the wall of the tent and went to the top where there was a collecting jar. And day after day, year after year, they collected what was in the jars and dried them and weighed them. It’s that simple. You’d never have noticed, but as they hit their data for the past three decades, the weight – the biomass – of flying insects dropped 76 percent across the board, which is incredibly fast and disruptive for many reasons.
FOLEY: And what? Did you find out that this is all some kind of bug that just goes away or …?
STAGER: Well, that’s the first thing that would shock an ecologist overall because we’ve heard of decreases in honey bee pollination, we say, and that’s because beekeepers would notice. Or some other charismatic thing, a certain type of moth or butterfly, and people may have been monitoring that, but those are many types. This is the total mass of flying insects across the board. So that would include wildly different types of insects, not all of which are just bugs. There would be many types of bees, wasps, and hornets. Many types of flies – from house flies to mosquitoes.
FOLEY: Moths.
STAGER: It could be butterflies. This is a completely different group. Dragonflies. Beetles – that includes fireflies and all these other things. So, maybe to compare it with more well-known groups of animals. If they were mammals instead of insects it would be as diverse as something that affects all wolves, foxes and coyotes, the entire cat family, the entire weasel family, and so on.
FOLEY: Wow. We would have noticed.
STAGER: So you think you’d notice, but you can only be really sure you’re getting the numbers. And luckily these people had.
FOLEY: So the other thing I’ve thought about to note and write things down is how we act with anecdotes. Over the years I believe I have noticed a real decrease in the number of swallows in my yard that are harassing the cat. We used to have trouble keeping them out of the barn. They were everywhere – tree swallows and barn swallows. And now we just don’t see them. We see a pair of tree swallows and maybe a nest full of swallows. So, I have this anecdote; Nothing supports my narrative, but I just think about it.
STAGER: Right, without data to back up everything is just an opinion. Many scientists in other fields besides insect experts say, “Oh my god, maybe that explains the decline in insectivorous birds.” Or other people say, “Gosh, I wonder if it’s going to happen here.” So that’s what happened to me. I have a nature journal that I’ve kept for years, but I’ve never written down the insects. But I remember driving in the New England summer of the 1960s and 1970s as a teenager and your car and windshield were covered in smashed insects
FOLEY: Plastered! Yes.
STAGER: Yes, and there were even special products that you could buy to remove the insects. I remember driving at night and enjoying the sparks of fireflies glowing in the dark on my windshield. That’ll never happen again. I never clean my car. I hardly ever cleaned my windshield, and there was even a study of people studying bug spills on license plates and on the fronts of cars. So I tried it myself when driving from Saranac Lake to Paul Smith’s and I didn’t get a single splash. So again, it’s like many of us might notice the decrease in bug splats.
FOLEY: It’s a shame we didn’t have this 30 year study of your car.
STAGER: Yeah.
FOLEY: So, keep your eyes open and write it down.
STAGER: Yeah.
FOLEY: I bet we’ll hear more about this little piece of news.
