For almost 30 years they passed as quirky eccentrics, diligently setting up their insect traps in the Rhine countryside to collect tens of millions of bugs and creepy crawlers.
Now the group of German entomology enthusiasts can boast a world-class scientific treasure: evidence of what is described as one of Earth’s worst extinction phases since the dinosaurs vanished.
Insects, which comprise two-thirds of all terrestrial species, have been dying off at alarming rates, with disastrous impacts on food chains and habitats, researchers say.
The home of the Amateur Entomology Society of Krefeld on the Dutch border is a former school building where thick curtains block out the sunlight.
Inside in glass cabinets are stored thousands of butterflies, their wings bleached by time, along with exotic fist-sized beetles and dragonflies, brought back from around the world by amateur collectors.
Treasure trove
Traditionally “entomology was mainly about drying and collecting rare specimens,” says the society’s president Martin Sorg, wearing John Lennon-style glasses, a multi-pocket jacket, and sandals.
He and an army of volunteers have over the years gathered as many as 80 million insects that are now floating in countless ethanol bottles.
Each bottle contains the amount caught by a single insect trap over a set period, and each box represents a collection of such catches over nearly three decades.
“Since 1982, the traps we manufacture ourselves have been standardized and controlled, all of the same size and the same material, and they are collected at the same rate in 63 locations that are still identical,” explains Sorg.
The result is a treasure trove of quantitative data that dwarfs that of any funded university project, he says.
But if he is visibly proud of the society’s research, the outcome terrifies him: in the test period, the total biomass of flying insects here has plummeted by 76 percent.
Quaint Sunday hobby
To demonstrate the rapid decline, a lab technician holds up two bottles: one from 1994 contains 1,400 grammes of trapped insects, the newest one just 300 grammes.
“We only became aware of the seriousness of this decline in 2011, and every year since then we have seen it get worse,” says Sorg, the man who sounded the alarm.
At the time, the news didn’t make major waves outside ecological circles.
Concern about biodiversity loss focused mostly on large charismatic mammal species, and environmental monitoring such as that in Krefeld was considered a quaint Sunday hobby, largely ignored by the scientific community.
Also in 2011, just across the Dutch border, ecology professor Hans de Kroon was working on the decline of birds in the region.
He hypothesized that the birds suffered from a shortage of food, especially insects, but had no data to prove it.
“Then our German colleagues from Krefeld got in touch and said, ‘we have the data, we’ve witnessed a strong decline, we are very concerned, could you analyse the data?’.
“That’s how it all started.”