Insect Abundance In Steep Decline

"Insect numbers are way down. It's a little under the radar from the public perspective, but it's really high on the radar in terms of research."
Jeff Skevington, entomologist, Agriculture Canada

"It's unfortunately a little bit informal in terms of measurements [bug census]."
"Like, 'How pasted did your windshield get?' is not a normal scientific measurement. But it is something that I think many people have noticed."
"The general trend is something I myself have noticed and thought about on many occasions."
"It's a big deal, right? When you think about this it sounds kind of nuts, but the number of insects splattering on your windshield is a really good indication of just how abundant life is in the environment."
"It's anecdotal, but if it's true there seems to be a lot less life out there than there used to be. And that is not something we should be ignoring."
Jeremy Kerr, ecologist, entomologist, University of Ottawa

"Every spring since 1989, entomologists have set up tents in the meadows and woodlands of the Orbroicher Bruch nature reserve and 87 other areas in the western German state of North Rhine-Westphalia. The tents act as insect traps and enable the scientists to calculate how many bugs live in an area over a full summer period. Recently, researchers presented the results of their work to parliamentarians from the German Bundestag, and the findings were alarming: The average biomass of insects caught between May and October has steadily decreased from 1.6 kilograms (3.5 pounds) per trap in 1989 to just 300 grams (10.6 ounces) in 2014."
"The decline is dramatic and depressing and it affects all kinds of insects, including butterflies, wild bees, and hoverflies,” says Martin Sorg, an entomologist from the Krefeld Entomological Association involved in running the monitoring project."
Christian Schwägerl -- Yale Environment 360

Fireflies, like these in a forest in the Netherlands, have disappeared from some areas in North America and Europe where they were once abundant. PAUL VAN HOOF/MINDEN PICTURES

Scientists are concerned and with good reason, at the mysterious disappearance of once-abundant insect populations. Where once we commonly saw and heard seasonal insects of all varieties in our environment, their sounds and sightings are now seen to be far less frequent; there has been a sustained and huge drop in their abundance. This is important for a number of reasons, not the least of which is their vital function in crop pollination.

They also represent a food source for insect-consuming birds. When such birds cannot find their in-flight or stationary food source, they decline in numbers as well. So, in lock-step with a diminishing number of insects, the birds that rely on them to sustain themselves in nature's chain of symbiotic existence, are unable to thrive, and they too become rare. Across Europe and North America the insects once so commonly seen just a generation ago have realized a steep drop in numbers.

Although the cause remains a mystery yet to be solved, along with a possible solution, suspicion has turned to what might be obvious to many; the agricultural use of pesticides. The insects that pollinate plants that all animals consume are becoming scarcer and the potential of other collapses resulting from theirs is of real concern to scientists. Populations of many insect-eating birds such as swifts, swallows, nighthawks, martins and flycatchers are present in much smaller numbers than usual.

According to a major conservation group, Bird Studies Canada, annual bird counts have noted declines of 50 to 70 percent in these species, attributing lack of insects as the likely cause. An increase in evidence has led entomologists to inspire new ways of detecting the absence of the once-thriving insect population. In 2013, A German biologist, Axel Ssymank, set out to update a 1989 insect count in a German nature preserve.

He undertook new counts taking the same area with a similar trapping method as the original, to discover that 80 percent fewer insects were present, despite the fact that the area represents a protected reserve. He returned a year on and the same result occurred. "He got audible gasps from the scientists. I don't think anyone knew just had bad it was", said Dr. Skevington, of a conference at which Ssymank presented his dismal results.

Hover flies, often mistaken for bees or wasps, are important pollinators. Their numbers have plummeted in nature reserves in Germany. JEF MEUL/NIS/MINDEN PICTURES/NATIONAL GEOGRAPHIC CREATIVE

At Queen's University, biologists discovered a deep pile of guano from chimney swifts in a building on campus and undertook to date the droppings by each layer to discover that as DDT use in the 1950s accelerated, birds turned from feeding on beetles which DDT destroyed, to alternatively consuming lower-quality insects such as stink bugs. That marked the start of the decline of chimney swifts to the present time where their population has fallen by over 90 percent.

Dr. Skevington points out that most studies have taken place in Europe and have focused on flying insects. His colleague at Agriculture Canada, Henri Goulet, has studied insects for a half-century, and he sees non-flying insects disappearing at the same rate as those that take flight. Species of beetles he once studied no longer exist at the Central Experimental Farm, and he believes the change began as Ontario farmers took to growing more corn and using herbicides on cornfields.

Of all flying insects to be imperilled, it seems to be the useful ones for the most part. The bane of peoples' summertime existence, mosquitoes, appear to have been untouched by the decline, likely as a result of their habit of laying eggs in pools remote from pesticide use.

(GRAPHIC) G. GRULLÓN/SCIENCE; (DATA) M. SORG ET AL., MITTEILUNGEN AUS DEM ENTOMOLOGISCHEN VEREIN KREFELD 1, 1–5 (2013) © 2013 ENTOMOLOGISCHER VEREIN KREFELD