It’s not just bees and butterflies that are vanishing. It’s many, many other insects too. In yet more evidence that we are in the throes of Earth’s sixth mass extinction, a new study reports that flying insects have declined precipitously in just 27 years in parts of Germany.
We may feel less inclined to save some of these creatures – the midges, aphids and parasitoid wasps – than our trusted pollinators. In fact, motorists might welcome the absence of squashed critters on their windshields. Gardeners may take pleasure in the idea of growing plants free from aphid pests. Even tourists, enthralled by the notion of travel without the midge bites, might see this as a cause for celebration.
But if this estimate is right, this loss is huge, both in scale and implication. Previous reports have found a decline of up to in recent decades, but this new work suggests a much higher toll, and possibly across hundreds or even thousands of species that visit nature reserves year on year.
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In the clearest analysis yet of the plight of flying insects, Dutch and British researchers used data collected over nearly three decades by insect enthusiasts. These hobby biologists sampled 63 German nature reserves, covering a range of habitats including meadows, sand dunes and heathland, from 1989 to 2016.
Caught in a trap
Each reserve was sampled once every few years to avoid damaging wildlife populations, and all samples were taken using identical “malaise traps”. These tent-like structures ensnare insects flying about a metre above ground, before funnelling them into a collection jar where they drown in alcohol preservative.
By comparing the contents of each trap, the team found that in the 27 years of sampling, the total mass of these creatures plummeted across all habitat types. The most serious declines – 82 per cent over that period – occurred in mid-summer, when the insects are typically most plentiful.
No one knows whether this is happening elsewhere on the same scale, or what is causing it. In this study, atmospheric warming and changes in land use were considered unlikely culprits. Instead, one possible cause is that modern agriculture is responsible, killing steadily and so quietly that the scale of this loss has – until now – gone largely unnoticed.
The study authors speculate that neighbouring fields dowsed in pesticides, such as neonicotinoids, may become places from which insects never return. And so, despite the good work being done in maintaining protected areas, what’s happening elsewhere is affecting life everywhere.
Knock-on effects
Although the casualties are tiny, their demise will have big consequences. If we lose the insect predators of leaf-munching bugs, it follows that we may suffer more crop plagues. In the same vein, the discomfort of midges is a necessary byproduct of a planet that provides enough food for birds.
In less than three decades, three-quarters of the insect food for species such as swallows has been wiped out from the sites investigated here. A catastrophe of this scale reverberates throughout the entire ecosystem.
Conservationist Rachel Carson once warned of the damage of unfettered pesticide use in her book Silent Spring. More than half a century later, we’re still facing this predicament. To the question, “Where have all the insects gone?”, the only reasonable retort can be, “When will we ever learn?”.
PLOS One
