The Windscreen Phenomenon

Michael - Thursday

The odd thing about the windscreen phenomenon is that it’s about what isn’t there. And some people wonder whether the phenomenon exists at all. Simply put, it’s the fact that when you drive some distance, your windscreen isn’t covered with squashed insects collected as you drive through the countryside. The implication is that the number of insects has significantly decreased over the years. That’s the windscreen phenomenon.

So, there are several issues with this. In the first place, it only applies to flying insects. No one checks how many creepy crawlies their tires have run over. Secondly, cars have developed much more aerodynamic bodies – perhaps the insects are caught in the slipstream over the vehicle. And one school of thought is that that the whole thing is perception – there is no phenomenon. (Remember how big Texas was when you were young?) Personally, I’ve just driven from Johannesburg to Knysna (about 800 miles) and I had some splatter, although not as much as I would get in the summer or in a moister area than the semi-arid Karoo in the center of the country. Maybe, it’s not a global effect (if it exists at all). The main problem is that it’s all based on anecdotal evidence, and insect populations are notorious for their boom and bust behavior in any case.

And then we can ask if we should care. Would a drop off in the populations of flies and beetles necessarily be such a bad thing? What about the diseases they spread and damage they do? And butterflies and moths are pretty to look at, but many of their caterpillars are food pests. As for mosquitoes and biting midges…

Here the answer is pretty clear. Insects sit at the bottom of the animal food chain and overall they are a vital basis for the global ecosystem. Butterflies and moths pollinate plants. Bats eat hundreds of times their body weight in mosquitoes and midges. Flies and beetles help with recycling decaying material. We’ve all heard of the dire effects of the decline in bee populations which is forcing hand (and recently drone) pollination of almond trees in California. And they all form a key protein source for animals and birds and even people. (Harvesting the caterpillars of the giant silk moth – ‘mopani worms’ – is a small industry in Botswana.)  The list is endless. The eminent biologist Edward O. Wilson has warned: “If all mankind were to disappear, the world would regenerate back to the rich state of equilibrium that existed ten thousand years ago. If insects were to vanish, the environment would collapse into chaos.” So, yes, we should care.

If the windscreen phenomenon is real, what could be causing the decline? Insecticides is the obvious answer. The effect on insectivorous birds is well-documented – it’s fifty years since Rachel Carson’s book Silent Spring woke people up to that. Presumably the effect was also significant to the insect population – after all that was the point. There are various other suggestions around – including that the windscreens themselves are partly responsible – but, again, most of the evidence was from casual observation. That’s why a recent study from Germany made the headlines.

Members of the Krefeld Entomological Society at work

Interestingly, it wasn’t based at a well-known university or research organization the way most such studies work. It was mainly driven by a group of amateur field naturalists from an entomological society. They have been documenting flying insect populations in 63 nature reserves over almost thirty years. Over that time period, the insect populations studied have declined by between 70% and 80% depending on the season. The study also recorded weather conditions, and the decline has been ongoing, so it seems unlikely that it can be put down to global warming.

Other evidence has been coming out of North America that suggests something similar, and a recent report from Australia reported similar declines there. The bottom line is that no one seems to have a very clear idea of why this so-called “insect apocalypse” is occurring or what we could do to reverse it. Maybe we need to find out!