Bugs Matter: counting insect ‘splats’ on vehicle number plates [pdf]

> This is contrary to a suggestion that finding fewer insects on number plates in recent years might be attributed to increasing streamlining of vehicle aerodynamics over time. Our data show that newer vehicles sample more insects than older vehicles, and we have observed pattern of fewer insects on number plates more recently than in the past in spite of this effect of vehicle age, which is assumed to be correlated with aerodynamics.

In fact the researchers posit a few more possiblities other than collapse of insect populations that could explain their data. For example they can't eliminate the possibility that there's some change in the management of roadside verges that specifically decreases the insect population in those environments, without reducing the population in other environments.

The challenge for all the explainations which involve something other than population change is that there's now an increasing nubmer of studies using different techniques which consistently show declining populations. For example [1] uses Malaise traps in nature reserves, which presumably wouldn't be affected by roadside management practices, and finds a ~75% decrese in flying insect biomass over 27 years, whereas [2] uses light trap data to look at moths specifically and finds a ~40% decline in biomass over 50 years (and ~50% in woodlands).

Whilst it's possible to find studies that show increases in insect numbers e.g. as a result of site-specific conservation work, there's a lot of data suggesting that in Europe at least numbers are in significant decline. As far as I can tell (and I'm really not an expert) we don't understand the reasons all that well, but habitat fragmentation and pesticide use are leading theories. We at least know that common pesticides (notably, but not exclusively, neonicotinoids) are toxic to bees, and will reduce populations even at sub-lethal doses (e.g. [3]). So changing our agricultral practices to eliminate these chemicals looks like a necessary, but perhaps not sufficient, part of the solution.

[1] https://journals.plos.org/plosone/article?id=10.1371/journal... [2] https://resjournals.onlinelibrary.wiley.com/doi/10.1111/icad... [3] https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.66...

Here's a big list, for anyone interested in some numbers: https://en.wikipedia.org/wiki/Automobile_drag_coefficient

Not doubting you just genuinely interested as an enthusiast. edit: saw your other reply

    $ gti
          ,---------------.
         /  /``````|``````\\
        /  /_______|_______\\________
       |]      GTI |'       |        |]
       =  .-:-.    |________|  .-:-.  =
        `  -+-  --------------  -+-  '
          '-:-'                '-:-'

incorrect

As I've pointed out in another comment, research has shown [0] that counter-intuitively "modern cars actually hit slightly more insects."

It's a reasonable hypothesis, however what this research shows is that we would have expected to see more dead insects on cars had populations remained stable.

0. https://www.theguardian.com/environment/2020/feb/12/car-spla...

It depends on what the nature of the airflow around a specific car looks like. Bugs have a harder time than air making a "hard corner" but the mass of air stuck at a hard corner can cause other air to go around in a more graceful way and carry the bugs with them.

Coefficient of drag hasn't improved much since the 90s and most of those improvements have been with regard to the vacuum behind the car so aerodynamics is probably only a contributing factor either way.