The Fading Insects Myth

Written by Dr Klaus L.E. Kaiser

Discover magazine is warning us of the next calamity to hit the globe, namely fading insects, specifically light-colored dragon flies. Not only are the insects’ colors fading, their numbers may be doomed as well. According to a new study published in the journal Nature Communications by scientists from several universities in Europe, Christie Wilcox reports “of all the species affected by climate change, the insects should be more feared for than any other group.”

You wouldn’t know that when you are outdoors at a time when the blackflies and mosquito larvae hatch from their water-stage into full-winged airborne little pests looking for your blood.  Not even a contingent of well-armed Royal Canadian Mounted Police officers could keep them at bay, as Royal visitors to Canada’s northlands experienced. But it’s not just humans the insects pursue, native wildlife like deer and moose can also be driven crazy when the bloodsuckers emerge en masse. That’s when you need dragonflies.

Dragonflies

Dragonflies, like the Yellow Striped Hunters (Austrogomphus spp.) are also insects. Their larvae, called nymphs, also live in water and feed on the larvae of blackflies and mosquitos. The winged adult dragonflies do the same with the airborne adults of our little “friends.”

Now let’s look at some of the claims published in the journal. The abstract of the article says “Here we show, using data of 473 European butterfly and dragonfly species, that dark-coloured insect species are favoured in cooler climates and light-coloured species in warmer climates.” So far so good, but then comes the great revelation – and the accompanying colorful pictures (like Fig. 1) appear to support it: Kaiser fig 1

 “By comparing distribution maps of dragonflies from 1988 and 2006, we provide support for a mechanistic link between climate, functional traits, and species that affects geographical distributions even at continental scales.”

What’s Wrong Here?

For that, you need to read and follow all the details given, including the many assumptions, model inputs, statistics, and the supplementary information for the paper. From that, you will get a different view.

To begin with, the authors appear to confuse the term “species” with the term “specimens.” For example, throughout the paper and also in the supplement, the authors talk about “species.” However, when you look at the Supplementary Figure 1, you quickly realize the problem. While the caption of that figure reads “We measured the colour value of the …. thorax and abdomen of 107 species of dragonflies and converted the values to a grey scale” it is clear they only measured 107 individual dragonflies, not thousands of such across many species, as apparent from Fig. 2 (shown below; supplementary figure 1 in the supporting document). kaiser fig 2

Fig. 2 shows  Measured distribution of color values of 107 dragonfly bodies, converted to gray scale; lightness (color value) on abscissa and frequency (number of observations) on ordinate.

Well, that’s a vast difference!

The difference between the terms “species” and “specimens” is like the difference between, say, the total number of people in 100 nations of many millions each and 100 persons only. For example, Europe has only some 200 biological species of native mammals but many millions of specimens of their kind.

The Upshot

By my reckoning, the authors of this study (four from Germany and one from Denmark/UK) mis-translated the German term “Spezien” (meaning samples or individuals) with the English term “species.” On second thought, the high level of detail and general language of the text does not appear to be commensurate with such an error; the term “species” has a precise and different meaning in the field of biology. At the very least, any serious peer review of that paper ought to have noted and queried this misleading terminology in this context.

As to the colorful 2,000-pixel map of Europe (Fig. 1), in fact it is nothing but a temperature chart where the legend has been changed from cool (temperature) to “dark-coloured” (dragonflies) and from warm to “light-coloured.” 

Overall, it looks to me like a big splash of nothing. The claimed fading is only based on a computer model with umpteen assumptions and caveats using a sample size of 107 dragonfly bodies for all of Europe. There’s no need to worry about fading insects or climate change but, perhaps, about scientific rigor and language.

Dr. Klaus L.E. Kaiser  Bio

Dr. Klaus L.E. Kaiser Most recent columns

Dr. Klaus L.E. Kaiser is author of CONVENIENT MYTHS, the green revolution – perceptions, politics, and facts convenientmyths.com

Dr. Kaiser can be reached at:mail@convenientmyths.com

 

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