This forum is about wrong numbers in science, politics and the media. It respects good science and good English.
I noticed this article in the Guardian last month by Damian Carrington:
Extract from the article:
"The abundance of flying insects has plunged by three-quarters over the past 25 years, according to a new study that has shocked scientists.
Insects are an integral part of life on Earth as both pollinators and prey for other wildlife and it was known that some species such as butterflies were declining. But the newly revealed scale of the losses to all insects has prompted warnings that the world is “on course for ecological Armageddon”, with profound impacts on human society.
The new data was gathered in nature reserves across Germany but has implications for all landscapes dominated by agriculture, the researchers said.
The cause of the huge decline is as yet unclear, although the destruction of wild areas and widespread use of pesticides are the most likely factors and climate change may play a role. The scientists were able to rule out weather and changes to landscape in the reserves as causes, but data on pesticide levels has not been collected.
“The fact that the number of flying insects is decreasing at such a high rate in such a large area is an alarming discovery,” said Hans de Kroon, at Radboud University in the Netherlands and who led the new research.
“Insects make up about two-thirds of all life on Earth [but] there has been some kind of horrific decline,” said Prof Dave Goulson of Sussex University, UK, and part of the team behind the new study. “We appear to be making vast tracts of land inhospitable to most forms of life, and are currently on course for ecological Armageddon. If we lose the insects then everything is going to collapse.”
The research, published in the journal Plos One, is based on the work of dozens of amateur entomologists across Germany who began using strictly standardised ways of collecting insects in 1989. Special tents called malaise traps were used to capture more than 1,500 samples of all flying insects at 63 different nature reserves."
A couple of things that I noted when I first saw this article are: 1) Carrington is claiming that the total population of all insects has reduced by 75%, whereas it is really the total weight of collected insects that is decreasing, and it may be that some of the larger species of insects are declining in numbers and are skewing the statistics; 2) the type of insecticides that the Greenies have been campaigning for years to ban, neonicotinoids, have already been banned since 2013 in the EU (it is not totally banned as yet, but is banned for use on crops which are regarded as attractive to pollinating insects like bees), but there is no significant increase in the collected insect figures since 2013 according to the graph provided in the Guardian article.
I didn't think any more of Carrington's article until last week, when I noticed that the new UK environment secretary, Michael Gove, has announced in the Guardian that he proposes to go along with the idea of banning neonicotinoids (the UK has previously always voted against banning neonicotinoids), and Gove mentions that the Carrington article and the German insect study has influenced his decision.
Gove proposes insecticide ban
You don't really want to be basing public policy on something written by Damian Carrington.
I also noticed that the Green-leaning Ecologist magazine has produced an article, based on talking to various insect research people, about the German study and its news coverage:
The Ecologist article picks up the point that I mentioned above in this extract:
"Importantly, the study did not measure insect populations, as most articles claimed, but insect biomass. In other words, the researchers measured the insects caught in traps by weight, not by number, nor species.
This is a subtle, but important distinction, according to Chris Shortall, an entomologist at Rothamstead Research, which has been surveying insects since 1964.
"This decline could very well have been driven by a decline in one or two relatively large taxa (such as bumblebees and dragonflies) as was demonstrated in our study at Hereford which found one species of (relatively) large fly had declined, while other taxa showed no significant change," he said."
The Ecologist article also mentions similar insect population studies in the UK which have shown less disturbing results:
"Other research on insect populations have drawn mixed conclusions. A study published in the journal Global Change Biology in 2015 looked at the impact of extreme weather, climate and pesticide use on invertebrates in Sussex cereal fields over 42 years.
It found that populations of 12 insect species declined and two increased. Of the remainder, some recovered then declined. However, overall it identified a 35 percent decline in the total number of insects.
Of four insect traps studied by the scientists at Rothamsted Research, three showed downward trends in insect biomass over 30 years to 2002, but the decline was only significant in one area."
The last couple of paragraphs in the Carrington article also mention the issue of motorists seeing fewer insects splattered on windscreens over the last few decades:
"Another way of sampling insects – car windscreens – has often been anecdotally used to suggest a major decline, with people remembering many more bugs squashed on their windscreens in the past.
“I think that is real,” said Goulson. “I drove right across France and back this summer – just when you’d expect your windscreen to be splattered all over – and I literally never had to stop to clean the windscreen.”"
Personally I think that motor vehicles wiping out insects might actually be a major reason for the decline in insects over the decades. I remember noticing all the insects that got splattered on a windscreen when I first started driving at the end of the 1970s, and it occurred to me at the time that motorists were effectively engaged in something a bit like Chairman Mao's fly swatting campaign of the late 1950s in China. In the Mao fly swatting campaign, Chinese citizens, including children, had to go around swatting flies. The quota was for everyone to swat 10 flies per day and put them in a matchbox to be presented to a local communist party official. The campaign resulted in about 100 million kg of flies being killed. But so many flies got killed after a year or so that it became difficult to achieve the 10 per day quota. The Chinese could not swat flies using motor vehicles as they all rode bicycles back in Mao's day.
I'd be a bit cautious of the fly on the windscreen evidence unless someone where to drive the same car today they drove back then as ever more attention is paid to aerodynamics and it may be that insects are being carried over the roof of the car and away from the windscreen.
Used to have aerofoils on the windcreen wipers at one point to maintain contact between the wiper blade and the screen but fewer cars have those now.... because of changed wiper design or aerodynamics?
We don't know unless the observation is made under identical conditions as previously.... too many factors to consider.
That's a good point J, that the aerodynamic design of cars may have improved a bit over the decades, and that might be contributing to the perception that insects are in decline.
There was an attempt to quantify the number of insects being splattered by cars by the RSPB charity (Royal Society for Protection of Birds) back in 2004, which involved a device distributed to a substantial number of UK motorists called a 'splatometer', described in this BBC news article:
The splatometer was basically just a piece of cardboard with gridded squares that was attached to the car's front numberplate, and 40 thousand UK motorists participated in the exercise. Use of the front numberplate to assess splattering would be expected to reduce the importance of the issue of the aerodynamic design of the car, but it might also concentrate on the proportion of the insect population that tends to fly about a foot above the ground.
The results from the exercise in 2004 were that one insect got squashed for every five miles of road travel. Presumably in the years after 2004, RSPB staff have then continued to use the splatometer themselves to monitor the UK insect population, and the absence of news stories about the splatometer since then suggests that the insect population measured by the device has not declined further.
One insect getting squashed every five miles means that it would take only 50 miles of travel by car to get to Chairman Mao's 10 per day fly swatting quota, and that would be achieved just with a portion of the front numberplate of a car.
By the way, I seem to recall an article many years back about the French fondness for Frogs legs.
It appeared that in India the harvesting of frogs proved a modest but appreciable money earner with the consequence that so many frogs were dismembered (and many of them while still alive) that the insect population exploded where this took place.