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Insects disappearing: pesticides, climate change, …????

October 23rd, 2017 · 3 Comments

Friday night, at my niece’s birthday party,the conversation turned (not started by me … surprisingly) to news from Germany: the insects are disappearing.

? Dragonfly ?abundance of flying insects has plunged by three-quarters over the past 25 years

In this serious study (peer-reviewed publication: More than 75 percent decline over 27 years in total flying insect biomass in protected areas), that involved surveys from across German nature reserves and natural areas, the pattern is pretty much consistent: numbers and mass of flying insects have shown a precipitous decline.

This is a survey and definitive work: like with bees, hypotheses as to why the insects are disappearing with varying degrees of substance but no certainty as to why.

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.

Truly — we don’t know “why” but we do know it is occurring, that insects are disappearing.

This is Germany, one might suggest, and somewhere — someone — might be thinking/suggesting that this is somehow a German phenomena (looking at the timeline, German unification kills insects as hypothesis?) but there is global work showing declines in insects. From the article:

Current data suggest an overall pattern of decline in insect diversity and abundance. For example, populations of European grassland butterflies are estimated to have declined by 50% in abundance between 1990 and 2011.

Going back to that birthday party conversation, illuminating ‘bringing it to personal life’ comments included this observation for any/all that does long-distance driving:

I used to have to stop, multiple times, to clean the car windshield of dead insects when driving to Cleveland to visit my family. Now, I can go there and back and there might not be a single bug …

focus on the bugsThat sparked me to thinking … having gone to school in the Midwest (too many) decades ago, those drives would eat up windshield wiper fluid and the car’s grill would be filthy at the end of the drive. Driving my eldest to school in the Midwest (with detour to Kentucky for the eclipse …) this August, in what one might consider to be peak insect season, I did not have to clean the windshield of insects once during the entire trip and, thinking back, I don’t recall having to clean any insect remains from the car at the end of the trip.

From decades-long (amateur) scientific data gathering to the car’s windshield, the ominous situation seems clear: insects are disappearing.

Should we care?

Sunday evening, at a dinner party, a friend sparked a conversation starting with ‘I hate mosquitoes … this is an insect that shouldn’t exit …’ If we think of that in terms of the disappearing insects, sort of like the people who react to a record-breaking warm day in January with ‘if this is global warming, give me more of it’, many people see flying insects as pests to detest and likely would welcome hearing that they’re disappearing.  (NOTE: that is not that friend — whose comment really was more focused & even nuanced …)

But, flying insects aren’t some abstraction, some ‘other’ irrelevant for ecosystem health and, fundamentally, human existence. From the article’s introduction,

insects play a central role in a variety of processes, including pollination [12], herbivory and detrivory [34], nutrient cycling [4] and providing a food source for higher trophic levels such as birds, mammals and amphibians. For example, 80% of wild plants are estimated to depend on insects for pollination [2], while 60% of birds rely on insects as a food source [5]. The ecosystem services provided by wild insects have been estimated at $57 billion annually in the USA [6].

And …

Gastronomy implications

Now, another portion of last evening’s dinner conversation (with various degrees of disgust … though not from me) was the growing move to commercialize human food from insects (or entomophagy … by the way, some restaurant options for exploring insect-based cuisine). Taking us back to another reason to think about and be concerned about disappearing insects.

It’ll be ok if we kill off all the animals. We can still eat insects! Wait..what? 

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Tags: climate change · science

3 responses so far ↓

  • 1 Greg Laden // Oct 23, 2017 at 10:26 am

    Great post. I was thinking about blogging about this, but now I can just tweet out your post!

    This is a complicated issue. My thoughts:

    This is important work and this is an important finding.

    There are very significant open questions that relate to both the cause of the decline and the ability extrapolate. The researchers did not look at the impact of agricultural practices, and I’ll bet any amount of dollars against any amount of donuts that is a major factor .

    The study does not adequately compare across taxa on the basis of life cycle. They are only looking at adult flying insects. In temperate biomes, adult flying insect mass is mainly made up of things that eat grass and things that hatch from bodies of water en mass (lake flies, dragon flies, etc.) Small changes in habitat management or agriculture can make huge changes in either factor.

    For example, remember that wheat = grass, changing from wheat to potatoes in field, or reversing that change, can cause changes in biomass either because the habiats are changed more towards a grass eater, or because anti-insect measures are increased/decreased.

    The fact that this is a fairly steady decline over time with almost no decadal variation ruled out climate change for the researchers, and it seems to also limit a lot of other explanations. It, however, implicated agricultural development and/or the built landscape, or both, because those tend to be steady changes over time that are highly buffered (as opposed to, say, the extent of marginal wetland as dry vs. wet cycles occur at the decadal scale).

    I would be very cautious about extrapoling this huge number. Trapping programs are ubiquitous, being done everywhere. If there was a ~70% decline in insects, or just flying insects, globally, it would show up just as, say, a sudden 1C increase in global temperature would. This is just this one area. (They refer to a very small number of other studies)

    I take this study not to indicate a specific global problem, but rather, to expose what probably is a global vulnerability.

    I look forward to followup work. I recommend not basing too much on this specific decline number because that messaging will have to be walked back later.

  • 2 A Siegel // Oct 23, 2017 at 10:34 am

    Greg: Thank you for this thoughtful and substantive comment.

    Re global: the ‘75%’ certainly seems, like the points you make, something that one should not extrapolate as a ‘it is happening just like this globally — to same extent’. However, it does seem (TO BE CLEAR — not expert in the field) that this aligns with other work / data around the planet. (And, well, of course my and friends’ windshield wiper experiences are definitive evidence …).

    Eg., your point is well taken about the complexities of this, multiple factors, and risks of extrapolating too far — especially not with the specific ‘75% over 27 years’ …

    PS: Something important here: the value streams of long-term, dedicated, deliberate scientific work — data collection & analysis — which merits continued and reliable government support (even if, in this specific situation, much of this looks to have been volunteer science …).

  • 3 Tenney Naumer // Oct 24, 2017 at 6:49 pm

    I drove in August 2014 from southern Illinois to Fort Worth and had about 2 or 3 very small bug splats on the very large windshield of my 1996 Tahoe. On the way back, this August, driving a 16-ft Penske rental truck, I had perhaps 5 gnat splats. I did however see about 5 butterflies, so that was nice.

    When I was in high school, we’d have to clean the bugs off the radiator grill a good twice a day, the dead bugs were so thick on it.

    In Texas, I had a tiny second-floor balcony, and I would often sit out there in the evening with the lights on and the door open and nothing, NOTHING, would fly in the door!!!!!

    I lived on the very western edge of Fort Worth and there were trees and grass, but no bugs.

    Here locally the county sprays RoundUp along the edges of the highways. In the fall, back in the 1990s, there used to be thousands of woolly bear caterpillars crossing the roads. In 2012, I saw perhaps 4 in total.

    I think I’ve seen a grand total of 5 fireflies in the past 7 years. As a kid, I would go outside at night and just walk with my arms stretched out with my hands open and catch all I wanted to put in a jar and watch them blink in the darkness of my bedroom.

    There used to be literally millions of starlings flying north to south or south to north during their migrations — amazing undulating waves of them that lasted for hours. They’d land overnight in everyone’s trees and the next day people would have to spend a lot of time hosing down their sidewalks.

    Now, there are perhaps a 100 at a time.

    Sure habitat destruction is one reason, but the biggest reason is the pesticides and herbicides.