Insect Population Crash

Scary news from Australia:

• Marc Rigby, Insect population decline leaves Australian scientists scratching for solutions, ABC Far North, 23 February 2018.

I’ll quote the start:

A global crash in insect populations has found its way to Australia, with entomologists across the country reporting lower than average numbers of wild insects.

University of Sydney entomologist Dr. Cameron Webb said researchers around the world widely acknowledge that insect populations are in decline, but are at a loss to determine the cause.

“On one hand it might be the widespread use of insecticides, on the other hand it might be urbanisation and the fact that we’re eliminating some of the plants where it’s really critical that these insects complete their development,” Dr Webb said.

“Add in to the mix climate change and sea level rise and it’s incredibly difficult to predict exactly what it is. It’s left me dumbfounded.”

Entomologist and owner of the Australian Insect Farm, near Innisfail in far north Queensland, Jack Hasenpusch is usually able to collect swarms of wild insects at this time of year.

“I’ve been wondering for the last few years why some of the insects have been dropping off and put it down to lack of rainfall,” Mr. Hasenpusch said.

“This year has really taken the cake with the lack of insects, it’s left me dumbfounded, I can’t figure out what’s going on.”

Mr Hasenpusch said entomologists he had spoken to from Sydney, Brisbane, Perth and even as far away as New Caledonia and Italy all had similar stories.

The Australian Butterfly Sanctuary in Kuranda, west of Cairns, has had difficulty breeding the far north’s iconic Ulysses butterfly for more than two years.

“We’ve had [the problem] checked by scientists, the University of Queensland was involved, Biosecurity Queensland was involved but so far we haven’t found anything unusual in the bodies [of caterpillars] that didn’t survive,” said breeding laboratory supervisor Tina Kupke.

“We’ve had some short successes but always failed in the second generation.”

Ms. Lupke said the problem was not confined to far north Queensland, or even Australia. “Some of our pupae go overseas from some of our breeders here and they’ve all had the same problem,” she said. “And the Melbourne Zoo has been trying for quite a while with the same problems.”

Limited lifecycle prefaces population plummet

Dr. Webb, who primarily researches mosquitoes, said numbers were also in decline across New South Wales this year, which was indicative of the situation in other insect populations.

“We’ve had a really strange summer; it’s been very dry, sometimes it’s been brutally hot but sometimes it’s been cooler than average,” he said.

“Mosquito populations, much like a lot of other insects, rely on the combination of water, humidity and temperature to complete their lifecycle. When you mix around any one of those three components you can really change the local population dynamics.”

All this reminds me of a much more detailed study showing a dramatic insect population decline in Germany over a much longer time period:

• Gretchen Vogel, Where have all the insects gone?, Science, 10 May 2017.

I’ll just quote a bit of this article:

Now, a new set of long-term data is coming to light, this time from a dedicated group of mostly amateur entomologists who have tracked insect abundance at more than 100 nature reserves in western Europe since the 1980s.

Over that time the group, the Krefeld Entomological Society, has seen the yearly insect catches fluctuate, as expected. But in 2013 they spotted something alarming. When they returned to one of their earliest trapping sites from 1989, the total mass of their catch had fallen by nearly 80%. Perhaps it was a particularly bad year, they thought, so they set up the traps again in 2014. The numbers were just as low. Through more direct comparisons, the group—which had preserved thousands of samples over 3 decades—found dramatic declines across more than a dozen other sites.

It also mentions a similar phenomenon in Scotland:

Since 1968, scientists at Rothamsted Research, an agricultural research center in Harpenden, U.K., have operated a system of suction traps—12-meter-long suction tubes pointing skyward. Set up in fields to monitor agricultural pests, the traps capture all manner of insects that happen to fly over them; they are “effectively upside-down Hoovers running 24/7, continually sampling the air for migrating insects,” says James Bell, who heads the Rothamsted Insect Survey.

Between 1970 and 2002, the biomass caught in the traps in southern England did not decline significantly. Catches in southern Scotland, however, declined by more than two-thirds during the same period. Bell notes that overall numbers in Scotland were much higher at the start of the study. “It might be that much of the [insect] abundance in southern England had already been lost” by 1970, he says, after the dramatic postwar changes in agriculture and land use.

Here’s the actual research paper:

• Caspar A. Hallmann, Martin Sorg, Eelke Jongejans, Henk Siepel, Nick Hofland, Heinz Schwan, Werner Stenmans, Andreas Müller, Hubert Sumser, Thomas Hörren, Dave Goulson and Hans de Kroon, More than 75 percent decline over 27 years in total flying insect biomass in protected areas, PLOS One, 18 October 2017.

Abstract. Global declines in insects have sparked wide interest among scientists, politicians, and the general public. Loss of insect diversity and abundance is expected to provoke cascading effects on food webs and to jeopardize ecosystem services. Our understanding of the extent and underlying causes of this decline is based on the abundance of single species or taxonomic groups only, rather than changes in insect biomass which is more relevant for ecological functioning. Here, we used a standardized protocol to measure total insect biomass using Malaise traps, deployed over 27 years in 63 nature protection areas in Germany (96 unique location-year combinations) to infer on the status and trend of local entomofauna. Our analysis estimates a seasonal decline of 76%, and mid-summer decline of 82% in flying insect biomass over the 27 years of study. We show that this decline is apparent regardless of habitat type, while changes in weather, land use, and habitat characteristics cannot explain this overall decline. This yet unrecognized loss of insect biomass must be taken into account in evaluating declines in abundance of species depending on insects as a food source, and ecosystem functioning in the European landscape.

It seems we are heading into strange times.

5 Responses to Insect Population Crash

  1. insecticides have become extremely potent and property many miles away from sprayed fields are now deplete of anything that moves … I grew up in the countryside of upstate New York and can attest to the total disappearance of almost all species of insect … this area has become depopulated due to globalization and so human touch has actually become much more light so the insect depletion is not due to loss of habitat if anything wilderness has expanded … not only farmers field are getting sprayed, urban areas like nyc are heavily sprayed to tamp down West Nile Virus and the like … flying insects are gone from nyc as well … see some details for one such vector … to quote : Neonicotinoids are a group of pesticides that can be applied as seed coatings and are designed to protect crops such as oilseed rape (also known as canola), but were banned by the EU in 2013 due to concerns regarding their impact on bee health. The U.S. Environmental Protection Agency has issued a registration review for four neonicotinoids which is expected to be completed in 2018
    Country-specific effects of neonicotinoid pesticides on honey bees and wild bees
    http://science.sciencemag.org/content/356/6345/1393

  2. or maybe not…

    “At this stage, reports of insect population declines in Australia are only anecdotal.”

    umm… then use of the word “crash” in the alarmist repost headline is a bit hyperbolic don’t you think? (I know, you also reference the Deutschland study, but there you have the quote “Though observations about splattered bugs aren’t scientific…”.

    Could it be natural variation? (vs. assuming / insinuating the “human caused” arguments). What is the “natural” level of variation – the statistical periodic swings used as the basis for comparison? (Kyr data please, akin to ice cores that show we are at 40k to 100k yr peak temp cycles in Natural global warming over millions of years)

    Measuring insect populations in/around agriculture crops will guarantee human caused causation swings in BOTH directions. That may be unavoidable globally today, so care in making correlation vs. causation arguments are needed.

    “mix climate change and sea level rise “… sea level rise? With even the most extreme measures of rise being posited, what would be the causation logic for the limited real rise today? (DUMBfounded is right)

    The article seems to be making a “we need to study this” argument – that is great, keep studying it. But honesty (vs. alarmism) is better for making funding arguments for science in the long run. It keeps the pressure off for inserting statistical bias in causation arguments later.

    • John Baez says:

      J. Gregory wrote:

      umm… then use of the word “crash” in the alarmist repost headline is a bit hyperbolic don’t you think? (I know, you also reference the Deutschland study, but there you have the quote “Though observations about splattered bugs aren’t scientific…”.)

      The German study does not rely on observations of splattered bugs on windshields. As the article explains, people in Germany have been tracking insect abundances at about 100 sites since the 1980s, and they’ve dropped over 75%. I should have included a link to the actual research paper, and I will now, but here it is:

      • Caspar A. Hallmann, Martin Sorg, Eelke Jongejans, Henk Siepel, Nick Hofland, Heinz Schwan, Werner Stenmans, Andreas Müller, Hubert Sumser, Thomas Hörren, Dave Goulson and Hans de Kroon, More than 75 percent decline over 27 years in total flying insect biomass in protected areas, PLOS One, 18 October 2017.

      Abstract. Global declines in insects have sparked wide interest among scientists, politicians, and the general public. Loss of insect diversity and abundance is expected to provoke cascading effects on food webs and to jeopardize ecosystem services. Our understanding of the extent and underlying causes of this decline is based on the abundance of single species or taxonomic groups only, rather than changes in insect biomass which is more relevant for ecological functioning. Here, we used a standardized protocol to measure total insect biomass using Malaise traps, deployed over 27 years in 63 nature protection areas in Germany (96 unique location-year combinations) to infer on the status and trend of local entomofauna. Our analysis estimates a seasonal decline of 76%, and mid-summer decline of 82% in flying insect biomass over the 27 years of study. We show that this decline is apparent regardless of habitat type, while changes in weather, land use, and habitat characteristics cannot explain this overall decline. This yet unrecognized loss of insect biomass must be taken into account in evaluating declines in abundance of species depending on insects as a food source, and ecosystem functioning in the European landscape.

      This is an insect population crash. The question is whether something similar is occurring in Australia. Without systematic monitoring of insect populations, it’s hard to get any evidence other than anecdotal evidence. As the first article I quoted says:

      At this stage, reports of insect population declines in Australia are only anecdotal. And, without formal scientific research into the phenomena, Dr Webb said it was difficult to make accurate predictions or assessments about insect numbers. On the other hand, he said, it is important to listen to the entomologists, ecologists and researchers who are in the field on a regular basis.

      “You get a feel for what the general insect populations are like when you’re doing a lot of field work,” he said. “I don’t study cicadas, but I know what cicada numbers are like from year to year because I’m out and about in my local wetlands. “When experts are relaying this kind of information it is something that we need to turn our mind to and think about what could be going on, and more importantly how do we work out if this is actually happening and what we do about it.”

  3. “Where red legged earth mites were once regularly controlled in early crops, this pest is no longer a problem. Insect numbers have increased 600% with the changed management and have had a 125% increase in diversity. I believe it is both this diversity in species (spiders and beneficials) that is controlling the red legged earth mites, as well as the change in nutrient availability to the crop. The more balanced nutrition approach will mean a healthier, more robust plant which is more naturally resistant (and less attractive) to insect attack.”

    Pasture Cropping

    This was actually started by Colin Seis in Australia. It’s really a subset of what is today called Carbon Farming. It’s slowing catching on in the US and could probably use a bit of support.

  4. domenico says:

    I am thinking that it could be useful to do dna sequencing of some different species of insects in different years, so that the chemical, or environmental, cause could be found (maybe there is a collection for the different years).
    Insect counteract environmental variables with the evolution of the species, and specific genes could be discovered for a specific function, and also the cause of the reduction of the bees population could be found.

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