Disturbing the natural order – the case of neonicotinoid insecticides and farmland birds

Apus apus 01.jpg
A swift

 

One of my favourite nature writers is Mark Cocker who has the ability to capture a scene or an idea in a few hundred words. Despite his immense knowledge he never loses his sense of awe and with clever use of metaphor, his descriptions of nature leap in to life.

Here is Cocker writing about the interdependence of birds and insects:
“…… that vast efflorescence of insect life is integral to spring. After all, those swifts newly screaming over our village and the chorus that greets us at first light are little more than arthropods processed by avian digestive systems”.

Another favourite nature writer, Kenneth Allsop wrote, nearly fifty years ago, also about bird/insect interdependence. He took the example of a pair of dunnocks in the breeding season who consume more than 1000 insects each day just to maintain their chicks. Many of those insects, he pointed out, will be garden pests, “worth bearing in mind when irritated by bird damage to the green peas and apple buds”.

Despite this obvious dependence of bird life on insects, we still dump insecticides on to our gardens, parks and farmland with little real thought about the long term consequences.

One class of insecticide that has recently attracted scrutiny is the neonicotinoids. The neonicotinoids were introduced in the 1990s and are now very widely used to kill insect pests on a broad range of crops. In the UK, for example, a large proportion of the oil seed rape is grown using seed treated with neonicotinoids. One of the advantages of the neonicotinoids is their selectivity for invertebrates; in principle they have low toxicity towards vertebrates. There has, however, been increasing concern about effects of the neonicotinoids on non-target insects such as bees and the accumulation of the chemicals in soil and water courses with more general effects on invertebrates.

New worries about the neonicotinoids surfaced last week in a paper published in Nature by Hallmann and colleagues from Radboud University in the Netherlands. The Dutch group investigated whether these chemicals might be affecting the numbers of farmland birds indirectly by reducing the numbers of insects that these birds depend upon especially in the breeding season.

They took advantage of long-term monitoring schemes in the Netherlands to compare the average concentrations of one neonicotinoid (imidacloprid) in surface water between 2003 and 2009 with bird population trends over the same period. The comparison was made in different regions across the entire country and focussed on 15 species of common farmland bird that depend on invertebrates during the breeding season.

Yellow wagtail.jpg
Yellow wagtail (one of the farmland birds suffering a decline)

 

The comparison showed that in regions where concentrations of imidacloprid in surface water were higher, population growth rates of these insectivorous birds were lower or negative. Although superficially this suggests that imidacloprid has caused the decline in bird numbers, we first need to rule out alternative explanations for the apparent association.

Hallmann and colleagues consider two possible alternatives: first, the apparent effect of imidacloprid might actually reflect an ongoing decline in bird numbers that predated the introduction of this insecticide; second, the apparent imidacloprid effect might actually reflect changes in land use linked to agricultural intensification. They eliminate both of these alternatives.

Another possible confounding factor that the authors seem to have ignored is the effect of other pesticides. The Netherlands is a very intensively farmed country with more than 60% of land under cultivation. Many different chemicals are used to control pests including imidacloprid. It seems likely that areas with high imidacloprid use will be associated with high usage of other chemicals. Another Dutch group has analysed the large numbers of chemicals present in Dutch agriculture and shown that, in some regions, concentrations of imidacloprid are high enough to kill invertebrates but levels of other chemicals also exceed toxic doses. So, it could be imidacloprid that is leading to the decline in farmland birds or it could be a generally toxic environment. Either way, the conclusion is bleak and ought to make us reflect on the way we are producing our food.

Although the effects of imidacloprid described in this paper are open to interpretation, the evidence against the neonicotinoids continues to accumulate and some authors believe they are having widespread deleterious effects on the natural environment. George Monbiot, writing in the Guardian last week, called for a complete ban on the use of these insecticides.

The Center for Food Safety, a US-based non profit organisation, recently took a different approach to the neonicotinoid problem by asking how much the insecticides actually increase crop yield. Analysing 19 published studies, they found either inconsistent or no evidence that neonicotinoids increase yield. So, astonishingly, dumping neonicotinoids on farm crops has little discernable effect on productivity. Have we all been conned by the agrochemical companies?

 

[picture credits:  “Apus apus 01” by Paweł Kuźniar (Jojo_1, Jojo) – Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons.

Yellow wagtail” by Andreas TrepteOwn work. Licensed under CC BY-SA 2.5 via Wikimedia Commons.]

15 thoughts on “Disturbing the natural order – the case of neonicotinoid insecticides and farmland birds”

  1. I like that you question whether a direct causal link between neonics and declining bird population has been proven, positing the theory that it could just be a generally toxic environment caused by other insecticides. So then why revert back to “the evidence against the neonicotinoids continues to accumulate”? Not necessarily according to your summary of the conclusions of this study….

    To bring it into the ‘citizen science’ realm, we have had to start closing our conservatory which is experiencing its seasonal assault from the ant population upon which I visit Raid showers. But after we saw baby robins in the conservatory pecking at bugs on the floor, we now observe a closed-door policy….

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    1. Thanks for your comment, you immediately spotted the flaw in my logic and I appreciate that – I have amended that section accordingly.

      Are these flying ants as I recently saw some down here?

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      1. Just a bit of grammatical tinkering required, it seems.

        I believe flying is the way they would go based on past years. As long as they stay on their side of the glass window they can do anything they want. But once they invade my territory…

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  2. Interesting that I read your post just minutes after seeing a report on the effects of Roundup in US agriculture. The result has been superweeds and a fall in production for many farmers. Yet it is still used… I fear the answer to your final question is far too clear.

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  3. So interesting but I think it is fairly obvious that in trying to alter the natural balance of an environment will only cause problems in another area. Living in a rural, agricultural area of France I have observed far fewer garden birds compared with urban Surrey for example. It is only a very poor circumstantial observation but as our trees, bushes and flowers increase we are noticing more birds in the garden. That could be put down completely to shelter and food but the area supports much less small bird life than I would have expected.
    My two concerns with banning the use of neonicotinoids is that 1. It will not be respected in France and 2. Will they be replaced with something worse? Amelia

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  4. I would imagine that you have large areas of monoculture around you and that on it’s own can’t be good for wildlife.
    I am not necessarily in favour of a complete ban for the reasons you mention. I would like to get people to think about whether the neonics are actually increasing yields because if they are not then farmers are wasting money and killing wildlife unecessarily.
    I would also like a return to Integrated Pest Management which, I believe, operates on a “treat when you need to” basis – I dont like the idea of treating everything with neonics from the outset whether you have a problem or not.
    Thanks for your thoughtful comments. Philip

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  5. It is such an interesting web we weave. And a web is a good way to imagine the effects on ALL that we touch. I like this update on neonics, but the problem is far more encompassing on so many creatures, even us in the end. I suspect one day it will finally dawn on people that 1. There are too many of us to live sustainably without doing harm to where we live, and 2. That this harm compounds exponentially.

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  6. Thanks for this post. The one issue with banning neonics is that the alternative has been potentially worse in terms of potential impacts on the wider biosphere. With the neonics ban came an increase in the use of older insecticides, mainly pyrethroids. About 240,000 litres of insecticide, mainly pyrethroid-based chemical, was applied to winter oilseed rape crops in England to combat actual, or predicted attacks of cabbage stem flea beetle, in the harvest year of 2014-15. In excess of 1.1m ha was estimated to have been sprayed against flea beetle, with 33,597kg of active substance used. This represented a 2.5-fold increase in the use of autumn insecticides in England to combat the threat of flea beetle, compared with 2013. Cypermethrin was used by 50% of growers, followed by lambda-cyhalothrin (40%) and pymetrozine (11%). To sustain the yields that farmers need to make a profit as well as meeting the demands of industry and consumers, some form of chemical control will continue to be used. Integrated Pest Management is common sense to a certain extent and with the price of sprays as it is when compared to income from crops most farmers are inadvertently going down this line. However, we need to generate a system whereby we can continue to boost production to feed an ever growing population (if the world can morally justify that increasing population) whilst at the same time ensuring biodiversity doesn’t continue to crash and pollinators die. Perhaps wishful thinking to achieve this but this must be the aim.

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  7. Thanks for your thoughtful comment, I apologise for my slow reply but I have been preocccupied with some other issues.
    I hadnt realised the extent to which pyrethroids had been used instead of neonics since the partial ban. Does this mean that when people say that the banning of neonics has not affected yields very much, they really mean the banning of neonics and replacement with pyrethroids?
    I dont really know what to think any more, it feels to me like farming has become too dependent on chemicals and that is what we should be moving away from. I personally dont want my food to imply the elimination of bees from the countryside.
    I would very much like to know how the finances work for farmers and how a less chemical world would look economically. I dont know the cost of the treatments used but I remember being appalled when I read how many chemicals were used and wondering what this implied for costs.
    The other issue is the persistence of the treatments used. It looks like the neonics last for quite a long time and with prophylactic use they build up in the soil. My understanding was that the pyrethroids dont hang around very long??

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