Neonicotinoids & our feathered friends

Neonicotinoids are a controversial insecticide that you may have come across in the news. Since entering the market in the 1990’s, they have become one of the most widely used classes of insecticides worldwide. Upon introduction, they were considered a more environmentally-responsible alternative to traditional pesticides, given that rather than being showered on entire fields, neonicotinoids could be used to treat specific seeds, as their systemic properties enable them to be incorporated into a growing plant’s tissues.

However, in recent years, concern has been raised around the negative impacts of neonicotinoids on wildlife. Their deleterious effects on insects (such as bees) are widely known and a popular area of research, however there is far less literature on the impacts of neonicotinoids on birds, though studies now show that birds are also being harmed, with farmland-dependent birds experiencing population declines. This is alarming, as it threatens global biodiversity and the critical ecosystem services these animals provide, many of which human society and economy relies upon.

This blog reviews the existing literature on the impacts of neonicotinoids on birds, with the purpose of highlighting research trends and controversies. Buckle up!

Neonicotinoids are typically applied as seed treatments to oilseed and grain crops, however they have been reported to drift into aquatic systems and untreated areas, with contamination of non-target areas and harm to non-target organisms reported in several European and North American countries. In Europe, farmland birds have experienced steep population declines since the 1990’s, with agricultural pesticides cited as a major reason.

The effects of neonicotinoids on birds are both direct and indirect. Direct exposure occurs through ingestion of treated seeds, contamination of water or insect prey, dermal exposure to sprays or residues, and spray inhalation. In terms of indirect effects, significant insect declines in areas with high concentrations of neonicotinoid-contaminated waterbodies correlate with a decline in insect-eating birds, suggesting neonicotinoids also harm birds through the depletion of food resources. While the highest risk is for insectivores, granivores (seed-eaters), and pollinators, high-level species like birds of prey are also impacted by neonicotinoids.

The primary focus of neonicotinoid research on birds has been the ingestion of treated seeds, finding that even a couple seeds have the ability to produce sublethal and lethal effects on small birds. Sub-lethal effects may include the disruption of cognitive and motor functions, altering neurophysiological and behavioural processes such as thermoregulation and appetite. Other effects include changes to immunity and chronic effects on growth, development, and reproduction. Finally, neonicotinoids impact migratory ability and the timing of breeding; given that this can lead to fewer and weaker offspring, it has the potential to have population-level consequences.

With the growing body of literature indicating neonicotinoids negatively impact wildlife, many environmental groups advocate for neonicotinoid bans, with the EU banning the use of imidacloprid, clothianidin, and thiamethoxam in fields in 2018. However, this is an issue of hot debate, with pesticide companies and farmers insisting neonicotinoids are not toxic to wildlife when properly administered.

Given the agricultural industry’s reliance on neonicotinoids, a ban would undoubtedly have social and economic implications. Firstly, banning neonicotinoids begs the question, what would replace them? Farmers insist that without neonicotinoids, the threat of pests can cause complete crop loss as pests have developed resistance to other control methods. However, in a 2019 assessment of neonicotinoid alternatives, an effective alternative was available in 96% of case studies, arguing alternatives exist and should be promoted. Examples of alternatives include biological control, altered farming practices, use of semiochemicals, physical barriers, and genetic modification for pest-resistance.

Opponents of bans also question how we can balance environmental advocacy with economic concerns and food security, specifically if crop yields become threatened. Field experiments on maize in Indiana found no benefit to crop yields when using neonicotinoids, and  the same has been found with oilseed rape in Europe and soybeans in America. It’s likely that the current concentrations of seed treatments being used in North America exceed the need, as the threat of target pests may be less than feared. However, there is some conflicting data on this. One study reported that the UK has experienced significant crop losses and decreased yields in oilseed rape without neonicotinoid application, suggesting the success of crops in the absence of neonicotinoids depends upon their location, species, pests, and various other factors.

The issue of banning neonicotinoids is complex, as it involves the conflicting demands and objectives of environmentalists, farmers, industry, government, and the public. At this intersection of environmental, social, and economic concerns, care must be taken to consider all three imperatives and strive for solutions that support them all, as sustainable solutions require effective integration.

In conclusion, recent studies indicate neonicotinoids are capable of having significant negative effects on avian health, behavior, and survival. Although there is disagreement as to the scale of these impacts, and no shortage of controversy, the majority of research acknowledges neonicotinoids are capable of having toxic effects on birds and call for more data to bolster the current collection of literature on the topic.

Future recommendations include reducing risk to non-target organisms by limiting neonicotinoid use to levels that more realistically reflect pest pressure, and only resorting to them when no viable alternatives are available; providing government aid to assist in a transition to more environmentally-responsible methods, and compensating farmers for losses during this transition; expanding neonicotinoid ecotoxicology tests to include more vertebrate wildlife and evaluating both direct and indirect effects; and taking the risk of cascade effects on ecosystems into consideration in legislation through moratoriums or bans, if scientifically justified.

Although the issue of keeping or banning neonicotinoids is controversial and the latter may be met with resistance from farmers protecting their economic interests, it may be the case that we have even more to lose in a world without the birds and the bees.

References

  • Addy-Orduna, L., Cazenave, J., & Mateo, R. (2022). Avoidance of neonicotinoid-treated seeds and cotyledons by captive eared doves (Zenaida auriculata, Columbidae). Environmental Pollution, 304. https://doi.org/10.1016/j.envpol.2022.119237.

  • Dewar, A.M. (2016). The adverse impact of the neonicotinoid seed treatment ban on crop protection in oilseed rape in the United Kingdom. Pest Management Science, 73(7), 1305-1309. https://doi.org/10.1002/ps.4511

  • Eng, M.L., Stutchbury, B.J.M., & Morrissey, C.A. (2019). A neonicotinoid insecticide reduces fueling and delays migration in songbirds. Science, 365(6458), 1177-1180. https://doi.org/10.1126/science.aaw9419

  • Gibbons, D., Morrissey, C., & Mineau, P. (2015). A review of the direct and indirect effects of neonicotinoids and fipronil on vertebrate wildlife. Environmental Science and Pollution Research, 22, 103–118. https://doi.org/10.1007/s11356-014-3180-5

  • Hallmann, C.A., Foppen, R.P.B., van Turnhout, C.A.M., de Kroon, H., & Jongejans, E. (2014). Declines in insectivorous birds are associated with high neonicotinoid concentrations. Nature, 511, 341–343. https://doi.org/10.1038/nature13531

  • Humann-Guilleminot, S., Laurent, S., Bize, P., Roulin, A., Glauser, G., & Helfenstein, F. (2021). Contamination by neonicotinoid insecticides in barn owls (Tyto alba) and Alpine swifts (Tachymarptis melba). Science of The Total Environment, 785, 147403. https://doi.org/10.1016/j.scitotenv.2021.147403

  • Jactel, H., Verheggen, F., Thiéry, D., Escobar-Gutiérrez, A.J., Gachet, E., & Desneux, N. (2019). Alternatives to neonicotinoids. Environment International, 129, 423-429. https://doi.org/10.1016/j.envint.2019.04.045

  • Krupke, C.H., Holland, J.D., Long, E.Y., & Eitzer, B.D. (2017). Planting of neonicotinoid-treated maize poses risks for honey bees and other non-target organisms over a wide area without consistent crop yield benefit. Journal of Applied Ecology, 54(5), 1449-1458. https://doi.org/10.1111/1365-2664.12924

  • Landis, W.G., Sofield, R.M., & Yu, M. (2017). Chapter 3: Overview of Toxicity Test Methods. In Introduction to environmental toxicology: Molecular substructures to ecological landscapes (5th ed., pp. 35-77). CRC Press.

  • Lennon, R.J., Isaac, N.J.B., Shore, R.F., Peach, W.J., Dunn, J.C., Pereira, M.G., Arnold, K.E., Garthwaite, D. & Brown, C.D. (2019). Using long-term datasets to assess the impacts of dietary exposure to neonicotinoids on farmland bird populations in England. PLOS One, 14(10). https://doi.org/10.1371/journal.pone.0223093

  • Lundin, O. (2021). Consequences of the neonicotinoid seed treatment ban on oilseed rape production: What can be learnt from the Swedish experience? Pest Management Science, 77(9), 3815-3819. https://doi.org/10.1002/ps.6361

  • Stokstad, E. (2013). Pesticides under fire for risks to pollinators. Science, 340(6133), 674-676. http://doi.org/10.1126/science.340.6133.674

  • Turaga, U., Peper, S.T., Dunham, N.R., Kumar, N., Kistler, W., Almas, S., Presley, S.M., & Kendall, R.J. (2015). A survey of neonicotinoid use and potential exposure to northern bobwhite (Colinus virginianus) and scaled quail (Callipepla squamata) in the Rolling Plains of Texas and Oklahoma. Environmental Toxicology and Chemistry, 35(6), 1511-1515. https://doi.org/10.1002/etc.3305

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