Neonicotinoids in flux: EU bans, UK reintroduction and the future of pollinator protection

Neonicotinoids are insecticides used to protect crops and promote higher yields. Directly harming non-target populations, however, their usage threatens biodiversity. This environmental brief summarises the key impacts and legislation surrounding neonicotinoid application today.

Background

Neonicotinoids are an example of systemic insecticides, meaning the uptake of the chemical is typically done via plant roots. In most usage instances, the chemical coats the crop seed before sowing commences to inhibit destructive species interfering with crops in their early stages of development1. Similar in composition to nicotine, neonicotinoids work by actively binding with nicotinic acetylcholine receptors, directly altering the functionality of the central nervous system in organisms. This reduces the ability of these organisms to hinder crop growth, in turn, promoting enhanced crop yields. The most commonly used neonicotinoids include imidacloprid, thiamethoxam and clothianidin.

Environmental pathways

Due to large-scale application of neonicotinoids within agriculture, a direct point source cannot be traced. This vast application gives way to a significant quantity of transportation pathways, allowing the chemical to freely encroach into other areas of the environment and ultimately, endanger non-target species. The ‘all-or-nothing’ characteristic of neonicotinoids enhances these unfavourable consequences, affecting a diverse range of organisms due to the ease of receptor binding. Only ~5% of the active ingredient found in neonicotinoids is captured by the crop during growth, leaving a substantial mass to be transported elsewhere2.

Movement of the compound away from the initial source is encouraged by the highly soluble (log Kow = 0.55 to 1.26; log Koc = 1.4−2.3) and persistent nature (half-lives of 4.7−40.3 days in water) of the chemical1. A common pathway of neonicotinoids is therefore via surface runoff from irrigated or flooded agricultural soils into nearby water sources. Leeching of the insecticide is another transportation pathway, leading to soil contamination with a half-life of up to 3 years, carrying the compound into the next round of crop growth. The pollination of crops grown with neonicotinoids by bee species enables an even wider movement of the chemical through the surrounding environment.

Damaging environmental effects

At face value, neonicotinoids overstimulate organisms’ nerve cells, with realistic field applications in laboratory tests concluding decreased foraging success, reduced navigational skills, and immune system suppression1. The complication is that this form of chemical exposure does not exclusively impact target species. Honeybees are one the most common non-target species to be directly impacted by the application of neonicotinoids (Figure 1), with colony collapse disorder (CCD) being one of the most felt impacts for the species – reducing food production elsewhere and, arguably, cancelling out the benefits of a yield-enhancing insecticide.

The adverse effects on non-target species are not confined to insects, with aquatic life subject to habitats infiltrated with neonicotinoid contaminated surface water runoff, leading to bioaccumulation of the chemical within organism tissue. Studies have also brought to light that some bird species are harmed through insecticide usage. Although this is most commonly through consumption of exposed insects, granivorous and frugivorous bird species also demonstrate similar behavioural traits to those infected via direct insect consumption, suggesting a wider exposure to pollution via contaminated soils, air, or water sources 3.

Governance and compliance measures

The regulation of neonicotinoid application depicts a critical contrast between the EU and UK’s positions. Regulation (EU) No 485/2013 restricted neonicotinoid usage across all EU member states for crops specifically attractive to bees, from January to June4. This was tightened in May of 2018 to ban all outdoor usage of the insecticides. This legislation applied to the UK, until Brexit in January 2020. The strict laws surrounding neonicotinoid usage were first overturned by the UK government in 2021, where use of the thiamethoxam-containing insecticide Cruiser SB was authorised to protect sugar beet crops5. Requests for further authorisation have been granted in subsequent years, with the latest approval in January 2024, prolonging usage for a further vegetative period.

Figure 1 summarises the application of neonicotinoids in the UK, highlighting a significant resurgence of almost 2,500 tonnes after the restrictions imposed by the EU were abolished. A drop in use of ~5,000 tonnes between 2018 and 2020 reflects the EU prohibition of the chemical compound. Those within the agricultural sector benefit largely from these relaxed restrictions, with enhanced yields promoting economic opportunity. Opposing environmentalist groups suggest that reintroduction prioritises short-term ts profits over environmental longevity and sustainability. The future legislative aspect of neonicotinoid application is uncertain. As summarised in Figure 2, the benefits of usage are somewhat reduced when the harmful environmental aspects cancel out the aim of food security. The election of a Labour government into parliament in July of 2024 offers a potential for change: their manifesto acknowledges the insecticide’s potential to damage the environment, and support for sustainable farming techniques with ‘less reliance on chemicals’ through integrated pest management4.

Conclusion

Neonicotinoids pose a health threat to non-target populations and, although limited, its use within agriculture in the UK creates tension between agricultural productivity and environmental safeguarding. Striking a balance between the two is imperative to the future of chemically assisted crop growth in the UK.

References

1. EFSA, EFSA Supporting Publications, 2021, 18(11). https://doi.org/10.2903/sp.efsa.2021.EN-6958

2. Hladik, M.A., Main, A.R. and Goulson, D., Environmental Science and Technology, 2018, 52(6) 3329. https://doi.org/10.1021/acs.est.7b06388

3. Molenaar, E., Viechtbauer, W., Van de Crommenacker, J. and Kingma, A.S Ecology Letters, 2024, 27(10). https://doi.org/10.1111/ele.14534

4. Parliamentary Office of Science and Technology, CDP-2024-0047, 2024. https://researchbriefings.files.parliament.uk/documents/CDP-2024-0047/CDP-2024-0047.pdf

5. Ridley, L., Parrish, G., Chantry, T., Richmond, A., MacArthur, R. and Garthwaite, D. (2022) Arable crops in the United Kingdom. https://pusstats.fera.co.uk/