Do neonicotinoids harm organisms other than insects?

Neonicotinoids accumulate in sufficient concentrations to threaten organisms other than bumblebees, new research suggests...

The threat posed to bees by neonicotinoid insecticides ‘may be just the tip of the iceberg’, according to a new study published in the Journal of Applied Ecology. Research conducted by the University of Sussex’s Professor Dave Goulson reveals that soil organisms, aquatic life and farmland birds might also be harmed by these pesticides.

The study is based upon information taken from a diverse range of sources, including that provided by the agrochemical industry’s own research. Professor Goulson found that if used regularly, neonicotinoids accumulate in soil at concentrations far higher than those required to kill bees.

Neonicotinoids are predominantly applied as seed dressings. By coating seeds prior to germination – as opposed to spraying crops at a later date – this approach is intended to minimise the overspill of pesticides into unintended areas.

However, Professor Goulson points out that the reverse is true. Because neonicotinoids are soluble in water, over 90 per cent of their active ingredient is transferred from seeds to the soil. When the pesticides leach into groundwater, they can persist for years. Moreover, if neonicotinoids are applied by farmers on a regular basis, high concentrations of toxins can accumulate over sustained periods of time.

In April 2013, the European Commission introduced a two-year moratorium on the use of three common neonicotinoids in response to growing concerns over pronounced declines in bumblebee populations.

In the following interview with ScienceOmega.com, Professor Goulson, head of the University of Sussex’s Goulson Lab, discusses neonicotinoids’ potential to harm a wide range of organisms, and questions whether these insecticides should be permitted to play any role in modern agriculture…

Could I begin by asking a fairly rudimentary question: what is a neonicotinoid?
Neonicotinoids comprise a class of insecticides invented in the late 1980s and introduced in the early 1990s. Whilst they are chemically related to nicotine – hence the name – they are, in fact, synthetic molecules. Neonicotinoids are neurotoxins that are particularly potent against insects. They attack an organism’s nervous system, blocking open nerve receptors so that they fire continually. Neonicotinoids paralyse and kill insects pretty quickly.

How do these insecticides accumulate in soil?
Seed treatment – a relatively new technique – was devised as a way to target crops. The old-fashioned method of spraying, for example, allows pesticides to blow around in the wind. This new method, therefore, was seen as a big improvement because people assumed that a lot more of the active ingredient would end up where it was supposed to be: in the crop itself.

Ironically, it turns out that a lower proportion of the active ingredient ends up in the crop than if you were to spray. This actually isn’t that surprising when you think about it because neonicotinoids are water soluble. In Western Europe, crops tend to be sown in October and not much happens until germination. In the meantime, any water-soluble chemicals sitting on the outsides of seeds are washed into the soil. Evidence shows that in comparison to the quantity of insecticide that starts off on the seed, very little gets into the resulting crop. Up to 98 per cent of the active ingredient is lost to soil and water.

And is it the case that in these concentrations, neonicotinoids might endanger organisms other than bumblebees?
We know that neonicotinoids wash into the soil, and when they accumulate, they don’t break down quickly. As our study points out, it is common for these insecticides to have half lives in excess of 1000 days. Even after approximately three years, half of the active ingredient remains. Many farmers apply neonicotinoids on an annual basis. This means that about 80 per cent of the neonicotinoid that was applied in year one will still be present when reapplication takes place in year two, and so on. Consequently, toxin levels will rise steadily, year in, year out.

This clearly raises concerns in relation to the range of affected wildlife. There is every reason to suspect that neonicotinoids pose a threat that extends far beyond bumblebees. Farmland soils are accumulating higher and higher levels of – what are essentially – highly toxic compounds, and this is very likely to harm wildlife. Earlier this month, the RSPB-led ‘State of Nature’ report revealed that 60 per cent of species in the UK are in decline. Approximately 30 per cent are declining particularly rapidly. Now, I’m not suggesting that pesticides are the sole cause of this decline, but they certainly aren’t helping matters.

In light of these problems, I understand that you're doubtful of the efficacy of the two-year moratorium on neonicotinoid use. What measures would you like to see in order to protect wildlife against potential harm?
Personally, I think we need to weigh up our food-related needs against our need to protect the environment. Any form of agriculture – even organic farming – is essentially harmful to biodiversity. If the country were covered exclusively in forests and flower-rich meadows, there would be a lot more wildlife. Unfortunately, we wouldn’t have any food.

It’s a question of striking the right balance between these two extremes. It seems to me that this particular group of chemicals falls outside of that balance. The benefits that neonicotinoids provide are dubious. In fact, evidence suggests that in some crops, they achieve nothing whatsoever. I haven’t heard a convincing argument to demonstrate that we need neonicotinoids, but I’ve seen plenty of compelling evidence to show that they are damaging our environment. To me, it seems pretty clear that these insecticides do a lot of harm but offer little, if any, genuine benefit. In my opinion, therefore, neonicotinoids have no place within farming.

If you are correct and neonicotinoids aren’t effective, why is the agrochemical industry so keen for farmers to keep using them? Is this purely about profit or is it due to a lack of proper understanding?
That’s an interesting question. I’m a scientist so I can’t tell you exactly why agrochemical companies do what they do. However, my best guess would be that their allegiance to neonicotinoids is largely about profit. This industry has succeeded in persuading large numbers of farmers to use these insecticides on a routine basis, and on most of their crops. There are plenty of other companies that sell us things that aren’t terribly useful; the cosmetics industry, for example, has been largely built upon this model.

Unfortunately, we have a situation whereby the agronomic advice that farmers receive is almost entirely provided by people who sell pesticides. There are very few independent advisers for farmers. If doctors were paid solely on commission from pharmaceutical companies, you might not be entirely trusting of their advice. Well, farmers are being advised by individuals who make most of their money selling pesticides, so it should come as no surprise to hear that these people are advising them to buy pesticides.

It seems to me that we have a system that is fundamentally flawed. It has been set up to oversubscribe agricultural chemicals, and this is terrible for our environment.


For further information about bumblebee ecology and conservation, check out the Goulson Lab's webpage...