We are in the middle of a mass extinction. This alarming loss of biodiversity jeopardises our joy of life and endangers food production. No bugs, no fertile soil. The current EU pesticide regulation fails to protect non-target organisms.
In this campaign, we interview scientists, review new research and highlight the importance of arthropods. Our aim is to achieve the urgent protection of the natural abundance on which our lives depend. Here is an interview with entomologist Theo Zegers from the EIS Kenniscentrum (Knowledge Centre) in the Netherlands.
Watch the full Interview with entomologist Theo Zeegers
What is the focus of your work?
Theo Zeegers: I study pollinators, more specific bees and hoverflies and the other one is studies on trends of numbers or biomass of insects. In the focus of my attention is trends of pollinators because it combines both branches so we are doing a lot of field studies. So at my institute we are field ecologists. and I think it's clear at least to me that if you want to make assumptions or statements on causality between for instance pesticides and insects you'll have to study it in laboratory. So I will try to refrain from any causal statements on that matter but given my field experience I'm very worried about influence of pesticides on especially my type of insects what I'm seeing we can elaborate on this but it's a correlation it's not a causality just to be very clear on that matter.
What are arthropods?
As the name suggests, arthropods are animals which have limbs which are segmented and generally speaking, in most cases the body is segmented as well. So to give you the four main examples, spiders are arthropods, insects are arthropods, crustaceans and millipedes are arthropods. There are many more, but these are the four main groups and of these four insects are by far the most numerous and most species-rich group of animals in Europe and on our planet, especially terrestrial of course. So arthropods in general occur everywhere on the planet and insects more specifically occur everywhere on the planet except for in our oceans or in our seas.
Why are they important for ecosystems?
So you can find them from near the top of Mount Everest to Monaco and all in between. Only by their sheer number and by the sheer diversity. So what is an ecosystem would be the main question to return. If you say an ecosystem is a bunch of organisms interacting with each other and 80% of these animal organisms are insects or arthropods, then they constitute 80% of the ecosystem. So, of course, fungi are also very important. They're very numerous and very underestimated. We sometimes forget, but if you are looking at animals, then arthropods are by far the main group and they play every role you can imagine. There are herbivores, carnivores, parasitoids, blood sucking whatever you can imagine exists. So that makes them the heart, the liver and the kidneys of an ecosystem.
What can you tell us about the insect decline?
My first task was to start on with these studies and then I was working for a month and Caspar Hallmann presented the famous German study on decline of insects in Germany. That was for us a total game changer. So we repeated this study in the Netherlands with similar results. Caspar Hallmann is from the Radboud Nijmegen University and I'm cooperating a lot still with this University on this kind of studies. So everywhere we look, we find over the last 40 years typically a decline of 80% of the number of insects present. I'm talking about only western Europe and a decline of 30 to 50% of the number of species is sometimes reported, depending on which study you're looking at. So it's always either terrible or very terrible. Those are the two options we find.
There is some bias to open landscapes and forests are less studied, although we have a very good study in a forest. So maybe exceptions can be found in some habitat or whatever, but generally speaking this is the broad picture. So this tells me that there is something globally or at least on a very large scale going on because if it would be bad management of one nature reserve or bad management of one farmer, you could not explain a general decline all over the Netherlands and Germany for very different types of insects for very different localities.
There must be general principles causing this strong decline. So all entomologists, generally speaking, believe there are four main causes. Which is nitrogen because nitrogen changes our grasses and our trees and our woods and whatever. Pesticides, that's what we're talking about. Intensification of the use of the land, especially also by agriculture. The fourth one is the impact of climate change on our insect population in the Netherlands or the species present in the Netherlands, is huge.
So we are seeing, in extremely rapid tempo the number of southern species increase and the number of northern species decrease. Species which in my youth could not be found north of Paris are currently already present in the Netherlands for 10 years. Now this is tremendous rapidly. It's a different topic. But we also are concerned at least and we know in some cases like nitrogen and drought that they interact. So they are both generally bad for insects in our climate but the combined effect is bigger than the separate effects of both.
What role do pesticides play?
Pesticides have been underestimated by me in the past. We were looking at nitrogen a lot. and then I did this spring this study on extinction rates of hoverflies and bees in the Netherlands and we found for bees a more or less steady extinction rate from over the last 70 years. And for hoverflies, there was an enormous change in decline speed around 1990. This was statistically significant, which is already very nice with such poor data.
So if you ask an entomologist what happened in 1990, they will say introduction of neonicotinoids. So given that study I'm starting to be much more worried about the effects of pesticides in general and neonics, more in particular. I've made this statement before: there is no causal proof but the correlation is obvious and nobody has provided an alternative explanation for what's going on here.
The larval biology of my hoverflies is completely different from the larval biology of bees. As adult they have the same biology more or less, but the larvae are completely different.
In hoverflies, there are four main types of larvae and the type which declines the fastest predatory larvae. They feed on aphids and so I'm surprised that nobody has made this observation before. I think if you are worried about influence of pesticides, you should be worried about the influence of pesticides on your predators because the poison accumulates at higher trophic levels, as ecologists say and this is what we have learned from Rachel Carson. We know this for 50 years and now the second time it seems to happen and we miss it. So if you look at the animals which are used for these studies to be approved for the European market they use herbivorous animals to study the impact of these pesticides. Nobody's talking about carnivores. One hoverfly larvae eats 100 or several hundreds aphids in its lifetime. So, of course, it makes sense that these pesticides do not kill the aphids but they do kill the hoverfly larvae. It's not proven yet but you can imagine it can be true.
What would it lead to?
It makes me very depressed, for starters. So, when a journalist asks this question, I always say, what do you think about a world without bumblebees. What does your nephew think about the world without bumblebees? And they always say, yeah, okay, but it's exaggerated. You see bumblebees. Half of the number of 30 years ago. So, yes, it's demagogic to say, what's the world without bumblebees? But it's only 50% because we lost the other 50% already. So, what we're going to do? Are we going to sit on our hands to see what's happening or are we going to deal with the problem? I'm much less interested in direct usefulness for farmers or people or cows or whatever. I think the ecosystem has a value of its own and it also should be relevant to humans because they are part of it.
Is a threat to food production a good argument to protect pollinators?
If you're looking, for instance, at agriculture and pollination, a Dutch TV show asked a very good question. It made this very good observation: Our pollinators are declining but our apples and our cherries are not declining. So what's happening there? How can it be? Because if pollinators are so important for pollination of fruit trees, it should have an effect. And the answer is: our fruits are pollinated by commercial reared honeybees and bumblebees. So you can make industrial pollination by just asking Koppert to raise these bumblebees. That has all kinds of disadvantages, but from an agricultural point of view it's totally okay. So the concept of ‘pollinators are very important for our agriculture’ I'm always saying be very careful with this argument. Once somebody convinces or shows that we can have pollination without wild pollinators, your argument is blunt.
What should change in pesticide assessment?
We have had the case of imidacloprid which was admitted to the market in 1999 and was banned in 2018. So all this time the substance didn't change. So we can say now, with the current knowledge, that it was admitted to the market for the wrong reasons. The assessment at the time has been overturned by the assessment in 2018. Now I think it's beyond reasonable doubt that this is still happening with new substances that the admission to the market is not critically enough evaluated.
So I cannot pinpoint one example but it's clear that there is a tendency to admit it to the market, and it should be vice versa. We don't admit it to the market unless proven safe. So this, of course, is a different way of thinking. This would be a game changer and if you don't do that ….. The trouble is it has taken scientists 10 years to disprove the safety of imidacloprid and now they have done it and the industry will come with the next substance and it will again take 10 years to disprove the safety of this product and so this is an ongoing story. I don't have to explain this to you , you know what has happened. So the only way to change it is to say we don't admit it unless BAYER proves it's safe.
What do you think of the ‘recovery’ concept?
If you flood a meadow and once the meadow will return because the water will disappear. But that's not what is happening. There's a permanent flood, there's a permanent influx of these pesticides. better as me that made this rate has proven already the presence of many pesticides deep in our nature reserves.
So if it was a one incident like the gold mine in the Tisza River in Hungary, that might be true but it's not the case. It's the other way around. Henk Siepel who is a Professor at Radboud University and one of the co-authors of the famous Hallmann paper from 2017 said the first time he read the draft of the paper he thought this can't be true because if there is one group of animals which is robust on this planet it is insects.
So yes, if they got hit and they go down, they have a large reproduction strategy. So they can become numerous in two to three years, depending on the species, of course. So they are very robust but if you knock them down and you keep knocking, they stay down. That's what's happening. You need to stop these four stressors to give them a chance to recover. Yes, they can recover if you stop stressing them.
Do you have any advice for the regulators?
I don't think they are ready to change their basal attitude so maybe they will change some minor details but that's not the solution to this problem. If you look at their response on the court order they welcome this court order because they can learn from it's laughable. It's completely window dressing and with these managers there, it will keep being window dressing. If you are spraying pesticides they don't stay on your field but will evaporate to adjacent fields and even further. All these arguments have been made and all these arguments are from a content point of view, solid but it doesn't convince them. So then you need to convince them either by public opinion or by court or both. What you can learn from history from these processes is that when the minister is saying the market should solve the problem themselves in 90% of the cases, it doesn't happen. Lead got out of our petrol because of legislation, finally, after 30 years of debate. The market is saying it can't be done. And once you forbid it, they will find an alternative for the problem in a year's time. But if you don't force them to find the alternative, they won't invest in finding this alternative.
Conclusion
We have a huge system in the Netherlands which measures and predicts nitrogen deposition but as far as I know, no government is measuring pesticide levels. It's totally absurd.
