Experts

Current topics explained by RUG experts

Insects

The insect population is declining drastically. Natuurmonumenten recently published the numbers for two nature reserves in the Netherlands: over the past twenty years, more than half of the moth population has disappeared, and approximately three quarters of the ground beetle population. Is agriculture to blame?
By Jurgen Tiekstra / Translation by Sarah van Steenderen

Leo Beukeboom

Professor of evolutionary genetics

‘This is not actually a surprising development. Bugs aren’t cute and fluffy, so we tend to disregard them. We already know that the meadow bird population is declining every year, and now the same thing is happening to insects. There is a distinct connection between these two occurrences: the birds are in decline because there are fewer insects. The species diversity of bugs doesn’t matter to birds, but their numbers do. Insects are also crucial to plant pollination.

It’s been proven that the honey bees are dying because of neonicotinoids. Neonicotinoids are a pesticide that affects the nervous system. They have recently been banned by the EU. As far as I’m concerned, this is clearly what is affecting the other insects. I’m convinced that pesticides and the increase in agriculture are the main causes of the insect decline, although there are scientists who question this, because there has been no systematic research into it. Agriculture should really start taking nature into account. If it doesn’t, nature will suffer.

I don’t think the ban on neonicotinoids will have much of an effect; there are many more harmful pesticides that are being used. Take the DDT crisis, for example, when it was shown that this pesticide had a negative impact on birds’ egg shells and that it accumulated in organisms’ fatty tissue. But after the ban on DDT, other insecticides were introduced, which also had harmful side effects. We have to make the switch to organic pesticides. I’ve just returned from the first international conference on organic pest control in China. Organic pesticides still need much improvement. And the companies that make them are small potatoes compared to chemical giants such as Bayer and Dow and their powerful lobbyists.’

Dirk Strijker

Professor by special appointment of rural development

‘I am as concerned as everyone else. We need insects, because they are at the start of the food chain. But we don’t know why their populations are declining. Research has shown that they’re not doing well in the nature reserves. Spiteful scientists would point their fingers and say the reserves are poorly managed. But it’s much more problematic than that. Next, everyone starts blaming agriculture. One ecologist from Wageningen even said he was absolutely sure it was due to agriculture. He didn’t know why, because there was no time for research; something had to be done right now. That’s just insanity.

Sure, neonicotinoids are partially to blame. It’s a good thing that they’ve been banned. But agriculture is also blamed for other things: we keep impoldering in the Netherlands, which leads to fewer bugs; agricultural plots are increasingly bigger, and insects need places to rest when they’re flying somewhere. It’s possible that they can’t make it across a corn field of a few hundred hectares. These are all possible explanations. We just don’t know.

Even if we could say for certain that agriculture was to blame, we wouldn’t know which factors are responsible: whether it’s pesticides or herbicides, plot size, fertiliser, harvest times, or the water balance. I do think agriculture is partially responsible, but I don’t think it’s the only cause, and I also don’t know how we would go about changing agriculture. We just need to do more research. We especially need autonomous research rather than research that seeks to reach a certain conclusion. But that’s difficult: many ecologists and biologists have their own opinions on the matter. That makes it hard to have an objective discussion.’

Raymond Klaassen

Ecologist, studies nature-inclusive agriculture

‘Half to three quarters of insects has disappeared. That’s pretty bad. Moreover, that number is based on a measurement that was recently taken; before that, there may have been even more insects. So there is definitely something going on. Climate change may have played a role, of course. It’s really difficult to determine exactly how it’s affected the insects, however. We do know that insects are very temperature sensitive. And then there’s the issue of agricultural pesticides, as well as the overfertilisation and acidification of nature reserves.

Those last two are caused by the amount of fertiliser that is used in agriculture, which has increased a lot over the past few years. Some of this fertiliser leaks or is spread through the air. This leads to high concentrations of for instance nitrogen in nature reserves. It’s because of agriculture. All sorts of regulations have been introduced to try and limit the exhaust. Slurry, for example, or semi-liquid manure, is being injected these days.

Agriculture has undergone huge changes, and these nature reserves are relatively small. So it makes sense that they are so impacted by agriculture, although we’re not sure what exactly this impact entails. The fact that Natuurmonumenten is only pointing the finger at agriculture is a little shocking. I don’t think it’s wrong to say it, because agriculture probably does play a role, but I think they should have been more nuanced in their announcement.

I think we need to study the types of agriculture and how they each impact the insect populations. Should we focus on more organic agriculture, or on more nature-inclusive agriculture that uses fewer pesticides? That’s an interesting study.’

Nederlands