New critters in the Netherlands – we’ll just have to get used to them

The Asian hornet, the false wolf spider, the pine processionary caterpillar, the American crayfish, the Mediterranean spinning hole (a species of ant): the Netherlands is teeming with new critters. “A lot is going on at the same time,” entomologist Daan Drukker notes. He works at EIS, a knowledge center for insects and other invertebrates. Some newcomers have been on the rise for some time, but Drukker notes that some species, such as the Asian hornet, are moving unusually fast. “We had better get used to the fact that we will encounter new species more often. Also in and around our house.”

This is mainly because two factors interact: due to rapid global warming, the habitat of animals from southern and central Europe is slowly shifting towards the Netherlands. And new animals regularly hitch a ride on freight and passenger transport, ballast water from ships and on exotic plants. “You can roughly say that climate change and globalization are the main causes,” says Drukker. For some species, the two reinforce each other: because winters have become milder here, species from generally warmer areas can survive here.

Terror ants and terror wasps

In the media, the new species are often referred to as ‘terror ants’,’Asian Terror Wasps‘, ‘false widow spiders’, which attack without provocation and can make people sick with their venom. Fear prevails. Is that right? Take the horned mason bee. This bee species has been present in the Netherlands for some time, it originally comes from Central Europe, and has been advancing strongly in recent years, both in terms of numbers and distribution. They also thrive because they like the many bee hotels that people set up to give the pollinating insects a helping hand. Hopeful: human actions apparently matter, and more bees means good news for the rest of nature.

But the consequences for ecosystems of a newcomer or an expanding species vary considerably. “Some new species can thrive here without causing damage,” says Drukker. For the climate movers from Southern Europe or the native species that are increasing in numbers, their natural enemies are gradually moving along, so that the population remains in balance. But this does not apply to animals that have suddenly been introduced from exotic places: they can suddenly gobble up here uninhibited.

Predatory insects

The Asian hornet, which can sting viciously, is an example of this. It was first seen in the Netherlands in 2017, after a first litter probably ended up in France with a shipload from Asia. In the Netherlands, the Asian hornet mainly lives under the major rivers, but is now also appearing in other provinces for the first time.

“They are predatory insects: one nest eats about eleven kilos of other insects in a season, more than 100,000 insects, mainly honey bees,” says Rob Voesten, who as an independent hornet expert monitors and combats the advance of the insect on behalf of various provinces. “If they have made a nest in your hedge and you suddenly come up with pruning shears, they can be extremely aggressive.”

At first, according to Voesten’s figures, the number of hornet nests grew quite slowly: from 1 in 2017 to 23 in 2021. Since then, the number of Asian hornets has increased exponentially. “Last year there were already 146 nests and this year so far 305.” The fence is off the dam, according to Voesten. For the time being, the Asian hornet is opted to exterminate as much as possible, for example by placing nests and queens in the freezer. This is also the strategy for ant species, crayfish and spiders.

To control, to control, to eradicate – the question is how long that is tenable. “We should think more about how we can make ecosystems more resilient to newcomers in the long term,” says Drukker. A more diverse nature is often more resistant to change. But even healthy ecosystems cannot cope with invasions such as those of the Asian hornet and the American crayfish. In any case, the Netherlands will have to learn to live with all kinds of new creatures in the coming years. One more innocent than the other.