In Amsterdam-Noord there is a small wilderness where the leaves are scarred by gluttony and yellow branches and grass shoot out in all directions. Here, far from neatly mowed lawns and neatly arranged hydrangeas, Butterfly Garden 'Mot in Mokum' is far from the chaos it seems: every plant has been carefully chosen to welcome butterflies.
Owner Nicky Castricum gestures to the lush garden, which has an area of just over three tennis courts. “This is what the countryside used to look like, before it turned into the fields of tight grass we see today – a dry desert for butterflies and insects. Nowadays the city offers more biodiversity than the countryside.”
CBS came this week with disturbing figures: the Dutch butterfly population has declined by as much as 53 percent since the first measurements in 1992 – in which butterflies are counted weekly on a fixed route. Last year was also a dramatic year, with the lowest numbers ever counted. Among the biggest declines were rare butterfly species such as the small heath butterfly and the gentian blue, but also better-known butterflies such as the small fox and the large cabbage white declined sharply.
The first sharp decline started in the 1990s. From 2002 to 2018, the populations remained fairly stable, but from that year onwards there was another sharp decline in the number of butterflies.
Kars Veling, biologist at the Butterfly Foundation, sees two clear causes for the declines: the first wave was due to intensive agriculture, which caused natural habitats to disappear. “Grasslands that are mowed six times a year no longer provide a home for our butterflies.”
The second sharp decline from 2018 is due to climate change. “The remaining butterflies are now further cornered. Butterflies thrive in warmth and reproduce well, but extreme drought causes dry leaves that are no longer nutritious for the caterpillars. We suspect that the strong decline in 2023 is the result of the successive dry summers in previous years.”
Nature-inclusive agriculture is vital for the recovery of butterfly populations, says Veling: “Farmers must give more space to nature on agricultural land. If this happens on a large scale, we can reduce nitrogen and butterflies can reproduce in agricultural areas again.” Fortunately, municipalities are increasingly active in the ecological management of road verges, he says; natural roadsides are “excellent habitats for butterflies and insects.”
Private individuals can also do a lot: with a butterfly-friendly garden, for example. And it's not that complicated, says Veling: “A garden full of plants is a good start, choosing native species is a lot better and unsprayed native plants are best.” Native plants have adapted to Dutch butterflies over the centuries, providing an ideal food supply and habitat.
Nicky Castricum from the Amsterdam Butterfly Garden agrees. “Nature is very different from gardening,” he says. For example, insects “have little use in a neat, colorful border, where their eggs do not survive due to frequent pruning.” Castricum advises municipalities on butterfly-friendly measures and provides courses to schools, biologists and gardeners. “We will soon all go to the garden center again, full of good intentions to give nature a helping hand.”
And there are still some profits to be made at those garden centers, says Castricum: too often, according to him, we choose “the beautiful flowers, which serve our eyes more than the insects. If you really want to help butterflies, choose native, poison-free plants.” Garden centers often stick out for marketing reasons random a butterfly picture with beautiful flowers, says Castricum: “People see large flowers with a butterfly picture and think they are there.” But these plants are often only useful during the butterfly phase – butterflies only flutter around for a few weeks – and not during the rest of the life cycle.
Photos: Ramon from Flymen
Take the popular butterfly bushes, which live up to their name and sometimes attract a lot of butterflies with their plume-shaped flowers in the summer – very nice, but that's not enough. Castricum: “They offer no place for eggs or hibernation. I often hear it: people put up a plant, see insects and think they are doing well.” But the life of butterflies largely takes place out of our sight, he explains. That is why he advocates native plants in the garden: “This supports every phase of the butterfly's life: from caterpillar and pupa to the hibernation of a butterfly.”
There is something else going on when it comes to those brightly colored bloomers in garden centers: if they have been treated with poison, they pose a serious threat to insects. “Many garden centers sell plants that have been treated with pesticides. After all, we prefer to buy plants without holes or discolorations.” Our view of gardening must therefore change, he says. “Leaves full of holes or that have died have served their purpose: feeding insects. A perfect looking ivy has probably been sprayed with pesticides. Beautiful for us, but harmful to butterflies.”
Both butterfly experts emphasize that the focus of monitoring is on butterflies – because of the widely held affinity with these insects. But, they say, it is likely that the large decline also occurs in other insects. The situation could therefore be a lot more worrying than is currently known: “If there are too many holes in the bottom layer of the food chain, the whole house of cards will eventually collapse.”
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