For example, mowing roadsides and green strips on dikes and along the railways will certainly lead to the death of many butterflies in June and July, De Vlinderstichting tells

Still, according to the foundation, mowing is also necessary in the butterfly peak season to guarantee the survival of butterfly species.

"I always say: mowing is killing. But it has to happen," explains ecologist Kars Veling of De Vlinderstichting.

"If you don't mow, the flowers are overgrown by other plants and the grassland becomes a forest. Then the butterflies no longer have a habitat and they disappear completely."

According to Veling, it is not a problem that many butterflies die as a result of mowing.

"If a bird loses half its young, that loss is great. But insects take into account enormous deaths within their population by laying enormous numbers of eggs. That has grown in evolution."

Veling warns that not all flowers in the habitat of butterflies should be mown away at once.

According to the ecologist, it is important to leave small pieces of grassland with flowers with every mowing.