The decline in biodiversity and the associated loss of plant species are greatly affecting our ecosystems. Thus far, this has been shown by studies in the so-called grassland, i.e. in areas that are not covered by buildings or are dominated by woody vegetation. A team of biologists has now been able to show that the loss of tree species in forests destabilizes insect communities and their interactions with each other and with plants. Tree diversity in forests is therefore important for stabilizing the insects’ food webs.