Pesticides safeguard agricultural yields by controlling insects, fungi, and weeds. However, they also enter streams and damage the aquatic communities. In a nationwide monitoring program, scientists led by the Helmholtz Centre for Environmental Research have shown that the governmental thresholds for pesticides are too high and that these levels are still exceeded in over 80% of water bodies. The loss of biodiversity can only be halted if the environmental risk assessment of pesticides is revised.