Organisms interact with each other in nature. For example, predator-prey relationships lead to food webs, which in turn can affect ecosystem functions such as primary production or the decomposition of fallen leaves. In order to understand how human actions influence these complex interactions, studies in the laboratory, in model ecosystems (mesocosms) and also in the field involving invertebrates are necessary. The knowledge thus gained allows us to develop and refine predictions about future developments in response to further stressors, such as the release of pollutants. These efforts as a whole form an important basis for political and social decisions to protect nature and thus preserve the basis of our existence.