The debate on the possible impact of genetically modified (GM) crops on biodiversity shows that so far there is no consensus on generally accepted assessment criteria for environmental harm. This debate stems primarily not from a shortage of data, but rather from the absence of criteria for assessing the effects of GM plants on biodiversity. Since there are no exact assessment criteria, regulatory decision-making processes are often not transparent and can be difficult to understand. This increases the danger that decisions on environmental risks from GM plants may appear arbitrary. The aim of the VERDI Project (Valuating environmental effects of genetically modified crops - ecological and ethical criteria for regulatory decision-making) is to develop recommendations for decision makers and licensing authorities, thus helping to improve the regulation of GM plants. The results show that both the unambiguous description of protection goals and the establishment of a basis of comparison are two essential criteria when defining harm. In the project we are working on suggestions for improving these two criteria.