<p>An understanding of ecosystems is important to enable biology teachers to teach ecological topics in their lessons. This exploratory study examines the systems thinking of pre-service biology teachers in the context of the forest ecosystem. In addition, the extent of their environmental awareness was determined (cognitive, conative, and affective components), as well as the correlations between these two constructs calculated. The 51 participants were recruited in biology education seminars (convenience sampling). They each created a concept map about the influence of climate change on the forest ecosystem and filled out a questionnaire about environmental awareness. Concept maps were analyzed to determine complexity based on the Components-Mechanisms-Phenomena framework and structural attributes (e.g., number of concepts), resulting in eleven systems thinking indicators in total. Results show that some indicators pointed to a rather high and others to a rather low level of systems thinking. On average, the participants were environmentally aware, whereby their conative environmental awareness was lower than their affective and cognitive awareness. Correlation analyses showed statistically significant positive correlations between the structural attributes and the participants’ environmental awareness. The correlations between the complexity attributes and the participants’ environmental awareness were statistically significantly positive in some cases. Hence, it becomes clear that systems thinking is not only associated with cognitive aspects, but also with conative and affective aspects of environmental awareness. Future research should aim to provide reasons for these relationships (e.g., using case studies or experimental designs) and examine whether our findings also apply to other contexts.</p>