3.3.1. Interdisciplinarity and Transdisciplinarity

Successful development of sustainable solutions in urban areas requires integrating knowledge and skills from multiple perspectives, and so a common theme for all competencies is the ability to think across disciplinary and institutional boundaries. The concepts of interdisciplinarity and transdisciplinarity are often referred to in ESD literature. Interdisciplinary education aims to teach students subjects from multiple perspectives, developing students' abilities to synthesize knowledge from different disciplines, change perspectives, and cope with complexity [28]. Transdisciplinary education extends this further, entailing solution-oriented collaboration between academics and non-academic actors [20,27,29] and bringing the world outside of the HEI into student education [20]. Lang et al. [27] define transdisciplinarity in broad terms as follows:

"Transdisciplinarity is a reflexive, integrative, method-driven scientific principle aiming at the solution or transition of societal problems and concurrently of related scientific problems by differentiating and integrating knowledge from various scientific and societal bodies of knowledge."

As there is no single discipline that would cover the various aspects of SUD, interdisciplinary and transdisciplinary approaches—rather than monodisciplinary—are important (see, e.g., [30–32]). As a result, inter-/transdisciplinary education and research have started to become more commonplace although the monodisciplinary tradition still dominates HEI teaching practices. Indeed, a number of studies have discussed the importance of HEI teaching of sustainability aiming for transdisciplinary problem-based learning instead of the accumulation of discipline-based knowledge [33], and evidence suggests that it can improve course outcomes [34].
