Complex anthropogenic challenges such as climate change, biodiversity loss, land use change, resource overuse, or novel entities in the environment are already affecting ecosystems and societies around the world ^[1][2][1,2]. The responsible handling of these major environmental and socio-economic challenges needs more than “business-as-usual-solutions” [3]. Instead, a profound social, economic, and political shift toward more sustainable lifestyles is needed to achieve global climate goals such as climate neutrality ^[2][4][5][2,4,5]. Decision makers in politics, the economy, and civil society play an important role in the collective journey towards sustainability, as they make far-reaching and high-impact decisions leading to major changes [6]. Therefore, decision makers with high-level responsibilities in economics, politics, and civil society require more sustainability competencies than the average citizen. These include perceiving and understanding the world as an interplay of complex systems, committing to values, and far-sighted strategizing as well as communicating in an engaging way [3]. Educational programs regarding sustainability therefore need to incorporate these competencies in order to enable future decision makers to steer societal transformation towards a sustainable future.

2. How to Deal with Challenges in Sustainability–Private-Sphere and Public-Sphere Actions

Urgent challenges in sustainability require a deep societal transformation, not only individual changes in consumer behavior. In all industrialized countries, climate policy is confronted with the increasing demand for a post-fossil, carbon-neutral world [2]. In the debate on how to deal with these challenges and to shape sustainable development, profound changes in both private-sphere actions and public-sphere actions are needed [6]. A sustainable transformation cannot be achieved through changes in the private sphere alone. While individual consumer behavior or lifestyle choices (e.g., choosing a bicycle over a car or saving energy at home) are one component of steering civil society towards a sustainable future, macroscale decisions in the public sphere, such as industrial production patterns and political frameworks ^[7][8], are more significant. Niebert ^[8][9] points out that primarily political, economic, and structural decisions are most effective environmentally. He illustrates this with historical examples of successful solutions for complex environmental problems, such as stopping ozone depletion, phasing out nuclear power, and improving air quality in Europe, which were all solved through political regulation. The results published by Steinebach ^[9][10] provide additional evidence that the most effective actions are taken by leaders in politics, the economy, and civil society. Limiting emissions, reducing pollution, and restricting unsustainable consumption of natural resources at a public-sphere level have been shown to be more effective when leaders decide on conservative measurements, which are then compulsory for larger social groups [6]. Further evidence of this is provided by an analysis of emissions during the COVID-19 pandemic-related lockdowns. It became particularly evident that it is not the average consumer making a difference, but rather multinational corporations should be held accountable for their vast environmental impact ^[10][11]. Emissions were reduced by only 17% despite strong restrictions in the private sphere, such as the significant decrease in private and business travel and overall decreasing mobility due to compulsory home offices ^[10][11]. The fact that 70% of the emissions come from fossil fuel producers makes sustainable transformation predominantly a political task ^[10][11] (p. 11). The 21st century society now demands different skills and values from decision makers in the private, corporate, and non-profit sector than during the past decades ^[11][12]. Socially and especially environmentally responsible criteria for decision making continue to grow in importance in public reasoning. In order to steer societal transformation towards a sustainable future, sustainable development initiatives and projects have emerged and aim to provide leadership teams with knowledge on urgent sustainability challenges and the necessary competencies to manage societal change ^[7][8] (p. 24). Education plays a crucial role when it comes to sustainable development. “A large-scale educational transformation is needed to equip a new generation of professionals” [3] (p. 241) towards a more sustainable future. Many approaches in ESD tend to address private-sphere actions by convincing the broader public to change their consumer habits ^[12][13]. Choosing a bike, bus, and train over car and aircraft; a plant-based diet over meat; and replacing fossil-based sources of heating with sustainable ones in private housing are among the most popular examples ^[12][13]. This way, learners are taught that their everyday decisions contribute to a better future. The overall responsibility to solve complex problems—such as the global climate crisis, loss of biodiversity, and pollution—is focused on individuals instead of on the big players ^[13][14]. However, the focus on private-sphere actions is not sufficient in terms of substantially reducing greenhouse gasses ^[14][15]. Public-sphere actions and adjustments, such as legal measures or subsidies designed as incentives to reduce CO₂ emissions at a national level, are needed as effective political strategies to reduce greenhouse emissions ^[14][15]. One way to bridge the distance between the private sphere—the domain of individuals—and the public sphere—the domain of decision makers and public actions—is to develop educational programs that enable individuals to actively seek opportunities to participate in decision making at the local and societal level in a meaningful way. Within the academic fields of ESD, several competency models have been developed. Regardless of their target group (pupils, students, professionals), ESD suggests applying a specific set of key sustainability competencies, which will be discussed in the next subchapter. ThWe researchers will refer to selected approaches relevant to the underlying research question and study design.

3. Competencies and Key Competencies in Sustainability

Sustainability professionals require specific competencies in order to manage complex societal, economic, and political issues within a rapidly changing natural and technical world ^[11][12]. In recent decades, various models for sustainability-related competencies for understanding fundamental sustainable challenges and for developing a sustainable future have been suggested to help decision makers tackle these challenges in a participatory, cooperative, and solution-oriented way ^{[15][16][17][18][19][20]}[7,16,17,18,19,20]. This section presents terms and definitions relevant to the underlying research question and empirical endeavor of theour research. First, let us give a general definition of competencies. Competencies are “the cognitive abilities and skills available in or learned by individuals to solve specific problems, as well as the associated motivational, volitional, and social dispositions and skills to use the problem solutions successfully and responsibly in variable situations” [21] (p. 27). When it comes to sustainability challenges, there are specific sustainability competencies to deal with these challenges. Wiek et al. define sustainability competencies as “complexes of knowledge, skills, and attitudes that enable successful task performance and problem solving with respect to real-world sustainability problems, challenges, and opportunities” ^[15][7] (p. 204). Education for sustainable development—as an umbrella concept in education—should enable people to shape sustainable development and to critically reflect on individual contributions regarding a greater cause ^[18][22][18,22]. The overarching goal of most ESD approaches is the acquisition of specific sets of key competencies facilitating conscious, sustainable action in the field of education ^[18][20][23][18,20,23]. When thwe researchers are are talking about key competencies, the researchers we use the version defined by Brundiers et al. [24], who summarize a definition from different authors ^{[15][16][25][26][27][28]}[7,16,25,26,27,28]. They describe a key competence as “a distinctive and multifunctional competency, which is composed of several competencies that intersect with each other. […] It is essential for achieving successful performance and a positive outcome related to a particular endeavor in diverse contexts, for instance to achieve societal goals, which are normatively defined by their cultural context” [24] (p. 17). By applying the concept of key competencies to challenges in sustainability, you need key competencies in sustainability which, according to Wiek et al. ^[15][7] and Wals [29], consist “of several sustainability competencies that functionally relate to each other. It facilitates achieving successful performance and a positive outcome that progresses sustainability […], while working on specific sustainability challenges and opportunities in a range of contexts” [24] (p. 17). There are different international frameworks of key competencies in sustainability. In German-speaking countries, the concept of “Gestaltungs-kompetenz” developed by de Haan and Harenberg [30] is often applied. This refers to the ability to apply knowledge about sustainability and “to enact changes in economic, ecological and social behavior without such changes always being merely a reaction to pre-existing problems” [20] (p. 22). However, the “Gestaltungskompetenz” model has often been criticized for its lack of globalism and international perspective [18]. Around the same time, the international project Definition and Selection of Competencies: Theoretical and Conceptual Foundations (DeSeCo) of the Organization for Economic Co-operation and Development (OECD) formulated a framework of “key competencies for a successful life and a well-functioning society” [19]. Primarily, these were developed for OECD countries, but can also be useful for other countries [18]. More recently—in 2022—the Joint Research Center (JRC) published a Science for Policy Report for the European context and as an input to the EU policymaking process [31]. This European Sustainability Competence Framework (GreenComp) should support educators and learners to develop a common understanding of sustainability. It consists of four areas: (1) embodying sustainability values, (2) embracing complexity in sustainability, (3) envisioning sustainable futures, and (4) acting for sustainability. In these four areas, 12 sustainability competencies are organized [31]. The UNESCO publication “Education for Sustainable Development Goals (SDGs): Learning Objectives” [16] presented a set of competencies that attempts to meet the current challenges posed by the SDGs and bundle a very broad debate on ESD competencies. The competencies identified from different competency models by UNESCO are systems thinking, normative thinking, strategic thinking, critical thinking, self-awareness, and integrated problem-solving (p. 10). These competencies are also defined as “cross-cutting competencies” which are transversal and context-independent. They are not specific or “replace specific competencies necessary for successful action in certain situations and contexts” [16] (p. 10). Similar to UNESCO’s work, Wiek et al. ^[15][7] have formulated the five key competencies in sustainability, which thwe researchers will focus on in this publication. This is one of the most influential and most referenced studies (2397 Google Scholar citations, 5 January 2023) in the field and is often seen and applied as the fundamental work of key competencies in sustainability ^[24][32][24,32]. Moreover, the competence model has served as an analytical framework for empirical interview inquiries. It is a critical reference point in sustainability education for developing the sustainability competencies of students expected to be future sustainability leaders. Table 1 shows a brief explanation of the five key competencies to better understand which key terms we used in the in our analysis.