The establishment of interdisciplinary Master’s and PhD programs in sustainability science is opening up an exciting arena filled with opportunities for early-career scholars to address pressing sustainability challenges. However, embarking upon an interdisciplinary endeavor as an early-career scholar poses a unique set of challenges: to develop an individual scientific identity and a strong and specific methodological skill-set, while at the same time gaining the ability to understand and communicate between different epistemologies. Here, we explore the challenges and opportunities that emerge from a new kind of interdisciplinary journey, which we describe as ‘undisciplinary.’ Undisciplinary describes (1) the space or condition of early-career researchers with early interdisciplinary backgrounds, (2) the process of the journey, and (3) the orientation which aids scholars to address the complex nature of today’s sustainability challenges. The undisciplinary journey is an iterative and reflexive process of balancing methodological groundedness and epistemological agility to engage in rigorous sustainability science. The paper draws upon insights from a collective journey of broad discussion, reflection, and learning, including a survey on educational backgrounds of different generations of sustainability scholars, participatory forum theater, and a panel discussion at the Resilience 2014 conference (Montpellier, France). Based on the results from this diversity of methods, we suggest that there is now a new and distinct generation of sustainability scholars that start their careers with interdisciplinary training, as opposed to only engaging in interdisciplinary research once strong disciplinary foundations have been built. We further identify methodological groundedness and epistemological agility as guiding competencies to become capable sustainability scientists and discuss the implications of an undisciplinary journey in the current institutional context of universities and research centers. In this paper, we propose a simple framework to help early-career sustainability scholars and well-established scientists successfully navigate what can sometimes be an uncomfortable space in education and research, with the ultimate aim of producing and engaging in rigorous and impactful sustainability science.Electronic supplementary materialThe online version of this article (doi:10.1007/s11625-017-0445-1) contains supplementary material, which is available to authorized users.

The stability and resilience of the Earth system and human well-being are inseparably linked1–3, yet their interdependencies are generally under-recognized; consequently, they are often treated independently4,5. Here, we use modelling and literature assessment to quantify safe and just Earth system boundaries (ESBs) for climate, the biosphere, water and nutrient cycles, and aerosols at global and subglobal scales. We propose ESBs for maintaining the resilience and stability of the Earth system (safe ESBs) and minimizing exposure to significant harm to humans from Earth system change (a necessary but not sufficient condition for justice)4. The stricter of the safe or just boundaries sets the integrated safe and just ESB. Our findings show that justice considerations constrain the integrated ESBs more than safety considerations for climate and atmospheric aerosol loading. Seven of eight globally quantified safe and just ESBs and at least two regional safe and just ESBs in over half of global land area are already exceeded. We propose that our assessment provides a quantitative foundation for safeguarding the global commons for all people now and into the future.

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