On the ‘complexity turn’ in planning: An adaptive rationale to navigate spaces and times of uncertainty

Complexity sciences have been long ago acknowledged to be useful at conceptualizing a variety of phenomena relevant to planning. Nevertheless, the actual mechanisms that will prove adequate to tackle complex planning issues are still under debate. Considering that in today’s so-called era of the Anthropocene such planning issues are more present and evident than ever, the need for further investigating the implications of complexity sciences into building planning approaches becomes very relevant. In this article, we use the concept of complex systems as an analytical framework challenging our understanding of planning and we argue in favour of a ‘complexity turn’ in planning through the adaptive rationale. We define the adaptive rationale as an additional, both normative and analytical, trajectory in planning theory, in the interplay between certainty and uncertainty. Finally, to assimilate this rationale into planning mechanisms capable to respond to contemporary social and ecological challenges, we call for issue-driven adaptive planning approaches conceptualized through normative sustainability and nourished by post-normal science.