Integration of urban science and urban climate adaptation research: opportunities to advance climate action

There is a growing recognition that responding to climate change necessitates urban adaptation. We sketch a transdisciplinary research effort, arguing that actionable research on urban adaptation needs to recognize the nature of cities as social networks embedded in physical space. Given the pace, scale and socioeconomic outcomes of urbanization in the Global South, the specificities and history of its cities must be central to the study of how well-known agglomeration effects can facilitate adaptation. The proposed effort calls for the co-creation of knowledge involving scientists and stakeholders, especially those historically excluded from the design and implementation of urban development policies.

A transition management framework to stimulate a circular phosphorus system

As the global population is projected to increase by two billion people by 2050, so will the demand for phosphorus (P), an essential nutrient for all living organisms and a major driver of eutrophication. To sustainably meet these challenges, we apply the conceptual framework of transition management (TM) to demonstrate how the trajectory of the current linear P use system could be strategically shifted toward a more circular P system. We present US case studies to examine P transitions management in intensive agriculture, wastewater disposal, and food waste management. Our goal is twofold. By first understanding past transitions in P management in the USA, we can build upon these insights for future management. This can then be applied to other global regions such as developing countries to bypass stages of transition as they intensify agriculture, incorporate sewers into cities, and expand waste management, to avoid becoming entrenched in unsustainable P management. We suggest how spaces for experimentation and collaboration can be created, how and which actor networks can be mobilized, and what action strategies and policies can be recommended to accelerate their transition to P sustainability. Our case studies show that while substantial improvements have been made, the transition toward a circular economy of P is far from complete. Our findings point to the value of utilizing TM for future progress in the US Development of TM frameworks for managing P in other regions of the world may enable them to achieve sustainable P development faster and more effectively than the USA.

How Does a Divided Population Respond to Change?

Most studies on the response of socioeconomic systems to a sudden shift focus on long-term equilibria or end points. Such narrow focus forgoes many valuable insights. Here we examine the transient dynamics of regime shift on a divided population, exemplified by societies divided ideologically, politically, economically, or technologically. Replicator dynamics is used to investigate the complex transient dynamics of the population response. Though simple, our modeling approach exhibits a surprisingly rich and diverse array of dynamics. Our results highlight the critical roles played by diversity in strategies and the magnitude of the shift. Importantly, it allows for a variety of strategies to arise organically as an integral part of the transient dynamics—as opposed to an independent process—of population response to a regime shift, providing a link between the population's past and future diversity patterns. Several combinations of different populations' strategy distributions and shifts were systematically investigated. Such rich dynamics highlight the challenges of anticipating the response of a divided population to a change. The findings in this paper can potentially improve our understanding of a wide range of socio-ecological and technological transitions.

Critical transition between cohesive and population-dividing responses to change

Globalization and global climate change will probably be accompanied by rapid social and biophysical changes that may be caused by external forcing or internal nonlinear dynamics. These changes often subject residing populations (human or otherwise) to harsh environments and force them to respond. Research efforts have mostly focused on the underlying mechanisms that drive these changes and the characteristics of new equilibria towards which populations would adapt. However, the transient dynamics of how populations respond under these new regimes is equally, if not more, important, and systematic analysis of such dynamics has received less attention. Here, we investigate this problem under the framework of replicator dynamics with fixed reward kernels. We show that at least two types of population responses are possible—cohesive and population-dividing transitions—and demonstrate that the critical transition between the two, as well as other important properties, can be expressed in simple relationships between the shape of reward structure, shift magnitude and initial strategy diversity. Importantly, these relationships are derived from a simple, yet powerful and versatile, method. As many important phenomena, from political polarization to the evolution of distinct ecological traits, may be cast in terms of division of populations, we expect our findings and method to be useful and applicable for understanding population responses to change in a wide range of contexts.