Grand Challenges in Urban Science

Cities face a grand challenge: they must rethink themselves in the context of planetary change. Global urban development is a prominent feature of our new geological epoch, the Anthropocene (Crutzen and Stoermer, 2000; Though scientists disagree on exactly when the Anthropocene began Over the past century, the "great acceleration" of human activities associated with rapid urbanization has initiated fundamental ecosystem shifts that far exceed the natural range of variability exhibited during the Earth's previous half-million years These shifts represent uncharted territories for urban scholars, and the assumptions made by previous dominant theories and models (i.e., that the urban systems will respond predictably to urban pressures and to the feedbacks from environmental changes) are built upon structures of evidence of a world that no longer exists. The emergence of complex interactions among human, natural, and technological systems and the uncertain trajectories that characterize urban futures require that urban scientists critically review their assumptions and expand their capacity to ask new questions