John Zacharias
Article: The Dynamics of People Movement Systems in Central Areas
Challenges 2011, 2(4), 94-108; doi:10.3390/challe2040094 - published online 29 November 2011
Show/Hide AbstractAbstract: Certain pedestrian facilities, by their nature and the spatial imperatives they impose, exert a powerful role in organizing and promoting the development of associated central places. The need for an expanded public space in the city has found expression in the new public spaces that have emerged in relation to this transport infrastructure within long developed urban environments. In contemporary, advanced urban society, such new spaces need to have polyvalent purposes and to respond to emergent demands. It is proposed that certain characteristics of these pedestrian systems support intensification and multiplication of activities over a particular spatial environment defined by activities. In the three cases—the Underground system of Montreal, Tokyo Station City and the Central Mid-levels Escalator area—common characteristics proposed as important to the achievement of the developmental goals include specific spatial relations, system open-endedness and structural complexity.

Atiq Uz Zaman and Steffen Lehmann
Article: Challenges and Opportunities in Transforming a City into a “Zero Waste City”
Challenges 2011, 2(4), 73-93; doi:10.3390/challe2040073 - published online 2 November 2011
Show/Hide AbstractAbstract: The currently consumption-driven society produces an enormous volume of waste every day. Continuous depletion of natural finite resources by urban populations is leading the globe to an uncertain future. Therefore, to prevent further depletion of global resources, sustainable consumption and a strategic waste management system would be required. It is evident that a significant number of global non-renewable resources such as cadmium, mercury and tellurium will experience permanent shortfall in global supply within the next two to three decades. Astonishingly, the current recycling rate of these very scarce metals is significantly low in all cities around the globe. The concept of the zero waste city includes a 100% recycling of municipal solid waste and a 100% recovery of all resources from waste materials. However, transforming currently over-consuming cities into zero waste cities is challenging. Therefore, this study aims to understand the key factors waste management systems in cities such as consumption, resource depletion and possible decoupling opportunity through implementing the “zero waste city” concept. The study proposes five significant principles for transforming current cities into zero waste cities in the context of long-term sustainability. A simultaneous and harmonized application of sustainable behaviour and consumption, product stewardship, a 100% recycling and recovery of resources, legislated zero landfill and incineration are required to transform current city into a zero waste city.

Brian McGrath and S. T. A. Pickett
Article: The Metacity: A Conceptual Framework for Integrating Ecology and Urban Design
Challenges 2011, 2(4), 55-72; doi:10.3390/challe2040055 - published online 20 October 2011
Show/Hide AbstractAbstract: We introduce the term metacity as a conceptual framework that can be shared by ecologists and designers and applied across the wide variety of urban habitats found around the world. While the term metacity was introduced by UN-HABITAT to designate hyper cities of over twenty million people, for us it is not limited to large urban agglomerations, but rather refers to the proliferation of new forms of urbanization, each with distinct ecological and social attributes. These various urban configurations when combined with new digital sensing, communication and social networking technologies constitute a virtual meta-infrastructure, present in all cities today. This new metacity has the potential to integrate new activist forms of ecological and urban design research and practice in making the transition from sanitary to sustainable city models globally. The city of Baltimore, Maryland will be used both as a site to illustrate these recent urban trends, and also as an example of the integration of ecology and urban design pursued by the two authors over the past seven years [1,2]. Metacity theory is drawn from both an architectural analysis of contemporary forms of urbanism, new forms of digital monitoring and communication technologies, as well as metapopulation and metacommunity theories in ecology. We seek to provide tools and lessons from our experiences for realizing an integrated metacity approach to achieving social sustainability and ecological resilience on an increasingly urbanized planet.

Jon Burley , Gina Deyoung , Shawn Partin and Jason Rokos
Article: Reinventing Detroit: Reclaiming Grayfields—New Metrics in Evaluating Urban Environments
Challenges 2011, 2(4), 45-54; doi:10.3390/challe2040045 - published online 27 September 2011
Show/Hide AbstractAbstract: Planners, designers, citizens, and governmental agencies are interested in creating environments that are sustainable and fulfill a wide range of economic, ecological, aesthetic, functional, and cultural expectations for stakeholders. There are numerous approaches and proposals to create such environments. One vision is the 1934 “Broadacre City” proposed by Frank Lloyd Wright for the Taliesin, Wisconsin area that was never implemented. Frank Lloyd Wright’s vision integrated transportation, housing, commercial, agricultural, and natural areas in a highly diverse pattern forming a vast urban savanna complex. He also applied his “Broadacre City” idea to the 1942 Cooperative Homesteads Community Project in Detroit, Michigan, another un-built project. This vision concerning the composition of the urban environment may be conceptually realized in the ongoing gray-field reclamation in suburban Detroit, Michigan. Recent science-based investigations, concerning the metrics to measure and evaluate the quality of designed spaces, suggest that this “Broadacre City” approach may have great merit and is highly preferred over past spatial treatments (p ≤ 0.05). These metrics explain 67 to 80% of the variance concerning stakeholder expectations and are highly definitive (p < 0.001).

Douglas Paton
Announcement: Special Issue: Risk Management Challenges: Mitigate the Risk from Natural Hazards
Challenges 2011, 2(3), 44; doi:10.3390/challe2030044 - published online 4 July 2011
Show/Hide AbstractAbstract: Within minutes of the March 2011 earthquake in Japan, news media provided unprecedented coverage of an unfolding natural catastrophe. Events such as this place natural disasters firmly in the public eye but only for a short time. It falls to the research community to learn the lessons offered by these events and turn them into opportunities for developing more effective risk management and mitigation strategies and identifying the factors that contribute to the vulnerability and resilience of communities and response and recovery agencies. Disasters such as the Japanese tsunami also highlight the ever-present need for systematic, rigorous research into the risk posed by natural hazards and how these risks can be managed. Of course it is vital to ensure that the findings from such research endeavours are disseminated to those who can use the findings.

Kongjian Yu
Announcement: Special Issue: Challenges in City Design: Realize the Value of Cities
Challenges 2011, 2(2), 43; doi:10.3390/challe2020043 - published online 24 June 2011
Show/Hide AbstractAbstract: In 1900, only about 13% of the world’s population lived in cities; now the figure has increased to over 50%, and is expected to reach 60% by populations in cities and suburban areas, developing countries are still in the process of urbanization. Every day, hundreds and thousands of people move to the city. Why do we choose to concentrate ourselves in cities? What is the value of cities? What do cities offer us? [...]