In this symposium convened to celebrate the tenth anniversary of David Harvey's "Justice, Nature and the Geography of Difference", it is fitting to re-visit key themes in that seminal work, including: (1) the mutual reciprocity between social and environmental changes; and (2) the contradictions that emerge from a dialectical analysis of these changes in urban spaces. In challenging scholars to explore the spatial dialectics associated with environmental and social changes, Harvey's political and intellectual project included demonstrating the dialectical linkages between notions of justice and nature in urban environments. My work responds to Harvey's challenge by documenting how the ideological constructions of "home", "homeless" and "public green space" produce and perpetuate injustices experienced materially and spatially in the daily lives of homeless people living in urban green spaces. Using Agamben's notion of bare life as my analytic framework, I explore two issues: (1) the disconnection between notions of home articulated by homeless people living in green spaces and the ideological constructions of homeless espoused by government and planning agencies; and (2) the tensions in urban green spaces resulting from homeless people who have opted to live there because all other options are not viable for them, and the ideological constructions of urban green spaces developed by the city parks department and housed citizens involved in planning for future green spaces in the city. I present the concept of "ecological gentrification", which I define as the implementation of an environmental planning agenda related to public green spaces that leads to the displacement or exclusion of the most economically vulnerable human population - homeless people - while espousing an environmental ethic. I conclude by advocating a robust pluralism of "home" and "public green spaces" as an initial movement towards renegotiating concepts of justice in urban areas. I present short- and long-term strategies for resisting the displacement, exclusion and expulsion of homeless individuals from public urban green spaces with the goal of improving their material and spatial lives, and argue that such strategies require a re-imagined practice of urban ecological planning that draws inspiration from Harvey's commitment to producing spaces of justice, nature and difference. Copyright (c) 2009 The Author. Journal Compilation (c) 2009 Joint Editors and Blackwell Publishing Ltd.

N atural and social scientists addressing complex ecological problems increasingly recognize the value of one another's research, and often seek multidisciplinary, interdisciplinary, or transdisciplinary approaches to investigate real-world issues. A multidisciplinary approach involves researchers from two or more disciplines working collaboratively on a common problem, without modifying disciplinary approaches or developing synthetic conceptual frameworks. An interdisciplinary approach involves the use of an innovative conceptual framework to synthesize and modify two or more disciplinary approaches to deal with a research problem. Finally, a transdisciplinary approach involves nonacademic practitioners working with academics to identify, research, and develop solutions to real-world problems (Tress et al. 2003).Interdisciplinarity, in particular, is heralded as an educational paradigm that can meet the ecological challenges of the coming century (Palmer et al. 2005). The challenge is to develop collaborative partnerships among researchers to explore the complexity of human-nature interactions (Grimm et al. 2000). Interdisciplinary education exposes students to research in multiple disciplines, trains them in collaborative methods through team research, and promotes new forms of communication and collaboration among disciplines. The goal of interdisciplinary education is to develop new researchers and educators in "science at the leading edge" to effectively address pressing societal and environmental problems (Leshner 2004). Interdisciplinary, and now transdisciplinary, research and training are often part of university mission statements and course curricula, and are explicitly Jessica K. Graybill (e-mail: jgraybill@mail.colgate

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Dubai has been in the midst of a profound physical transformation, radically affecting the lives of residents and newcomers. Within US and European models of planning, the rapid change Dubai is experiencing calls for public involvement in charting the city's future. However, Dubai's neo-patrimonial governance concentrates planning decisions into the hands of trusted elites, lacking public participation. How might a participatory approach to planning be successfully implemented in Dubai? First, this article applies Delphi to obtain experts' knowledge about the feasibility of implementing a participatory planning approach in Dubai. Second, the first author interviewed government officials to identify constraints for implementing strategies intended to widen public participation. Last, recommendations for the implementation of a more transparent approach to planning are provided. The article concludes with questions that explore the challenges associated with participation in planning decision-making specifically for neo-patrimonial systems.

This research responds to calls from within the field of urban ecology to explicitly incorporate humanities-based research in order to achieve robust interdisciplinarity. Our research provides an example of a place-based urban ecological analysis. We use this framework to analyze over a century of park planning and development within the city of Seattle. We identify four eras of park planning that are linked by a comprehensive 100-year park plan. This case study examines how the political, cultural, and economic aspects of park planning have produced and been influenced by long-term trends and historical contingencies. This research also offers practical insights for effective contemporary urban planning, emphasizing the need for flexible and adaptive long-term plans when confronted with unpredictable events, emerging political arrangements, changing cultural priorities, and shifting fiscal climates.