Global urbanization as a shifting context for applying ecological science toward the sustainable city

There is an abundance of conceptual frameworks relevant to sustainability in urban systems.However,to advance urban ecological science and its application to sustainable urban transformations,key existing frameworks must be synthesized.This paper is a conceptual synthesis cast in essay form in order to encompass a broad range of relevant ideas.It starts from the premise that the familiar models of metropolitan and megalopolitan urban structure,of industrially driven urban development,and of the contrasts between urban and non-urban lands are manifestly inadequate representations of evolving global reality.Such inadequacy is illustrated with examples from the United States and from China.Both the form and the interactions involved in contemporary urbanization and urban change suggest the need for a new integrated framework synthesizing two existing yet still evolving concepts:(1)The urban megaregion framework accommodates the spatial extent,interdigitation of contrasting land uses,and the linked spatial relations between nominally urban and nominally rural areas.(2)The new concept of the continuum of urbanity emphasizes the shifts in livelihood and lifestyle driven by regional and global teleconnections and their joint effects on local environments and landscapes.Together these frameworks suggest a common conceptual structure for addressing urban areas of different ages,sizes,forms,and dynamics in both urbanizing and urbanized areas in developing and developed countries and regions.The synthesis of frameworks points to empirical research needs,and has the potential to better match sustainability plans and actions with the diverse urban forms and dynamics now appearing around the world.

Wastewater reclamation and reuse in China:Opportunities and challenges

The growing water stress both in terms of water scarcity and quality deterioration promotes the development of reclaimed water as a new water resource use. This paper reviewed wastewater reuse practices in China, and the opportunities and challenges of expanding reclaimed water use were analyzed. Rapid urbanization with the increasing of water demand and wastewater discharge provides an opportunity for wastewater reuse. The vast amount of wastewater discharge and low reclaimed water production mean that wastewater reuse still has a great potential in China. Many environmental and economic benefits and successful reclamation technologies also provide opportunities for wastewater reuse. In addition, the overall strategy in China is also encouraging for wastewater reuse. In the beginning stage of wastewater reclamation and reuse, there are many significant challenges to expand wastewater reuse in China including slow pace in adopting urban wastewater reuse programs, the establishment of integrated water resources management framework and guidelines for wastewater reuse programs, incoherent water quality requirements, the limited commercial development of reclaimed water and the strengthening of public awareness and cooperation among stakeholders.