Preface Economic, social and cultural activities, as well as environmental and human impacts, are increasingly concentrated in and around cities. In the era of planetary urbanization and technological revolution, cities have transformed beyond their proper borders into hinterlands, city-regions, urban corridors, and megaregions. As a consequence, development challenges have become far more complex than were anticipated in the 'traditional' conception of the 'city'. Transforming beyond their

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... ral and human resources and institutional capacity, cities currently face significant sustainability challenges in terms of governance; land and housing; basic services; food, water and energy security; and disaster risks.