Abstract:For the past decade “megaregions”—very large-scale constellations of urban regions—have been a popular focus of attention at academic conferences. They have also attracted the attention of non-governmental organizations (NGOs) specializing in urban and regional planning as well as governmental agencies at multiple levels. It is easy to see why. Thinking at a (relatively) new scale generates intellectual excitement as well as new research and funding opportunities. Researchers have been able to create intriguing maps showing the new urban geographies. This larger scale of planning brings into play attractive technologies such as high-speed rail. Equally importantly, it provides a respite from the challenge of dealing with the gridlocked politics and often ineffective institutions at other levels. As a result of such factors, efforts at megaregional planning and infrastructure development are gaining speed, with few voices raised in opposition. However, rather than helping bring about more sustainable societies this new scale of planning is likely to accelerate what some climate change scientists have labeled BAU— “business-as-usual” forms of development. If conducted primarily to coordinate new infrastructure or to promote globalized forms of economic development, the consequences of megaregional planning are likely to be disastrous. The result may well be to facilitate the physical sprawl of urban development between cities, to increase the amount that people travel and associated greenhouse gas emissions, to worsen disparities between different populations and communities, and to strengthen economic globalization trends that undermine local place and global sustainability. In this chapter I will develop the case that megaregional planning and research should thus be undertaken with a very cautious eye, within the larger umbrella of a move towards more local and sustainable communities.