Urban resilience has conventionally been defined as the "measurable ability of any urban system, with its inhabitants, to maintain continuity through all shocks and stresses, while positively adapting and transforming towards sustainability".
Therefore, a resilient city is one that assesses, plans and acts to prepare for and respond to hazards, regardless whether they are natural or human-made, sudden or slow-onset, expected or unexpected. Resilient Cities are better positioned to protect and enhance people's lives, secure development gains, and drive positive change.
History
According to the urban historian Roger W. Lotchin the 2nd World War had an profound environmental impact on urban areas in the USA. By 1945 Pittsburgh and other cities along the Mississippi River experienced air pollution comparable to the Dust Bowl. The environmental impact of the 2nd World War turned urban areas around the world into shock cities. Extreme cases of hard hit cities include Hiroshima, Chongqing, Stalingrad, and Dresden. Environmental history first emerged as an academic research topic in the 1970s, focusing initially on rural areas. Pioneers of urban environmental history include Martin Melosi, Christine Rosen, Joel A. Tarr, Peter Brimblecombe, Bill Luckin, and Christopher Hamlin. Recurrent climate changes have prompted renewed interest in this academic field. The concern for urban resilience in the urban planning of cities has become increasingly visible in recent years, partly because urban resilience can be used to describe the change in structure and function of urban areas. Social scientists have taken an increased interest in ecological resilience, because the links between social-ecological systems are being examined. Urban resilience is no longer the preserve of academics, urban policy documents around the globe are putting forward proposals to enhance the urban resilience of cities. The definition of urban resilience may vary, but are no longer limited to the speed at which an urban systems recover after a shock.
Academic research focus
Academic discussion of urban resilience has focused primarily on three threats; climate change, natural disasters, and terrorism.
Accordingly, resilience strategies have tended to be conceived of in terms of counter-terrorism, other disasters (earthquakes, wildfires, tsunamis, coastal flooding, solar flares, etc.), and infrastructure adoption of sustainable energy. More recently, there has been an increasing attention to the evolution of urban resilience and the capability of urban systems to adapt to changing conditions. This branch of resilience theory builds on a notion of cities as highly complex adaptive systems. The implication of this insight is to move urban planning away from conventional approaches based in geometric plans to an approach informed by network science that involves less interference in the functioning of cities. Network science provides a way of linking city size to the forms of networks that are likely to enable cities to function in different ways. It can further provide insights into the potential effectiveness of various urban policies. This requires a better understanding of the types of practices and tools that contribute to building urban resilience. Genealogical approaches explore the evolution of these practices over time, including the values and power relations underpinning them.
Investment decisions
Building resilience in cities relies on investment decisions that prioritize spending on activities that offer alternatives, which perform well in different scenarios. Such decisions need to take into account future risks and uncertainties. Because risk can never be fully eliminated, emergency and disaster planning is crucial. Frameworks for disaster risk management, for example, offer practical opportunities for enhancing resilience.
More than half of the world's human population has lived in cities since 2007, and urbanization is calculated to rise to 80% by 2050. the growing urbanization over the past century has been associated with a considerable increase in urban sprawl. Resilience efforts address how individuals, communities and business not only cope on the face of multiple shocks and stresses, but also exploit opportunities for transformational development.