MESSAGE FROM THE PRESIDENT GEORGE W. McCARTHY a framework for generating hypotheses and the Before we attempt to implement the New empirical analysis to test those theories. And the Urban Agenda, we must confront the serious Toward a Theory of Urban Evolution research, in general, focuses on big iconic cities, limitations in our understanding of cities and rather than a representative global selection of urban settlements that captures the differences urban evolution. A new “science of cities” between big and small cities, primary and would buttress our efforts to get this last secondary cities, industrial and commercial stage of urbanization right. cities. Importantly, the research provides little guidance regarding how we might intervene to improve our future cities to support sustainable serious limitations in our understanding of cities human habitation on the planet. and urban evolution. A new “science of cities” IN HIS 1937 ESSAY “WhaT IS A CITY?,” Lewis Mumford detect relationships among the potential The New Urban Agenda—to be announced in would buttress our efforts to get this last stage described an evolutionary process through which components of urban evolution, or offered October at the third UN-Habitat conference, in of urbanization right. the “badly organized mass city” would evolve into narrow prescriptions to fix one urban challenge Quito, Ecuador—will present consensual global I do not intend to present a new science of a new type of “poly-nucleated” city, “adequately while generating inevitable unintended conse- objectives for sustainable urbanization. These cities in this message. Instead, I will suggest a spaced and bounded”: quences that pose new challenges. This is objectives provide guidance for United Nations way to frame one that borrows from evolutionary because we have never developed a real science member states as they prepare for the gargantu- theory. The evolution of species is driven by four “Twenty such cities, in a region whose of cities. an task of welcoming 2.5 billion new urbanites to main forces, and it seems reasonable that environment and whose resources were For more than a century, planners, sociolo- the world’s cities over the next thirty years— corollary forces help to shape the evolution of adequately planned, would have all the gists, historians, and economists have theorized culminating the 250-year process through which cities. These forces are: natural selection, gene benefits of a metropolis that held a million about cities and their evolution by categorizing human settlement moved from almost entirely flow, mutation, and random drift. And they play people, without its ponderous disabilities: them, as noted by Laura Bliss in a well-docu- rural and agrarian to predominantly urban out in predictable ways that shape cities—where its capital frozen into unprofitable utilities, mented 2014 CityLab article about the likelihood contexts. But before we attempt to implement city growth replaces reproductive success as an and its land values congealed at levels that of an emerging evolutionary theory of cities. the New Urban Agenda, we must confront the indicator of evolutionary success. stand in the way of effective adaptation to They generated multiple typologies of cities, new needs.” from functional classifications to rudimentary From the medieval town hall of Mons, Belgium, the Guardhouse Monkey overlooks the city. Credit: © Jochen Tack / Alamy Stock Photo. taxonomies (see Harris, 1943, Functional For Mumford, such cities, designed with Classification of Cities in the United States; Angel strong public participation, would become the et al, 2012, Atlas of Urban Expansion; Knox, 2013, nuclei of new poly-nucleated metropolitan Atlas of Cities). But they based these classifica- regions that result in: tions on arbitrarily chosen categories and did little to inform our understanding of how cities “A more comprehensive life for the region, for became what they are or to presage what they this geographic area can, only now, for the might become. first time be treated as an instantaneous Even Jane Jacobs, in a foreword to her 1961 whole for all the functions of social exist- book, The Death and Life of Great American Cities, ence. Instead of trusting to the mere called for the development of an ecology of massing of populations to produce the cities—a scientific exploration of the forces that necessary social concentration and social shape cities—but provided only narrative drama, we must now seek these results accounts of what defined great cities, mostly through deliberate local nucleation and with regard to design, as part of her ongoing a finer regional articulation.” assault on the orthodox planning profession. In some of her later work, Jacobs set out principles Unfortunately, since Mumford wrote these to define great cities, based mostly on form, but words, we have not achieved poly-nucleated she never provided a framework to improve the cities or regions. Nor have we advanced a theory science of urban theory. of urban evolution. Urban theorists have de- Modern urban theory is plagued by several scribed cities, used basic pattern recognition to shortcomings. It is not analytic. It fails to provide 2 LAND LINES JULY 2016 3 Natural selection is a process of impulse and Drift describes the unpredictable ways that response. It relates to how a city responds to cities might change their character. changing external factors (impulses) that As noted, I do not want to lay out a new support or inhibit success. Impulses can be theory of urban evolution here. I merely want to economic, environmental, or political, but they recommend this direction in order to invigorate are, importantly, outside the control of the city. our thinking around urban change more rigorous- Economic restructuring, for example, might ly and systematically. A significant amount of select against cities that depend on manufactur- work has already gone into quantifying elements ing, have inflexibly trained workforces, or extract of this framework. Risk theorists and insurers or produce single commodities that face changes have quantified many of the external impulses in demand in global markets. Climate change and that challenge cities. Demographers and sea-level rise will inhibit the success of coastal population theorists have studied human cities or those exposed to severe weather events. migration, and macroeconomists have studied Political impulses might include regime changes, capital flows. A lot of attention has been paid to social uprisings, or war. Or they might be innovation and disruption in the last couple of something as seemingly minor as a change in decades. Random drift is a little less studied. But, allocation formulae for national revenues. as Bliss points out, big data and new technolo- Every impulse will benefit some cities and harm gies might help us to detect longer-term drift. In others. A city’s ability to respond to different any case, a larger framework that weaves these impulses might be a measure of its resilience, disparate areas of work together would advance which is directly influenced by the three other our understanding of urban evolution. evolutionary forces. On a cautionary note, while an evolutionary theory of cities would be a signal advancement of urban theory, it is useful to remember that, unlike Planners need better tools to drive their evolution, which is a mostly passive process— practices and to test their approaches. If we species enduring the external forces that act on them—cities, in theory at least, are driven by are to successfully implement the New Urban more purposive behavior: planning. But planners Agenda, a new toolkit based on evolutionary need better tools to drive their practices and to science would be hugely helpful. test their approaches. If we are to successfully implement the New Urban Agenda, a toolkit based on evolutionary science would be hugely Migration (gene flow) helps to diversify helpful. As Mumford concluded in his 1937 essay: the economic, social, and age structures of cities through the exchange of people, “To embody these new possibilities in city life, resources, and technologies. Presumably, the which come to us not merely through better in-migration of people, capital, and new technol- technical organization but through acuter ogy improves a city’s ability to respond to sociological understanding, and to dramatize external impulses. Out-migration, in general, the activities themselves in appropriate would reduce this ability. individual and urban structures, forms the Mutation, for cities, is an unpredictable task of the coming generation.” change in technology or practice occurring within a city. It might be shorthanded as innovation We at the Lincoln Institute of Land Policy or disruption. stand ready to support coming generations in Random drift involves longer-term changes in comprehensive and scientific analysis of urban cities that result from cultural or behavioral evolution and the important role that effective shifts. These might include decisions to maintain land policies can play in driving it. Our urban or preserve long-term assets, real or cultural. future depends on it. 4 LAND LINES.