The question posed above has been much debated and discussed by researchers, policymakers and the general public. The conventional wisdom on this subject is that with a few exceptions, the impact of cities on the environment is malign. In fact, most people seem to think that cities are hot spots for ecological damage, that they are severely polluted and polluting, and that they are particularly at risk from natural hazards.
Although these beliefs make up a significant part of what we might call the "anti-urban credo," do they withstand careful scrutiny? As new research by the geographer William Meyer and others shows, the perspective that holds urbanization's effects are necessarily bad is problematic if not altogether false. Why might this be the case? Let us investigate.
This new research clearly suggests that increasing urbanization does not necessarily lead to greater ecological damage. To comprehend this point, note that if we keep the human population of a certain size fixed, then an urban, high-density way of life is more conservationist in terms of residential land use than a suburban or rural way of life. In other words, by concentrating human impact in a relatively small area, cities contain it.
This kind of positive environmental effect has been found in less-developed nations as well. In particular, recent empirical research has used the metric of deforestation to show that rural population growth-not urban population growth-is positively associated with deforestation.
Many readers are likely to believe that relative to rural areas, urban areas are more polluted and polluting. However, recent research shows that given the same living standards, the city pollutes far less on a per-capita basis than does the countryside. To further buttress this point, consider the consumption of fossil fuels. Once again, research shows that at least in the developed world, there is a distinct urban advantage in the consumption of fossil fuels and hence an urban advantage in reducing greenhouse gas emissions.
What this means is that to the extent that urbanization lessens energy consumption and deurbanization increases it, the former will diminish and the latter will worsen energy-related emissions that give rise to many kinds of pollution. The policy implication is that when contemplating whether urban areas are necessarily more polluted and polluting than rural areas, the disadvantages from concentrating harmful activities spatially must be weighed against the advantage of diminishing their range and perhaps their total magnitude.
What about natural hazards? The prevalent view is that city growth magnifies the dangers from natural hazards. However, until very recently, too little attention has been paid to the ways in which the defining attributes of cities can lead to greater safety and not greater danger for city residents. For instance, urban residents are frequently less vulnerable to natural hazards as compared to rural populations. In addition, it is important to understand that it is unhelpful to suppose that urbanization intensifies the net impact of natural hazards by putting large numbers of people in harm's way. What is more likely is that urbanization diminishes the impact of natural hazards by putting people-much more effectively than a dispersed settlement pattern would-in help's way.
The central point made by this new body of research is easy to grasp. First, larger urban areas tend to have larger problems in absolute terms. To make meaningful comparisons, therefore, one must correct for population size to accurately assess how much impact a person will have or how much safety a person will enjoy in an urban or a rural setting.
This favorable report on the environmental effects of cities does not mean there are no problems associated with urbanization. Secondary urbanization-the spatial dispersion of populations and the political fragmentation of metropolitan areas-and its environmental impacts are things to worry about for city authorities and urban planners.
Amitrajeet A. Batabyal is the Arthur J. Gosnell professor of economics at Rochester Institute of Technology, but these views are his own.
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