Environmental Externalities of Land Use

As a spatial structure, land use is linked to a number of externalities that impose significant economic, social, and environmental costs that communities are less willing to assume. This has led to various land use regulations, mostly under the umbrella of “smart growth” initiatives, to increase density and promoting modes other than the automobile. Strategic indicators that are recurrent in evaluating the environmental externalities of land use involve vehicle-mile (km) traveled, transit ridership, and average commuting time to the workplace, which are all spatial interaction variables.

The last half a century has been associated with a declining role of public transit, a more disorganized spatial structure, and the prevalence of suburbanization. This trend could be reversed with two possible and interdependent paths of land use changes unfolding, depending upon the concerned urban setting:

·         Densification. It involves a more rational and intensive use of the existing land uses to minimize the environmental footprint and the level of energy consumption. Initiatives such as smart growth are trying to change the urban planning framework towards forms and densities that are more suitable for walking, non-motorized modes, and public transit. If this occurs in proximity to a transit station, the term transit-oriented development is used to characterize the densification process. Yet this implies higher levels of capital investment and the provision of an adequate public transit service since, in a car-dependent context, densification easily leads to congestion and other externalities.

·         Devolution. Due to economic and demographic trends, several cities could lose a share of their population, imposing a rationalization of urban land uses. In industrial regions of Europe and North America, several cities have lost a share of their economic base and, correspondingly, their population. This involves dismantling urban infrastructure and closing sections or whole neighborhoods, leading to the emergence of urban forests and even forms of urban agriculture. Detroit is a salient example since the population of the city dropped by more than a half from 1.8 million in 1950 to 713,000 in 2010. Yet, the population of Detroit’s metropolitan area has remained relatively stable since the 1970s, hovering around 4.2 million. This implies that the process of devolution is very location-specific.

What could shape land use towards a more environmentally beneficial structure in the future is uncertain since many policies appear to be not particularly useful. Since it took 30 to 50 years for North American, Australian, and to some extent, European cities to reach their current patterns of automobile dependency, it may take the same amount of time to reach a new equilibrium if specific conditions apply. This transition could even be more complex in developing economies where the forces of motorization are gaining momentum with economic development. Since the price of energy is an important component in the cost of personal mobility, energy costs are likely to be a significant force shaping urban development. If the energy component does not change significantly, congestion and infrastructure capacity limitations will likely play a more important aspect. Consequently, the environmental impacts of transportation and land use are likely to stay prevalent for several decades.