In this paper I will focus on the environmental damage caused by horizontal urbanization.
An increasing number of studies point to a clear relationship between human population density and energy consumption: the latter increases as population density decreases.
The same occurs with carbon emissions and other atmospheric contaminants. Urban land development directly impacts the environment. Urban ground cover leads to a decrease in the ground’s ability to store carbon and accelerates water circulation, which may result in flooding caused by rainwater run-off.
Some areas are equally susceptible to natural disasters, such as flooding caused by overflowing rivers as well as soil contraction and expansion, which can produce cracks in man-made constructions.
Urban land development affects plant and animal biodiversity, both directly through the disappearance of species, as well as indirectly through the fragmentation of their habitats. The discontinuity of ecosystems, which impedes populations from mixing, impoverishes the genetic diversity of species thus making them more vulnerable.
One can easily observe the gardens found in single-family homes or townhouses being filled with exotic plants as per the current fashion, such as we have seen with palm and olive trees.
On the other hand, the extension of the horizontal construction contributes to the disappearance of agricultural areas. It is worth noting that, historically, cities were built in the most fertile regions that could be easily irrigated and easy to exploit in terms of agriculture. Although this exploitation has been substituted by another way of life, urban sprawl continues to result in the distancing of agricultural areas from, and the subsequent environmental degradation of, urban areas. Marshlands are drained, and the beds of smaller waterways are altered.
In neighboring countries like France, the increase in developable land in the countryside has grown quickly and intensely over the last 20 years.
Horizontal expansion has given rise to new landscapes. Today one finds large expanses of single-family homes and an all new range of architecture, plant and animal life, and new standardized features – all of which is more reminiscent of a lifestyle transformation in the periphery of the city than in a lamentable loss of character in terms of identity or heritage.
In the cities of the United States and Canada, we see two completely opposite models of urbanization. On the one hand, we find city centers featuring vertical design, and on the other, the suburbs with large expanses of horizontally urbanized land. These cities have excellent means of public transport, and in Manhattan residents walk many kilometers each day.
An increasing number of architects and urban planners are calling for a more intensive model of urban development: skyscrapers in city centers that provide lower energy costs.
The suburbs of these cities are immense in terms of the extension of their row houses. There is no city center. Residential areas are built, and for every x number of residents a commercial and leisure area is constructed, along with schools, hospitals, cultural centers and religious institutions. As a matter of fact, suburban families tend to own two or more cars, depending on the number of family members there are in a given household.
Studies point to a twofold increase in fuel expenses and the resulting CO2 emissions (and its greenhouse gas effect) in suburban areas.
Horizontal urbanization also contributes to global warming due to the difficulty of thermally insulating single-family houses, and energy loss is also higher in such homes due to greater exposure to the outside environment.
There are two types of horizontal urban expansion: One originates in the countryside, while the other is rooted in the city’s peripheries.
We are seeing how urbanized areas are growing around smaller towns and cities, as well as along the highways that connect them. Here we find single-family homes and smaller housing developments. In the city’s periphery, meanwhile, we find land that was once used for farming being developed for housing.
This phenomenon alters the landscape of the towns and cities. The architectural models are repeated to the point of banality. These new spaces become increasingly farther removed from the city center, creating an identical suburban area with roundabouts, calibrated and artificial roads, treated and uniform vegetation, and large commercial-area parking lots. This pattern is repeated in accordance with the spatial distribution from one community to another. The multiplication of infrastructures and residential areas contribute to this landscape continuity.
The influence of natural characteristics, such as vegetation, topography, geology, hydrology – along with the presence of agricultural spaces and their multiple combinations, associated with the forms and limits of urbanization – allow for landscape configurations that are relatively diverse within the monotonous spaces.
This horizontal expansion also produces social division and increases the cost of the infrastructure needed for the development and maintenance of new urbanizable areas.