The Place of Nature in the Metropolis

Plano C, 2014
Area Planning Urban Development Medium Information Visualization Type Research

Porto Alegre, Brazil?s southernmost capital, had, through the last 50 years, a tradition in environmental management to be proud of. The city published an Urban Environment Atlas, created the Participatory Budget, and destined 24% of its territory to specially protected areas. In the last 10 years, however, the municipality grew to neglect the environmental question, and we watched the slow dismantlement of the ideas that molded the city once recognized as Brazil?s greenest capital.

Porto Alegre?s form and development were, from the start, deeply connected to the landscapes and scenic beauties available (CABRAL, 1978), from the beaches to the hills and now towards the bucolic landscapes currently occupied by rural dwellers. This occupation would be initially lead by the wealthy, which in time ended up bringing the infrastructure that would allow the later occupation of poorer populations. This effect can be observed today in the southernmost portion of the city, once known as the rural zone of Porto Alegre, by luxury condos that carry along with them major urban equipments and mega-infrastructures.

To completely understand what this occupation means, the method described by McHarg (1969) is applied. The main atributes, that promote greater value to human occupation when left untouched, were superposed : inundation zones, wetlands, aquifer recharge zones, strong slopes, protected areas, forest patches, agriculture adequate soils, and airport influence areas.

In this exercise, one must assume that ecosystem services represent an impossible-to-calculate value. Secondly, if something represents a value, by logical deduction, it must also represent a cost to its users if it were to be destroyed. To calculate this cost without numbers, the same value is addressed to every land atribute, applying the same color and opacity to each one of them.
From this color shift, an Urbanization Cost Map can be obtained, in which the darkest areas represent those that support most ecosystem services (provision, regulation, culture and support). When this information is confronted with the roads planned by the city hall and future allotments, one must come to the conclusion that the urban expansion is taking place precisely on the city?s most environmentally relevant areas.

Besides the information provided by this analysis, one must consider as well that the city has today a habitation deficit of 38 thousand families (living in extreme poverty conditions), and at the same time there are 48 thousand vacant apartments and houses in the inner portion of the urbe. Its Form Index is of about 0.47, which indicates a very inefficient occupation; and the projected densities in the regulating plan, apart from being low, are not practiced by most of the neighborhoods.
Taking all in account, it goes without saying that a more compact occupation model is urgent in Porto Alegre. This compacity, however, has its advantages and disadvantages. On one hand, scale economies can be obtained - concentration of jobs, greater competition, better quality services-, on the other hand, already existant negative externalities might be enhanced. During the last 5 years, the city was included in the list of municipalities in critical situation regarding the Industry Potencial Pollution Index. The water from its main drinking water source, the GuaĆ­ba Lake, is found heavily polluted by domestic and industrial wastewater, and high temperature records are beaten every year. Last but not least, in 2007, the city had doubled the pollution level recommended by the World Health Organization, obtaining, with this, the title of Brazil?s second most polluted capital.

From this insights, one might deduce that as the degree of compacity grows, both the scale economies and the negative externalities curves go up. This suggests that, at some point, one should find a limit degree of compacity; everything beyond this point causes more prejudice than earnings for the city. The ?antidote? for these negative externalities are known as innovation technologies, or sustainable urban systems, such as parks and green-blue infrastructures. This project aims to determine if the application of said systems is possible to be retroactively applied to Porto Alegre?s infrastructure systems.



  • BACCHIN, Taneha K. TU-Delft