The boundaries of the transformed human territory are often diffuse and complex. It is said that the city is a cultural and social construction that, when it does not face any physical limit, tends to grow unlimited as a city sprawl, taking up and transforming the territory around. However, at least as far as we live in european cities, the city sprawl should not be understood as a consequence of supplying new housing for a growing urban population but as the result of an instant economic exploitation of the territory which distorts the relations between the closer agricultural space and the city: the structure of the city becomes less dense and compact, and the journeys, times and the distances between uses are increased. Because of that, it is much harder for the citizens to use streets, squares or any other kind of public space effectively as a meeting area.

The image above shows the urban area of Santander in 2001, when according to the numbers obtained from the INE (the Spanish Statistics Institute), the city housed 185.231 people in 81.737 homes (there was 2,26 inhabitants per dwelling).

When this orthophoto was taken in 2011, Santander was housing 178.095 inhabitants in 92.423 homes (1,93 inhabitants per dwelling). And going back to the past, there were 196.218 people in 72.029 dwellings in 1991 (2,72 inhabitants per home). According to this urban evolution, Santander has lost 18.123 inhabitants in the last 20 years but the number of dwellings has increased by 28% in the same period. Simultaneously, the number of occupants of the dwellings has decreased by 30%: if the occupancy rates in 2011 had been the same as in 1991, the number of inhabitants would have reached 251.390. But the urban growth has only transformed into urban plots a great part of the agricultural land that the city still had in the rural neighbourhoods of San Román, Monte, Peñacastillo, Nueva Montaña and Adarzo. As a result of this, the distances and the movements in the city has also lengthened.

Is it possible to control the cities’ urban growth and densify the urban fabric while keeping the quality of the public spaces and providing new services to the citizens? Yes, but only if the agricultural land that circles the european cities is preserved: in the western societies, with low population growth rates, there is no reason for this urban sprawl apart from the speculative housing market. The agricultural land, useful and valuable for both local food production and support of the ecological process between the city and its environment, is very vulnerable. The erosion of rocks has slowly created superficial layers of topsoil, through the simultaneous action of water, temperature and wind. After starting the chemical process for rock weathering, eroded sediments are naturally transformed into productive soils by small organic beings like little plants, microorganisms and earthworms.

Generally, this land is not protected and is expected to be transformed, except when some ecological, cultural or productive values make it unique and important for the society: land at the boundaries of a city is rather inexpensive and accessible, well connected to the inner urban fabric but more vulnerable to the urban transformations. At the same time, it provides the society with food and resources and is part of the development of a culture based on the exchange of products.

The agricultural belt has been essential in the cities’ success since their birth during the Neolithic –Çatalhöyük, in Anatolia-: it fed the cities of the old great civilizations –Emerita Augusta or Cuzco-, was essential for the new settlements founded by the global empires in the Modern Age –Lima-, and was one of the main elements in which the new Urbanism developed by the utopians -Saint-Simon, Fourier, Godin or Howard- was based to resolve the unhealthy conditions of the 19th century industrial cities –the garden city movement-. Today, the preservation of the agricultural land is one of the most important challenges that must be dealt with by a sustainable urban planning which focus on the territorial management: the agricultural belts and the green infrastructures are some of the tools that could make compatible the urban growth with the agricultural production, the leisure areas and the green tourism to assure the future and the dynamism of the city.