[en] The fundamental objective of this thesis is setting up a model to optimize the functioning of agricultural activity at the landscape level. It is a thesis with a strong methodological component. However, to base how the functioning of agrarian systems would have to improve their efficiency in the use of natural resources, as well as their organic logic, I base myself on the study of agrarian systems in historical perspective. Thus, in the first three chapters of this doctoral thesis I analyze the socio-metabolic transition from organic to industrial agriculture using the methodology of social metabolism and the analysis of material and energy flows (chapter 2) as well as incorporating the analysis in terms of landscape ecology (chapter 3) and food systems analysis (chapter 4). I apply it for a case study located in the Catalan pre-littoral Mediterranean (the historical region of Vallés), in three different historical moments: i) around 1860, in a context of viticultural specialization and in full development of agrarian capitalism; ii) in 1956, just at the time of the departure of the autarchic period in Spain and in a transition prior to the Green Revolution; iii) in 1999, after the Green Revolution and in a situation of livestock specialization, derived from the integration of local agriculture in the global regime. Once the keys to the functioning of the agrarian systems prior to the green revolution have been identified, I have laid the foundations for the second part of the doctoral thesis. In it I propose first (chapter 5) the theoretical development of an optimization model that allows us to analyze what would have been (or could be in the future) the most optimal functioning of the various assets of agroecosystems that allow to meet certain objectives social. In chapter 6 I apply this model in the case of Sentmenat (El Vallès) for 1860, to see what would have been, in a context of non-existence of inequality, the best way to have organized the territory in order to meet different objectives: minimize the amount of surface needed per family, minimize the amount of work required, or deepen the specialization by maximizing the amount of vineyard that existed in the territory and could be maintained in a sustainable manner. Finally, chapter 7 is dedicated to applying the model again but at a prospective level of future agroecological scenarios. This allows us to characterize the limits of agroecological landscape strategies, basically due to the prevailing condition of closing the nutrient cycles. In spite of this, if a rational use of the nutrient stocks of the soil were made, it would be possible to reach sustainable population densities of up to more than 150 people / km2 with a depletion horizon of the phosphorus stock of about 1000 years. In addition, we verified how the current diet strongly limits the sustainable population density (around 70 people / km2) due to the high consumption of animal products. Thus, following a Mediterranean diet, which allows a balance between the wills of the consumer and the capacity of the territory, would achieve levels of satisfaction of much higher needs. Lastly, the strategy of maximizing production instead of meeting local needs could allow an increase of up to 30% in the final product (in terms of metabolizable energy). With this, we consider that this new proposed methodology opens a new tool that facilitates these social debates, taking into account the complexity of the functioning of the agrarian systems and without trying to simplify them to purely technical decisions.

[es] El objetivo fundamental de esta tesis es la generación de un modelo de optimización del funcionamiento de la actividad agraria a nivel de paisaje. Se trata de una tesis con un fuerte componente metodológico. Sin embargo, para fundamentar cómo tendría que ser el funcionamiento de los sistemas agrarios para que mejoraran su eficiencia en el uso de los recursos naturales, así como su lógica orgánica, me baso en el estudio de los sistemas agrarios en perspectiva histórica. Así, en los tres primeros capítulos de esta tesis doctoral analizo la transición socio-metabólica de las agriculturas orgánicas a las industriales haciendo uso de la metodología del metabolismo social y el análisis de flujos de materiales y energía (capítulo 2) así como incorporando el análisis en términos de ecología del paisaje (capítulo 3) y de sistema alimentario (capítulo 4). Lo aplico para un caso de estudio situado en el pre-litoral mediterráneo catalán (la comarca histórica del Vallés), en tres momentos históricos distintos: cerca de 1860, en 1956 y 1999. Una vez identificadas las claves del funcionamiento de los sistemas agrarios previos a la revolución verde, he sentado las bases para la segunda parte de la tesis doctoral. En ella propongo en primer lugar (capítulo 5), el desarrollo teórico de un modelo de optimización que permite analizar cuál hubiera sido (o podría ser en un futuro) el funcionamiento más óptimo de los distintos bienes fondo de los agroecosistemas que permitan satisfacer determinados objetivos sociales. En primer lugar lo aplico como análisis contrafactual de las posibles configuraciones del territorio bajo un contexto de desigualdad en las agriculturas orgánicas avanzadas, para 1860 (capítulo 6). Posteriormente se aplica a nivel prospectivo de futuros escenarios agroecológicos (capítulo 7). Esto nos permite caracterizar los límites de las estrategias a nivel agroecológico de paisaje, básicamente debidos al condicionante imperante del cierre de ciclos de nutrientes. Con ello, consideramos que esta nueva metodología propuesta abre una nueva herramienta que facilite estos debates sociales, teniendo en cuenta la complejidad del funcionamiento de los sistemas agrarios y sin pretender simplificarlos a decisiones puramente técnicas.