El impacto de la ganadería y la agricultura en los ecosistemas terrestres.-Desamortización e intensificación agraria de riberas fluviales: La vega de Aranjuez

Abstract

ABSTRACT In Spain, successive appropriations by the state of river flood terraces which had previously been in communal or private hands led to –apart from notorious social repercussions– increased pressure on the limited water resources, loss of the diversity of agricultural uses as practices became more uniform, and accelerated destruction of the few remaining fragments of riverside woodlands. Later water laws (1866 and 1879) and court rulings permitted the aggregation of adjacent fields on river margins, the disappearance of customary uses (including settled and transhumant grazing) and the expansion of horticulture and other intensive arable crops. These changes in the middle of the nineteenth century provoked the loss of vegetation that, till then, had acted as a brake on the movement of peak flood flows whilst also flattening these peaks. This paper analyses the changes in a section of the Tajo-Jarama river valleys based on historical maps, and the IGN map series. The data show how the rate of change from natural terraces to cultivated terrain varied for different areas but was practically complete everywhere in the twentieth century. The model presented may be extrapolated to other rivers in the Iberian Peninsula indicating a process that could be relevant, together with other factors, in the interpretation of the magnitude and intensification of floods registered on the major rivers between the end of the nineteenth century and the beginning of the twentieth.