In January 1852, when the Grand Army was advancing toward Buenos Aires to put an end to Rosas's protracted tyranny, he tried to stop it by burning the dense thistleries covering the countryside. The fires were put out by rain, and the battle of Caseros resulted in his ousting from power. The use of the environment for military purposes is as old as war itself and is a manifestation of the influence of man on the environment. Rural production also affects and is affected by the environment, but changes – unlike those introduced by Caseros – are only perceptible in the long run. This chapter deals with the environmental conditions of production, that is, how an environmental factor determined the pattern of rural production in nineteenth-century Buenos Aires.

Environmental changes are triggered by natural phenomena (climate variations, volcanic eruptions, earthquakes, droughts, floods) but also by the action of men and beasts. Men and beasts, in return, are affected by the transformations of the environment that their actions cause. War, conquest, trade, and migrations have been fundamental factors in the dispersion of plants and animals. The potato, a native of the American continent, which transformed eating patterns and habits in Europe, is one of the bestknown cases. The repeated failure of its harvest in Ireland in the 1840s provoked a famine but seems to have been a crucial element in that country's eighteenth-century population revolution. The expansion of phylloxera in Europe in the 1870s is another example of the consequences of human action on production. Carried by Californian vines, the parasite almost completely destroyed the European vineyards.