摘要：The need for maintaining the properties of the ecosystems within certain ranks of variation precedes the concept of sustainability. Argentine farming activity has remarkably grown and transformed in the last 20 years. The technology of production has significantly changed and this technological growth was accompanied by a remarkable expansion of the agricultural border towards diverse extrapampean zones and by an increase of the agricultural component of the agricultural-cattle rotation in the Pampean region, with the consequent movement and intensification of the cattle activity towards marginal zones and confined systems. The objective of this article is to develop some basic elements of Ecology that concern to the problem of the sustainability of farming ecosystems and to call the attention on the most relevant environmental problems of agriculture in Argentina. The stability of the operation of an ecosystem increases with its diversity. This behavior of the ecosystems is known as "portfolio effect" for its similarity with the behavior of investment strategies. The ecosystems are regionally connected by diverse mechanisms that include the transport of materials and energy through long distances and the migratory movement and dispersion of organisms. As a frequent result, what happens in an ecosystem bears consequences on another one. Many environmental effects of the farming activity are little significant at the farm scale, but, when added, they can have repercussions in other ecosystems, like lagoons or estuaries, or in components of regional or global nature like underground water or the atmosphere. In agroecosystems, management attempts to lead solar energy towards certain plant or animal products. The energy of subsidy contributed by the farmers in extensive systems is relatively small in comparison to the income of solar energy, but at the same time it is an important proportion of the energy obtained in the product. Agroecosystems show large environmental heterogeneity and complex seasonal and interannual dynamics. Although part of this variation is perceived and taken care of with much attention by technicians and farmers, its complex nature frequently results in some aspects being unnoticed or not receiving suitable treatment. The potential environmental problems related to the Argentine farming activity are very numerous and of diverse nature. An informal consultation among colleagues threw quite coincident answers emphasizing the contamination by fertilizers, pesticides, and waste material from confined animal production systems as the main problems. Also they were worried by diverse manifestations of soil degradation, such as loss of organic matter and nutrients, soil erosion, and the loss of diversity at different scales.
