CLIMATE VARIABILITY AND AGROECOLOGICAL CHANGE IN THE CENTRAL PAMPAS OF ARGENTINA

Global warming is likely to alter natural and agricultural ecosystems, probably causing relocation of some of the major crop-producing regions, and a change in the geographic distribution of rangelands and forests. More important than the direct effect of the temperature increase, would be any alteration in the rainfall pattern in those many regions where rainfall limits crop production. The purpose of this work, which focuses on a traditional, semi-arid, cattle-cereal crop production area in the Central Pampas of Argentina, was to study structural and functional changes in this agroecosystem in response to the measured climate variability over a 30 year period, 1960-1990. Using long-term data, correlation analysis was used to estimate the degree of association between changes in the land use pattern on the one hand, and changes in rainfall, grain price and crop yield on the other hand. Crop yield was the result of an interaction between climatic and technological factors. The analysis also Linked climate variability with key agroecological factors such as hydrology, energy flow, and soil nitrogen balance. The results showed that changes in land use were highly correlated with the yield of crops, less correlated with rainfall, and poorly associated with crop grain prices. A positive correlation between the annual rainfall and the relative increase of the crop area was found for all districts analyzed. This change could largely explain the increased energy flow as well as nitrogen loss in the agroecosystem studied. Consequently, land use strategies should be considered with caution, especially during favorable climatic period in semi-arid environments. The same conditions that favor grain harvesting in these environments, may also set at risk the sustainability of a long-term, low-input agriculture.