Climatic change and El Niño-La Niña periodicity related to deforestation, land degradation and sustainable management in sub-tropical regions
|Location||International Geological Congress,oslo 2008|
|Author||Busnelli, José; Sayago, José Manuel; Neder, Liliana; Collantes, Mirian Mabel|
|Holding Date||03 September 2008|
The evidence of the Climatic Change is clear when analyzing the temporal and spatial registers of rains and temperatures. This climatic change generates geomorphologic process which in addition to uncontrolled human practices leads to degradation of soils on broad agricultural lands provoking a high problem to the productive activities which are one of the most important economic incomes. The study area belongs to the Western Chaco Plain in the subtropical region of Tucumán Province, Northwestern Argentina. The aims of this work were -Analysis of the multiannual climatic changes according to historical pluvial variations in the last 30-50 years. -Evaluation of the deforestation rates and agricultural land incorporation. -Mapping hydric erosion intensification. -Study of productivity decrease in soils according to the diminishment of organic matter and interchange cationic capacity and increase in soil compactation. These data were correlated with "El Niño-La Niña" phases of ENSO in order to obtain soil degradation hazard maps and drought-flood scenarios. It was recognised a great jump (25%) in the historical average pluvial record since 1970. This pluvial increment corresponded with increasing deforestation of lands formerly covered by the Chaco forest changed into farming areas. In this way the natural Chaco forest which occupied 70 % in 1970, it just covered 10 % in 2003. It was found that when the longer the time since deforestation, higher chemical, physical and biological soil degradation (as outstanding results were found that the organic matter decreased 35 % in the first 5 years since deforestation and then 48 % when the time is major to 28 years). The rainfall erosion is also increased after deforestation (sheet flow erosion increased 46 % and gully and ravine erosion 78%). The modeling of agricultural hazard was developed taking into account "El Niño-La Niña" of ENSO occurrence, which take place on southern paciphique ocean influencing th atmosphera-ocean circulation on global scale. It was detected a drought related to El Niño (1997-98) which was taken as an extreme scenario of dry condition and an abundant storm period during La Niña (2000-01) took as the scenario of extreme wet condition. As a conclusion this study would allow to improve management programs for agricultural practices in the region in response to drought or wet seasonal periods controlled by El Niño-La Niña Phenomena. Sustainable management planning would be carried out with anticipation of months using the data obtained by the monitoring and forecast of the temperature in the subtropical South Hemisphere Pacific Ocean.