Precipitation variability and landscape degradation in Río Negro (Argentina)

Using precipitation measurements from 12 meteorological stations and rectified NDVI values from GIMMS (AVHRR), this study provides information about the connections between precipitation trends/variability and degradation in southern Río Negro (North Patagonia, Argentina), after analyzing the behaviour of these two components separately. For the period 1972-2005 a significant precipitation increase was detected in two meteorological stations in the eastern part of the province. The Subandean vegetation district also presents a significant precipitation increase for the period 1982-2003. Precipitation amounts in the study region show both high seasonal and interannual variability. The interannual variability shows a significant positive trend in some meteorological stations in the south and west. Many annual precipitation anomalies were detected, but they could not be connected with El Niño Southern Oscillation or La Niña Southern Oscillation. Most regions show a decrease of the maximal NDVI for the period 1982-2003. The negative trend caused a mean decrease of 2.7% of the maximal NDVI in 22 years and could be taken as an indicator of degradation increase. In the central and eastern part of the study area there are significant positive correlations between the annual precipitation amounts and the maximal NDVI, indicating that part of the interannual NDVI variation can be explained by a linear dependence to precipitation. However anomalies of both quantities seldom coincide. The negative NDVI trend in the western and southern part of the region might be related to the positive trend of the interannual precipitation variability. This study suggests that land use strategies (and specially sheep numbers per hectare) have to be managed in a flexible way, in order to be adapted to precipitation amounts every growing season and the increasing precipitation variability in the future.