The Dry Chaco is a semi-arid ecoregion in South America, covering parts of Argentina, Paraguay, and Bolivia. To date, the region hosts one of the largest dry forests in the world. Since the 1980s, the region has been characterized by large-scale deforestation for soybean production and intensive cattle ranching. The potential impact of these newly established agricultural land on the surrounding environment is of great concern. Recent studies have shown that deforestation leads to changes in the hydrological cycle. At several locations in the Chaco, farmers have also reported severe salinization of their fields several years after deforestation. However, the impacts of deforestation on the water balance and soil salinity at a regional scale are not entirely clear. The overall objective of this work is to better understand the spatio-temporal patterns of soil hydrology and salinity in the Dry Chaco using land surface models, satellite data, and experimental field measurements of soil salinity.

Three different land surface models were used to gain insight into the hydrological impacts of deforestation. Because most models use climatological vegetation data and static land cover parameters, they lack the ability to accurately represent the ongoing land cover changes in the Dry Chaco. Therefore, land cover changes were implemented using time-varying satellite-derived vegetation indices together with annually updated land cover information. Our results show that there are large regional and long-term differences in the simulated water budget components among the three models. The three models also redistribute water differently in response to the updated vegetation and land cover treatment.

This study also shows that there are large regional differences in soil salinity across the region. Natural soil salinity is strongly correlated with climatic and topographic gradients in the region. The most saline soils are found in the drier parts of the Chaco with shallow groundwater tables. These areas are prone to severe soil salinization after deforestation. In the wetter parts of the Chaco or in areas with deep groundwater tables, the risk for severe soil salinization is relatively low. The results of this study can provide a basis for further research on the spatial variations of soil salinization in dryland ecosystems and support the development of appropriate land use planning.