Satellite-based assessment of Amazonian surface dryness due to deforestation

ABSTRACT Intensive deforestation due to human activities has been occurring in the Amazon over the last several decades, leading to a projected decrease in precipitation due to reduced evapotranspiration (ET) according to the prediction by climate model experiments. Such hydrological and climatic changes are closely related to the drying of soil moisture (SM) as a source of atmospheric water vapour via evaporation. We used a satellite-observed index, temperature-vegetation dryness index (TVDI), to assess the impact of deforestation on SM during the dry season. Thirteen-year (2002-2014) data for three representative areas (forest, deforesting and deforested) in the Rondônia, southwest (SW) of Amazon were used to evaluate the relative changes in SM corresponding to the extent of deforestation. We found the increase in dryness in the deforested Amazon using the moderate resolution imaging spectroradiometer (MODIS) satellite sensor. Furthermore, given that the impact of forest removal on surface SM can be distinguished from the associated changes in precipitation and vegetation conditions, it is found that the relative proportion of deforested areas is linearly correlated with that of SM. The results from this study are useful to validate climate model simulations of deforestation and to improve our understanding on the biophysical controls of Amazon deforestation.

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