Changes in the aridity index across Brazilian biomes

The increase in aridity has been reported in different regions of the world in recent decades. This study analyzes changes in aridity in Brazil over the period 1961-2020, both in terms of their spatial distributions and across different main Brazilian biomes, using the index recommended by the desertification convention applied to a high-resolution observational gridded dataset. Results revealed a trend towards drier conditions in the center and northeast of the country, while the southern region showed changes to wetter conditions. Over the study period, an expansion of semi-arid areas at the expense of dry subhumid and humid regions was observed. These trends accelerated over the period 1991-2020, indicating an intensification. In this period, an area of >4200 km² within the arid category was observed for the first time according to the convention classification. In addition, novel areas, with sizes ranging from 1200 to 11,500 km², included in the dry subhumid category were detected in the center of Brazil. Moreover, all the scenarios revealed by the observations are fully consistent with the projection of future climate change. Regardless of the observed trends in aridification, a preliminary analysis based on the time series of the vegetation health index (VHI) shows negative trends in all Brazilian biomes, suggesting an increase in vegetation stress. Current trends may significantly impact the country's economy in the near future, affecting production systems, including agricultural activities and the availability of water resources for multiple uses. This study points out areas in the country that should be prioritized in soil and vegetation recovery actions and regional environmental development policies.