Observational evidence of compensatory influences of deforestation on downwind precipitation in Brazilian breadbaskets

Abstract

Stable and predictable wet-season rainfall is crucial for soybean production in Brazil. However, climate and land-use changes, particularly Amazon deforestation, have increased rainfall variability in the region in recent decades. Here, we investigate long-term growing-season rainfall changes over two major soybean breadbaskets in Brazil from the perspective of atmospheric moisture transport. Utilising a novel moisture tracking framework based on a Lagrangian model guided by observations, we identify moisture source regions where evaporation contributed to rainfall over these breadbaskets. Furthermore, we quantify the relative contributions of source evaporation versus atmospheric (thermo)dynamics changes to downwind rainfall variability. Our results indicate that deforestation-induced evaporation declines have negatively impacted downwind rainfall in the breadbasket regions. However, strengthened circulation, evidenced by increased water vapour transport and low-level wind speeds consistent with decreased tree cover, has enhanced moisture transport from upwind regions (including Amazonia and the Atlantic Ocean) to the Brazilian soybean breadbaskets. This highlights the compensatory effects of deforestation on rainfall through decreased evaporation and altered atmospheric (thermo)dynamics, and how these effects may influence downwind soybean productivity in South America. Further understanding these interactions is critical for developing land management strategies to mitigate the agricultural impacts of climate change in the region.