Liz Barreto Coelho Belém, Raquel Nieto, Leonardo F. Peres, Nilson Oliveira da Silva, Milica Stojanovic, Marta Vázquez, Ronaldo Albuquerque, Allan Arantes Pereira, Carlos C. DaCamara, Luis Gimeno, Ana M. B. Nunes, Letícia Couto Garcia, Geraldo Alves Damasceno Júnior, Fabio de Oliveira Roque, Renata Libonati
ABSTRACT In recent decades, the Upper Paraguay River Basin (UPRB) has experienced increasingly frequent and intense wildfires, often linked to severe droughts. While these events reflect broader hydrological imbalances driven by changes in precipitation and atmospheric moisture support, the role of moisture sources in modulating drought–fire dynamics remains unclear. This study addresses this gap by identifying key moisture sources for the UPRB and analyzing their shifts during extreme drought years coinciding with high fire. We assessed the drought–fire relationship through correlations between the Standardized Precipitation‐Evapotranspiration Index (SPEI) and burned area (1986–2018), selecting the top‐3 extreme drought years using the SPEI‐based rarity index (|R|), and using the Lagrangian FLEXPART model outputs to track changes in moisture contributions. Results reveal a strong SPEI‐burned area correlation, 2007, 2010, and 1999 being the top‐3 extreme drought years aligning with peak wildfire activity. These years exhibited notable shifts in moisture contributions, particularly with persistent negative anomalies during the dry‐season, reinforcing the occurrence of extremes. The most severe droughts were preceded by contrasting wet‐season moisture conditions and consistently followed by strong dry‐season deficits, particularly from key continental and ocean sources, contributing to drought intensification. While drought severity modulates wildfire risk, fire occurrence and extent also reflect the influence of multiple interacting factors. The findings highlight the importance of moisture source dynamics in shaping drought–fire interactions.