The 2023 Manaus smoke crisis and the role of highway BR-319 in a new Amazon fire cycle

In 2023, Manaus—the largest city in the Brazilian Amazon—experienced a severe smoke crisis linked to forest fires, extreme drought, and advancing deforestation. Using satellite imagery, atmospheric data, and field observations, we identified the municipalities of Manaquiri, Careiro and Autazes, along the BR-319 and AM-254 highways, as the primary sources of PM2.5 emissions. These fires, fueled by weak environmental governance and infrastructure-driven deforestation, led to PM2.5 concentrations exceeding 314 µg/m3—more than 20 times the WHO limit. Our results show that plans to reconstruct BR-319 threaten to accelerate unsustainable land-use transitions, intensify fire outbreaks, and compromise climate stability, biodiversity, and public health. The findings highlight the environmental infeasibility of expanding road infrastructure in this region and call for alternative development strategies. Promoting low-impact options such as improved fluvial transport is essential to safeguard biodiversity, climate stability, and public health in the Amazon.