The BR-319 roadway is a mostly dirt road through the rainforest that connects the states of Amazonas and Roraima to the rest of the country. It ends in Manaus, the Amazon’s largest city with more than 2 million people, and runs parallel to the Madeira River, a major tributary of the Amazon River. The Madeira is at its lowest recorded level, disrupting cargo navigation, with most of its riverbed now endless sand dunes under a sky thick with smoke.