Scientists say the cause may lie high above the rainforest, where invisible “flying rivers” carry rain from the Atlantic Ocean across South America. “If you break that pump by cutting down too much forest, the rains stop reaching where they need to go.”What are flying rivers and how do they work? That’s important because the Amazon rainforest is a vast storehouse for the carbon dioxide that largely drives the world’s warming. During the dry season, flying rivers sweep across southern Brazil before reaching the Andes — precisely where deforestation is most intense. Forest makes a fragile pumpMAAP researchers found that rainfall patterns depend on when and where the flying rivers cross the basin.