A new study warns that 151 hydroelectric dams planned along six major rivers in the Amazon basin over the next two decades, including dozens of so-called mega-dams, could significantly disrupt the region’s ecological connectivity. Writing in the online journal PLoS ONE, researchers say 60 percent of the dams currently being planned would cause the first major break in river connectivity between the Andean headwaters and the lowland Amazon, possibly threatening the free flow of several Andean-Amazon rivers. The Andes provide most of the sediment, nutrients, and organic matter to the vast, species-rich Amazonian floodplain. The study also found the majority of the projects would increase forest loss because of new roads and transmission lines. “There appears to be no strategic planning regarding possible consequences to the disruption of an ecological connection that has existed for millions of years,” said Matt Finer of the Center for International Environmental Law and the study’s lead author.