"Dam-building spree pushes Amazon Basin’s aquatic life closer to extinction", 22 June 2023

...[A]...new study investigating how freshwater systems in the Amazon Basin are interconnected...

The rhythms of the waterways of the Amazon Basin, marked by low- and high-water periods, are vital to the health of the aquatic ecosystem, yet have been disturbed by a number of factors, such as a changing climate, deforestation, changes in land use, uncontrolled and disorderly urbanization, the expansion of roads, and the construction of dams...

...The authors identified 434 dams that have either been built or are currently under construction across the whole of the Amazon Basin, and a further 463 proposed dams that are in various stages of planning. In the worst-case scenario, in which all the dams currently proposed are built, 18 of the 98 free-flowing rivers classified by the study as either long or very long in length...would lose their status as freshwater connectivity corridors. This includes the Amazon River itself...

“If all the hydroelectric dams that are planned for the Amazon region are built by 2030, we’re going to lose almost all connectivity,” Paschoalini says. “Across every one of the rivers, the line starts to turn, if not red, then orange. And if not orange, then a little pinker. It goes on decreasing in the connectivity index, showing how much we are losing.”

According to the study, more than 20 species of long-distance migratory animals, as well as river dolphins, would be threatened by the construction of hydropower dams...