400+ dams could irrevocably harm Amazon ecology — but solutions exist

Dams and reservoirs affect fish and other riverine fauna by creating barriers to movement, both upstream and downstream. Many fish in the Amazon migrate thousands of miles as part of their life cycle, a journey that can involve complex patterns of movement through river flows and flood plains. Migrating fish often move upstream from black-water and clear-water flows in the Amazon Basin to spawn in whitewater reaches in the Andean headwaters. In Brazil, the list of fish that make this journey includes most, if not all, commercially valuable species, in terms of nutrition and economics, such as the tambaqui (Colossoma macropomum) and giant catfish (Brachyplatatystoma sp). Fish that can’t migrate could go extinct, with a predictable effect on the biodiversity — and the economic viability — of the world’s largest river basin, says Elizabeth Anderson, director of international research programs for the School of Environment at Florida International University. “This is globally important from a conservation perspective.” A free flowing Amazon river system will help guarantee the well-being of the region’s aquatic wildlife and the stability of freshwater commercial fisheries. Photo by Peter Angritt licensed under the Creative Commons Attribution-Share Alike 4.0 International license. Location makes a difference. Dams built in the lower stretches of a river system generally need large reservoirs to create a dependable year-round source of water pressure to drive electric turbines. Dams higher in the headwater portion of a river system have the advantage of steeper gradients, and some designs work with…