Building the 428 hydroelectric dams proposed for Brazil's Amazon basin – three times the existing number – would devastate the environment and could even disrupt regional weather, an international team of researchers warned on June 14.
Writing in the journal Nature, the scientists unveiled a Dam Environmental Vulnerability Index (DEVI) to score the impact of these future dams across a broad range of criteria and help policy planners decide which ones to leave on the drawing board.
"We have to put the risks of the table and change the way people are looking at the problem," said lead author Edgardo Latrubesse, a professor at the University of Texas at Austin.
"We are massively destroying our natural resources, and time urges us to find some rational alternatives for preservation and sustainable development."
The network of rivers flowing into the Amazon River is the largest in the world, and nourishes the planet's highest concentration of biodiversity.
Damming these enormous tributaries – sometimes dozens of times – blocks nutrients that nourish downstream ecosystems, floods huge tracts of forest, and threatens both aquatic and terrestrial wildlife.
The new index grades dams from 1 (benign) to 100 (highly destructive), and can also be applied to existing structures.
Two huge dams, for example, recently built on the Madeira River, home to the most diverse fish population in the Amazon system, earned alarmingly high scores due to the potential for erosion, runoff pollution, and trapped sediment.
There are plans for the construction of an additional 25 dams further upstream on the Madeira.
Massive dams, massive destruction
Worldwide, there are more than 58,500 large dams at least 15m from foundation to crest, or impounding at least three million cubic metres.
China alone has 40% of the world's large dams.
Add those in the United States and India, and that percentage rises to two-thirds, according to the International Commission on Large Dams. – AFP Relaxnews