Wildlife in Amazon rainforest

Damming the Amazon may cause ‘profound’ damage to environment, study says

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An international team of researchers studying the effects of building hundreds of hydroelectric dams in the Amazon River Basin have concluded that the construction could result in environmental damage on an enormous scale.

The Amazon and its watershed is the largest river system on Earth, covering nine countries. Due to a desire to provide renewable energy for the region without the drawback of carbon emissions, plans are under way to add hundreds of hydroelectric dams to the system.

A total of 428 dams could eventually be built through the system, and a third of these are already built or under construction.

According to the researchers behind the study, insufficient attention may have been paid to the environmental disruption that the dams could cause to the whole system.

“The Amazon is the most important river basin on the planet. It’s a microcosm of our issues of today involving environmental, energy and health of the planet,” said Professor Victor Baker, co-author and professor of hydrology and atmospheric sciences at the University of Arizona.

According to Professor Baker, while consideration has been given to parts of the river in the immediate vicinity of the dams, the river system cannot be “separated out” into individual pieces. A large-scale assessment of how the dams would affect the entire Basin was necessary, the researchers concluded.

To draw up a large-scale picture of the potential disruption the damming could cause, the researchers developed a ‘Dam Environmental Vulnerability Index’ to quantify their assessment of possible damage. The index varies from 1 (most resistant) to 100 (most vulnerable).

It incorporates the potential for erosion, changes to sediment deposition, impact on food supply, land use changes, runoff, and effects on biodiversity.

Rivers in the Amazon Basin exchange sediments to deliver nutrients to wetlands, the researchers explained. This sustains biodiversity and food supplies across the continent. As many of the planned dams are located far upstream, they could cause enormous disruption to the flow of sediments downstream.

“If all the planned dams in the basin are constructed, their cumulative effect will trigger a change in sediment flowing into the Atlantic Ocean that may hinder the regional climate,” said Professor Edgardo Latrubesse, a geologist at the University of Texas.

The team found that damage could spread all the way from the eastern slopes of the Andes to the Atlantic Ocean.

The watershed of the largest tributary to the Amazon, the Madeira River, was most vulnerable to the impacts of damming, with an index of above 80. The river is home to the most diverse fish population in the Amazon, but the construction of two large dams on the river has caused its sediment concentration to fall.

“Citizens of the Amazon Basin coutries will ultimately have to decide whether hydropower generation is worth the price of causing profound damage to the most diverse and productive river system in the world,” the researchers conclude in Nature.

“If those decisions are made within the context of a comprehensive understanding of the fluvial system as a whole, the many benefits the rivers provide to humans and the environment could be retained.”

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