Andes dams twice as numerous as thought are fragmenting the Amazon, with “huge ramifications for not only the rivers of the Andean region of the Amazon, but also for the ecology of the entire Amazon basin”

Desdemona Despair

By Claire Asher
28 February 2018

(Mongabay) – The scale of hydroelectric development in the Andean Amazon is far more extensive than previously thought, with numerous headwater dams fragmenting river habitats, disrupting natural systems, and affecting the lives and livelihoods of 30 million downstream Amazon basin inhabitants, according to a new study published in Science Advances.

If proposed dams in the region go ahead, sediment transport from the Andes to the Amazon floodplains will cease and migratory routes of freshwater fish will be blocked, threatening food security for downstream communities.

An international team of researchers led by Elizabeth Anderson, a freshwater ecologist at Florida International University in Miami, used satellite imagery to verify reported locations of existing dams in the Amazonian Andes of Columbia, Ecuador, Peru, and Bolivia, and to quantify their impact on river connectivity.

The scientists identified 142 dams currently in operation or under construction – twice the number previously estimated. This study represents “the most detailed accounting of dams in the Andean region,” says Kirk Winemiller, an aquatic ecologist at Texas A&M University, who was not involved in the study. The team also included the impact of proposed dams in their model – an additional 160 projects – and found that they would further reduce connectivity on five out of eight major Andean rivers that flow into the Amazon basin, with the Napo, Marañón, Ucayali, Beni, and Mamoré most effected.

The last large-scale survey of hydroelectric development in the Andean Amazon was published in 2012, but hydroelectric development has flourished there in intervening years, and global and regional reports often exclude small hydroelectric projects – estimated to outnumber large hydropower plants 11 to 1, according to another study published last month – meaning that other research using past published data has seriously underestimated the number and impact of dams in the region. […]

Fragmentation of the Andes headwaters has “huge ramifications for not only the rivers of the Andean region of the Amazon, but also for the ecology of the entire Amazon basin,” says Winemiller. [more]

Andes dams twice as numerous as thought are fragmenting the Amazon

By JoAnn Adkins
2 February 2018

(FIU News) – The Andean Amazon is being rapidly altered by a wave of hydropower development and the consequences have been underestimated, according to newly released research.

A team led by professor Elizabeth Anderson from the FIU Institute of Water and Environment documented 142 existing dams and 160 proposed dams for rivers draining Andean headwaters of the Amazon. The researchers are concerned the proposed dams could result in significant losses in river connectivity, threatening fish populations and forever changing river channels and floodplains.

The greater Amazon is one of the most prolific, biodiverse habitats in the world and Andean rivers have a disproportionate influence on the lowland areas. Andean rivers also predominantly define the formation of rivers downstream, controlling their curves and sediment. With as many as 5,000 species of fish inhabiting the waters, the rapid development of hydropower is a potential threat to these species that are a primary source of food and income for the 30 million people who live along the Amazon basin. If the proposed development continues, only one of the eight major Andean Amazon river systems would be left unimpeded.

There are also cultural implications for native people who live along the rivers, some of whom believe the waters are sacred.

The team collaborated with local governments and conservation organizations to compile international data on the dams, assembling the most comprehensive database of dams in the Andean-Amazon region. The result is a system-wide look at the overall impact, which presents a very different picture than when assessing impact of individual dams on individual systems.

“I hope that by showing the regional trends and that there is widespread river alteration happening, this research can lead to more coordinated development and help to highlight the importance of keeping some rivers free-flowing in the region,” Anderson said.

The research team’s efforts are already paying off. The international collaboration behind this research has led to the formation of a new initiative, Rios Vivos Andinos, which aims to facilitate more regional scientific analyses that examine the linkages between river flows, freshwater biodiversity, and human well-being. Anderson and her collaborators recently received funds from the MacArthur Foundation to support these efforts.

The research was published this week in Science Advances and is a collaboration between 15 institutions spanning eight countries. It was supported, in part, by grants from USAID, the MacArthur Foundation, and the Amazon Fish Project.

Hydropower development alters the Amazon, researchers find

ABSTRACT: Andes-to-Amazon river connectivity controls numerous natural and human systems in the greater Amazon. However, it is being rapidly altered by a wave of new hydropower development, the impacts of which have been previously underestimated. We document 142 dams existing or under construction and 160 proposed dams for rivers draining the Andean headwaters of the Amazon. Existing dams have fragmented the tributary networks of six of eight major Andean Amazon river basins. Proposed dams could result in significant losses in river connectivity in river mainstems of five of eight major systems—the Napo, Marañón, Ucayali, Beni, and Mamoré. With a newly reported 671 freshwater fish species inhabiting the Andean headwaters of the Amazon (>500 m), dams threaten previously unrecognized biodiversity, particularly among endemic and migratory species. Because Andean rivers contribute most of the sediment in the mainstem Amazon, losses in river connectivity translate to drastic alteration of river channel and floodplain geomorphology and associated ecosystem services.

Fragmentation of Andes-to-Amazon connectivity by hydropower dams