A view of the Furnas hydroelectric dam in the city of Sao Jose da Barra in the state of Minas Gerais in Central Brazil, January 14, 2013. (REUTERS/Paulo Whitaker)

This story has been updated.

It’s just the latest sign of mounting tension over the next stage of development in the threatened Amazon — enormous dams that will generate huge amounts of electricity, but also, inevitably, have major ecological consequences.

A report released Wednesday by Greenpeace — which is highly active in the Amazon region — has decried the Brazilian government’s plans for a huge new hydropower project in the Amazon’s Tapajós river basin, questioning both the project’s purported environmental impact and even its legality.

The organization has called for the halting of the project and urges the expansion of other clean energy forms instead. But in reality, other experts said, Brazil’s hunger for energy and major reliance on dams (rather than fossil fuels) for generating it seems unlikely to abate any time soon.

The new project, known as the São Luiz do Tapajós dam, is shooting for a maximum electricity generating capacity of more than 8,000 megawatts and, at nearly five miles wide, would block one of the last major unobstructed tributaries in the Amazon and flood thousands of square miles in the process. It’s the largest of five dams currently planned for the Tapajós river, according to Greenpeace, and one of about 200 proposed hydropower projects proposed throughout the Amazon basin.  

Hydropower is particularly favored by Brazil, where hydroelectric plants account for about 80 percent of the electricity generated in the country. But while hydropower is certainly a low carbon form of energy, scientists and activists are growing increasingly concerned about its other environmental impacts.

Recent research has suggested that damming is responsible for a myriad of detrimental effects in the Amazon basin, threatening water quality, degrading habitat for wildlife and drawing more humans into remote regions, which can indirectly drive activities like mining and deforestation. This is a major problem both for the natural environment and for the indigenous populations who live in the affected areas.

In this context, Greenpeace charges that the environmental impact assessment submitted by one of the consortia expected to bid for the project was “deeply flawed.” Representatives from Eletrobras, a state-run energy utility company and leader of the consortium that submitted the environmental impact assessment, did not immediately respond to requests for comment on the report. 

A statement from Brazil’s Ministry of Mines and Energy to The Washington Post in response to the Greenpeace report said, “The current Brazilian hydroelectric projects are characterized by the respect for the environment and the population, with previously defined plans for environmental and social compensation, improvements to the local society, and a commitment to international protocols to be followed in relation with society, as in the Equator Principles.” The statement also noted that hydropower is the cheapest energy source available in Brazil.

Even beyond the importance of scientifically sound environmental impact assessments for individual projects, though, other experts have also emphasized the need for basin-wide evaluations of the effects of damming. David McGrath, deputy director and senior scientist at the Earth Innovation Institute and a professor at the Federal University of Pará in Brazil, has previously told The Washington Post that this type of large-scale analysis should be one of the highest priorities for scientists and policymakers looking for a more complete view of how all the hydropower projects in the basin may build on one another’s impacts — although he’s also noted that the institutional capacity for such an analysis is still lacking.

While damming is widely believed to be a source of havoc in the natural environment, some experts have also pointed out that environmental destruction can feed back and negatively impact hydropower production. This is a point that was not fully conveyed in the Greenpeace paper, said Claudia Stickler, a scientist and Amazon expert with the Earth Innovation Institute, who was not involved with the report.

“The bigger deforestation problem in the Amazon as a whole is really also going to affect these hydropower projects,” Stickler said. “For me, that’s one of the most damning pieces of evidence against a lot of these big installations.”

Large-scale deforestation in the Amazon can cause trouble with water flow, Stickler explained. With fewer trees in the region to recycle water and return it to the atmosphere, rainfall patterns can actually be disrupted over time. And the landscape changes that come with deforestation can also cause more water to run off instead of soaking into the soil and being sucked up by the remaining vegetation, making the problem even worse. These factors may disrupt water flow in the Amazon’s river systems over time and lower the output of hydropower installations.

“That’s something that’s not being taken into account by the engineers that are continually doing projections of hydropower energy generation,” Stickler said.  

At the same time, the Greenpeace report argues, dams can become an indirect driver of deforestation in the region as well, by drawing workers into remote areas and leading into the construction of new roads and communities.

However, all of these complaints having been made, the solutions to the hydropower issue are still unclear. The Greenpeace report has called on the Brazilian government to halt the Tapajós project, as well as plans for other installations throughout the Amazon, and explore alternative energy sources instead. But this may be an unlikely outcome for the time being.  

“We’re talking about a giant country that really does mostly depend on hydropower production for its energy,” Stickler said. “As much as Greenpeace might not like the idea that they have economic plans that require more energy, the reality is that you’re not going to be able to do away with that.”  

In regard to alternative energy solutions, Stickler noted that Brazil’s challenges are similar to those faced in much of the rest of the world — mainly issues with efficiency and storage that, while improving, still need more independent analysis in order to evaluate how well they could take over the power that’s currently being counted on from proposed hydroelectric installations.

Even so, Stickler and other scientists have noted that the need for alternative solutions is growing greater as the devastating impacts of damming become increasingly clear. And while the São Luiz do Tapajós project will likely continue on for now, it may also become the next symbol of how profoundly human activity is changing the Amazon.