Rampant dam-building across Amazonia causes severe impacts on wildlife, as shown by a paper just published in the scientific journal Biodiversity and Conservation by an international team of researchers lead by BiOME Consulting associate Dr Alexander Lees of the Cornell Lab of Ornithology, USA. The watersheds of the Amazon River and adjacent Tocantins River are a very attractive prospect to dam builders as these basins account for 6% of total global hydropower potential. The nine countries that share the Amazonian biome have already built 191 dams across the basin and are planning to develop 243 additional dams. The majority of these are concentrated in the southern Brazilian Amazon. These southern Amazonian dams include the gigantic Belo Monte dam on the Xingu River, which will have a 11,233-Megawatt installed capacity when completed in 2019. Belo Monte has rarely been outside of the news given its impacts on both indigenous communities and regional biodiversity. Coupled with its huge cost overruns, it has become a cause célèbre in debates surrounding infrastructure development in Amazonia. Expansion of the hydropower network is not only aimed at ensuring national energy security, it also facilitates expansion of regional mining operations for bauxite, nickel, copper and gold by providing taxpayer subsidised electricity for these industries.

Dam projects are not distributed evenly across Amazonia because building a dam requires a stretch of river that includes a marked gradient in altitude, which typically means rivers with rapids.

This means that Amazonian dams are concentrated on the ancient weathered ‘shieldlands’, particularly the Brazilian Shield in southern Amazonia. The nutrient-poor rivers that run across these tropical forest landscapes are home to many endemic species – species that are found nowhere else. Some of them are restricted to isolated sections of rapids only a few tens of kilometres in length. Expansion of the dam network will result in huge changes to these Amazonian rivers by obstructing movement of aquatic fauna both upstream and downstream, by submerging these rapids under huge lakes, by flooding adjacent forests and by creating forest islands that cannot sustain viable animal and plant populations. These changes to the habitat will also be followed by indirect effects on the region’s fauna and flora because the influx of people and money are expected to result in higher deforestation rates in the areas affected by dams.

Dead flooded forest caused by the Balbina Dam (copright Alexander Lees)

Dead flooded forest caused by the Balbina Dam (copright Alexander Lees)

According to Dr Lees, the current dam-building regime will forever change the process of human disturbance in lowland Amazonia and will likely result in myriad species extinctions in what is probably the most biodiverse freshwater ecosystem on the planet. According to Dr Lees “The change from fast-flowing to still waters after river impoundment likely favours generalist or invasive species over the specialist and often micro-endemic species that require fast-flowing rivers and exposed rocky islets”.Priority attention’ is being directed towards a suite of fish species that occupy these rapids but even if they are bred in captivity these species may no longer have anywhere appropriate to be reintroduced to afterwards. River island species are also at risk from inundation – especially along the River Madeira for example which holds a suite of restricted range bird species.

“The change from fast-flowing to still waters after river impoundment likely favours generalist or invasive species over the specialist and often micro-endemic species that require fast-flowing rivers and exposed rocky islets”

This loss, degradation and fragmentation of riparian habitats will eventually lead to a large loss of regional biodiversity and lead to a simplification of the community of species. Dr Jansen Zuanon of Brazil’s National Institute for Research in Amazonia (INPA) in Manaus highlighted that the diversity of freshwater wildlife in Amazonia is still poorly known – 30% to 40% of the freshwater fish species have still not yet been formally named.

Professor Carlos Peres of the University of East Anglia says that “Even terrestrial wildlife and woody plants in forest areas well above the water-level of hydroelectric reservoirs are not safe, as these populations typically become stranded in artificial archipelagos whose biodiversity is committed to extinctions and rapidly eroded over time through the ravages of habitat isolation and edge effects”.

Dr Philip Fearnside of INPA emphasizes that “the planned dams are not an inevitable part of Brazil’s future development because they are not necessary. Brazil has many better options, including investing in energy efficiency, ceasing to export electricity in the form of aluminium and other electro-intensive commodities, and tapping the country’s vast potential wind and solar resources. The severe impacts of Amazonian dams make pursuing other options very much in Brazil’s best interest”.

The Xingu river

The Xingu river

Although many of the species threatened by dams in Amazonian Brazil are strictly protected by Brazilian law from being hunted or traded, there are legal provisions that would allow them to be extirpated by these Amazonian dam-building projects. According to Dr Maurício Schneider of the Chamber of Deputies – the lower house of the National Congress of Brazil — “This lack of legal protection for Amazonian wildlife threatened with global extinction is in stark contrast to the situation in the Brazilian Atlantic Forest, where a law confers protection on threatened species if intervention would jeopardize their survival”. Dr Schneider added that a bill (3486/1989) proposing similar protection for the Amazonian biome was rejected in the lower house and that these measures should be reconsidered.

A major challenge for conservationists is to understand the cumulative impacts of Amazonian dam developments and indeed the impacts of any large-scale campaign of infrastructure improvement. Huge amounts of time and money have been spent on EIA work in Brazil associated with dam development but much of this information is hidden away from the public domain. Analysing cumulative impacts becomes ever more important as more dams are built in series and this should be accompanied by a thorough evaluation of trade-offs between biodiversity conservation, ecosystem service provision and economic development across the water-energy nexus.