Many might look at the vast volumes of water flowing through the world's largest wetland system and think that it represents a vast untapped energy source.But the dam building boom currently spreading right across the Amazon basin may be having serious and far-reaching impacts, and could even cause entire species to die out.

There are currently plans in the pipeline to build 428 hydroelectric dams in the Amazon, with a further 140 already operational or being built.On the surface, it seems like an ideal way to produce low-carbon energy, but in reality, it is not so simple.While ecological surveys are carried out before each individual dam is constructed, there is no one looking at the overall impact that all the projects will have on the wider ecosystem, and this could be a serious problem.

"The river and its individual pieces cannot be separated out," explained Victoria Baker, co-author of a new study in Nature looking into these impacts. "That an individual dam assessment can be separated from the rest of the system isn't scientifically valid."

The researchers found that there are many wide-reaching effects that are caused by each individual dam, and when looked at as a whole, reveal a worrying situation in which the integrity and persistence of entire ecosystems – and the species that live within them – are thrown into doubt.

The researchers looked at the large-scale impact that all the dams together have on the flow of the rivers, including the land use changes, erosion, runoff, and the altering of sedimentation.This last effect is thought to be the most damaging, as the flow of sediment through and across the Amazon rainforest, its rivers, and the wetlands, is a vital factor in the health and biodiversity of the basin.

As many of the proposed dams are situated upstream and in the foothills of the Andes, their impact on sedimentation will potentially be massive.Many of the ecosystems downstream rely on the movement of this sediment through the system.For example, the largest mangrove system in South America, found along the coast of Brazil and at the mouth of the Amazon, is entirely dependent on the flow of silt from the Andes to the Atlantic.

With so many species within the Amazon rainforest endemic to single regions and even individual rivers, altering these environments could have disastrous results.The researchers warn that it could well lead to the extinction of hundreds, if not thousands, of species from right across the region, and that better management and assessment of hydroelectric construction needs to be taken into account.

Source: lubas / Wikimedia Commons