A major hydroelectric dam in the Amazon basin has severely reduced biodiversity.

Credit: Eduardo M. Venticinque

Brazil's Balbina Dam left more than 3,000 square kilometres of Amazonian forest underwater and created thousands of islands (pictured) when it was built in 1986. Maíra Benchimol and Carlos Peres from the University of East Anglia in Norwich, UK, surveyed 37 of these islands for 35 large and medium-sized mammal, bird and reptile species, using walking surveys and motion-activated cameras.

They estimate that, in the 26 years between the dam's construction and their survey, isolation has led to an overall species loss of 70% across all islands created by the dam, with smaller islands suffering the most. Just 25 of the 3,546 islands are likely to host 80% or more of the animals that they looked for. Such negative impacts have not been generally considered, and biodiversity impacts should be better assessed before future hydropower projects go ahead, the authors suggest.

PLoS ONE http://doi.org/5xh (2015)