Hydropower reservoir warnings over biodiversity costs

New moves to increase the use of  hydropower in the Amazon basin is threatening to decimate biodiversity in the region.

Scientists from the University of East Anglia (UEA) are warning current and future hydropower developments should avoid flooding forests to minimise biodiversity loss and disruptions to ecosystems in Amazonian forest islands.

The study sound deforestation, habitat loss and fragmentation are linked and are driving the ongoing biodiversity crisis, with hydropower to blame for much of this degradation. In lowland tropical forests, river damming typically floods vast low-elevation areas, while previous ridgetops often become insular forest patches.

In the study, scientists from UEA, Portugal and Brazil used network theory to understand how insular habitat fragmentation affects tropical forest biodiversity. This approach perceives habitat patches and species as connected units at the whole-landscape scale, encompassing a species-habitat network.

The authors studied 22 habitat patches, consisting of forest islands and three continuous forest sites, which were created by the Balbina Hydroelectric Reservoir, one of the largest in South America. The 608 species surveyed represented eight biological groups: mid-sized to large mammals; small non-flying mammals; understorey birds; lizards; frogs; dung beetles; orchid bees and trees.

The study revealed widespread species extinction, especially of large-bodied species, but this varied across different groups of plants, vertebrates and invertebrates. Island size determined the persistence of species diversity, with just a few islands holding the most diversity.

Large tracts of tropical forests become rarer as they are subdivided and isolated into small habitat patches. The removal of larger forest sites will exert the greatest impact, likely inducing secondary extinctions of species that occur only at a single site or those that have larger spatial requirements.

Professor Carlos Peres, co-author of the study, and professor of environmental studies at UEA said: “Tropical developing countries are still hellbent on creating vast hydropower reservoirs under the banner of ‘green’ energy.

“This is a double-jeopardy because we lose both the unique lowland biodiversity and the carbon stocks of the now inundated old-growth forests.

“Such actions also generate a powerful methane pump, never mind the huge financial costs of mega-dams compared to diffuse in-situ electrification based on low-impact renewables.

“We need a much better strategic dialogue between sustainable energy security and biodiversity conservation, particularly in the world’s most biodiverse emergent economies.”

Dr Carine Emer, a co-author of the study from the Rio de Janeiro Botanical Garden, said: “The beauty of this study lays in the combination of sophisticated network and statistical analyses, with the natural history of high-quality species inventories from an astonishing tropical living lab.

“More than 3,000 islands were created 35 years ago due to the Uatumã River damming, and by studying these we were able to understand the functioning of such a complex and rich human-modified landscape.”