Ecosystems inevitable fate caused by dams

There is a global pattern of sustained species extinction within hydroelectric reservoirs. 

Hydropower has been pushed in the Americas, Africa and Europe by dam developers under the idea that it is an eco-friendly form of alternative energy. Nonetheless a recent study by the University of Stirling has shown there is a global pattern of sustained species extinction on islands within hydroelectric reservoirs.

Scientists discovered that the reservoir islands created by large dams don't maintain the same levels or animal nor plant life than the one found before the dam's construction. This creates what's known as an extinction debt, the incremental but inexorable loss of species and diminishment of biodiversity over time.

Besides this hydropower disrupts the flow of nutrients, interrupts marine migration routes and harms fisheries. Flooding destroy forests, increase the release of greenhouse gases and also displaces human communities, even submerging indigenous territories.

More than 75% of the cases studies show dams have had an overall negative impact on island species and affect factors like species population, ecological community composition and species behavior.

Isabel Jones lead author of the study, "Extinction debt on reservoir land-bridge islands" available in the journal Biological Conservation, said: “We found a devastating reduction in species over time in the majority of reservoir islands we studied. On average, islands have 35 per cent fewer species than nearby mainland sites, however one South American bird community suffered as much as 87 per cent loss of species on reservoir islands."

“We know flooding reservoirs causes immediate loss of habitat and species, but we now find there is also a significant future biological cost as the ‘extinction debt’ is paid." She states that no matter where the dam is locates nor the island size or species presents there is an imminent risk of taking species towards extinction.

Among more than 200 islands studied are the Balbina reservoir project in Brazil and China's Thousand Island lake. The team investigated the loss of species over a period of less than a year to over 90 years from when the islands were created.

Researchers believe more needs to be done to understand the long term consequences of dam's construction as over 50,000 large dams are operating globally, representing a high risk for biodiversity.

Study co-author Carlos Peres also said, "Current practices to minimize the detrimental impacts of major hydroelectric dams include tropical forest set-asides, but this is a mirage if the remaining terrestrial biota becomes stranded in small islands - this needs to be taken into account in new infrastructure developments. "

“Strong environmental licensing should be put in place to assess species losses versus the amount of hydropower output to even-up the biodiversity balance sheet.”


LatinAmerican Post | Maria Andrea Marquez

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