New research by the University of Stirling has found that hydroelectric reservoirs are directly linked to sustained species extinctions on islands. Reservoir islands around the world that have been created by large dams are not able to maintain animal and plant life after flooding occurs.

While these areas are often considered conservation sanctuaries that protect species from things such as hunting and deforestation, islands experience dramatic death of species following new dam constructions. This pattern is generally known as “extinction debt”. This environmental impact is currently not discussed in assessment procedures for proposed new dams.

Isabel Jones, lead author of the study, that was published in the Biological Conservation journal, says the team has found devastating reductions in species within the majority of reservoir islands that were observed. Islands have an average of about 35 percent fewer species than mainland locations nearby. The most harmed location was in South America, where the bird community suffered a massive 87 percent species loss on reservoir islands.

Jones states that researchers have been previously aware that flooding reservoirs caused instantaneous habitat and species loss, but now it has been discovered that there is a significant biological cost in the future, when the extinction debt is paid. It does not matter where the dam is located, its size or what types of species are present: there remains a sustained loss in species, with many facing complete extinction.

Conservation experts have taken a closer look at research related to species changes among birds, mammals, amphibians, reptiles, invertebrates and plants on over 200 islands that have been built by large dams. The loss of species was observed over a period ranging from less than a year to 90 years from when islands were formed due to reservoir filling.

Researchers believe more needs to be done to save these species before it is too late. There are currently over 50,000 large dams in operation around the globe, and many dams in the process of being created to help combat ever-rising energy requirements.

Co-author, Professor Carlos Peres recognizes there are practices currently in place that are meant to minimize harmful effects of major hydroelectric dams but he says this is not enough. Peres believes strong environmental licensing needs to be put into place in order to properly track loss of species. Comparing these numbers to the hydropower output may be able to help balance out the biodiversity as new infrastructure developments become reality.