THEGIFT777 / Getty imagesDam in South Africa, one of the regions with a drastic reduction in the areas that fish can liveTHEGIFT777 / Getty images
Habitat fragmentation has dramatic effects not only on land animals, but also on aquatic ones. Experts from the Environmental Assessment Agency, Leiden University, and Radboud University, all in the Netherlands, and Leipzig University, Germany, assessed the impact that 31,780 hydroelectric dams around the world have had on the geographic range of 7,369 species of freshwater fish. More than half of the species have lost part of their habitat. Seventy-four fish species in Brazil, China, India, the USA, South Africa, and the East Adriatic Coast lost more than 50% of the geographic area in which they live, including 18 species under threat of extinction. When considering both small and large dams, the total impact is two to four times greater than the effects of only large dams with a height of at least 15 meters (m). In Brazil, especially in the Amazon, Tocantins, and Paraná river basins, the addition of small dams to the analysis increased habitat loss from 3.7% to 8.3%, reducing the area where fish live by up to 4,232 square kilometers (km2). According to the study, the addition of small dams reveals the potential extinction of six species, including three catfish (Glanidium catharinensis, Hypostomus kuarup and Hemiancistrus megalopteryx), the Torres toothcarp (Cnesterodon omorgmatos), a killfish (Melanorivulus pinima), and a darter (Characidium satoi), with a total range area of up to 1,500 km2 (Global Change Biology, February 1).
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