Small hydropower plants (SHPs) are proliferating worldwide due to incentives for sustainable energy technologies that assume small-sized dams necessarily produce low environmental impacts. However, there is mounting evidence in the literature suggesting that SHPs represent potential threats for freshwater species by modifying hydrology and reducing riverine connectivity. A major conservation challenge is that SHPs are considerably more abundant compared to Large Hydropower Plants (LHPs) – more than 80,000 SHPs currently in existence across the world (11 SHPs for every LHP in the world). Therefore, the cumulative ecological effects of SHPs in aggregate deserve urgent attention. Here, we quantify the cumulative threat of SHPs on measures of hydrologic connectivity and freshwater biodiversity, and identified the basins/sub-basins and the red-listed freshwater species that are more vulnerable to the expansion of SHPs in the country.
Results/Conclusions
The estimated impacts of SHPs and LHPs is scale dependent, with relative impacts of SHPs being more detectable at fine scales. The ratio of basins that are more impacted by SHPs ranged from 1:5 in the coarser scale of our analysis to 2:1 in the finer one. Out of the 420 red-listed freshwater species (i.e. fishes, amphibians, chelonians, crustaceans and aquatic/semi-aquatic insects), 80 species occur in basins that are more impacted by SHPs, 158 species occur in basins more impacted by LHPs, and 182 occur in basins that currently do not contain hydropower facilities. A total of 18 species are endemic of basins that have been more impacted by SHPs. Our results suggest that cumulative impacts of SHPs may be very high, and in many basins may even exceed the estimated impacts of LHPs. In addition, dozens of red-listed freshwater species occur in river basins that have been more modified by SHPs than LHPs. Although LHPs are widely recognized as causing major social and ecological impacts that require environmental impact assessments during licensing procedures, environmental policies on SHPs continue to overlook their potential for causing environmental impacts. This study reinforces the need of environmental regulations that consider the cumulative impacts of SHPs.