Indian Himalayan basins are earmarked for widespread dam building. However, the aggregate effects of these dams on the ecosystems are unknown.
Maharaj K. Pandit & R. Edward Grumbine investigate the impact of the ongoing and proposed dam construction in the Himalayan basins of India based on spatial analyses, geographic distribution of dams, species loss and land-cover change. We highlight the most important findings from their paper in Conservation Biology, 2012.
- These findings are the first indication of the dire effects of proposed dam building in the Indian Himalaya on terrestrial ecosystems and their biological diversity. For the purposes of estimating dam-densities the authors considered projects under construction and proposed projects. If all proposed 292 dams are constructed, the region will have the highest density of dams in the world.
- The projected forest loss from submergence and dam-building activities causing land-cover change is likely to prove detrimental to the survival of species.
Three major Himalayan river basins in India were studied by the authors – Ganga, 1,086,000 km; Indus, 930,000 km, Brahmaputra, 580,000 km. Dams are being planned in these basins due to their hydropower potential based on the significantly high annual water discharge.
Locations (elevation), and installed capacities (MW) of 292 of the proposed dams were considered. Size, height, water-storage and run-of-the-river design, and details of dam-building activities in forested or non-forested areas were some of the parameters available for 32 of the dams.
- Spatial Analyses was employed using the ArcGIS software (Mapping & analysis) to help determine the extent of deforestation due to dam building.
- Geographic Distribution of Dams was closely tracked to project dam density, extent of land-cover change and loss driven by dam building activities such as infrastructure building, mining, muck dumping, and tunneling, which can have effects similar to that of submergence. Conversion of forests for dam building is equalled to loss of land cover due to intense human use and loss of natural values. From the data on the 32 dams, the average forest area used per megawatt hydroelectricity generated was calculated to project forest lost due to submergence.
- To estimate potential effects of dams on species (angiosperms, mammals, birds, fishes, and butterflies), Pearson’s correlation coefficient was applied to test the strength and significance of the correlation between the number of dams and species richness.
- A Species–Area Relation (SAR) model was applied to ascertain the extent of species loss driven by deforestation due to dam-building activities alone. Short-term projections of species extinctions were made up to 2025 and long-term projections were made up to 2100.
- There were 109 proposed dams in the Brahmaputra, 89 in the Ganga, and 94 in the Indus River basins. The Ganga basin would have the highest number of dams (1/18 km of river channel dammed), followed by the Brahmaputra (1/35 km) and the Indus (1/36 km). Temperate regions would have the highest number of dams (52%), followed by tropical and subtropical (36%) and alpine regions (12%).
- At current deforestation rates combined with loss of forest cover due to dam-related activities, total forest cover in the Indian Himalaya in 2025 is estimated to reduce by 0.32% if dams are built only in already-degraded forests, and 0.73% if dams are built haphazardly across the landscape including dense forests.
- There is a clear overlap between areas with maximum numbers of dams and species in the Indian Himalaya. Over the next 13 years, dam-building activity alone, if carried out in already-degraded forests, was predicted to lead to the extinction of 10 angiosperm and 3 vertebrate species, and haphazard dam building would result in species extinctions doubling over the same period. By 2100 extinction projections indicated a potential loss of 1505 angiosperms and 274 vertebrates driven by background deforestation and dam building combined.
- Disturbed forests had 35% lower tree species richness, 42% lower tree density, and 30% lower tree basal cover compared with undisturbed forests.
Due to lack of focus on the ecological evaluation of large-scale development, the economic & social benefits of dams seem to outweigh the grave issue of species losses. This is further compounded by the fact that the GOI has not explored any other alternatives beyond hydropower to meet the country’s future energy requirements. The findings of this study should aid in improved assessment of hydropower development in the Indian Himalaya and also equip civil groups with an ecological argument in their movements against dams.
CI volunteer Urvashi Bachani helped summarise this article for Conservation India. The original paper titled ‘Potential Effects of Ongoing and Proposed Hydropower Development on Terrestrial Biological Diversity in the Indian Himalaya’ by Maharaj K. Pandit and R. Edward Grumbine appeared in Conservation Biology (Sept 2012).