Global river systems are increasingly being altered by the construction of dams and barrages to supply water and energy. Such hydrological structures have far-reaching adverse environmental impacts, especially on wetland ecosystems. Wetland-dependent birds are particularly vulnerable to the deterioration and shrinking wetlands, and are declining as a result of this threat.
There are over 48,000 large dams worldwide supplying drinking water sources, generating hydroelectric power, irrigating land and preventing floods (WWF 2016). Whilst more construction projects are underway to meet the demands of global population growth, there has been increasing concern over the far-reaching adverse environmental impacts of such hydrological structures (Junk et al. 2013; Sun et al. 2012; WWF 2016).
Large dams and barrages fragment river basins, leading to the loss of valuable ecosystem services, the deterioration of complex ecosystems and declines in biodiversity (Hagenmaier et al. 2016). Of the 338 globally Important Bird and Biodiversity Areas (IBAs) categorised as ‘in Danger’ (IBAs under very high pressure presently and in need of immediate action – BirdLife International 2017), 15% (50) are threatened by dams and water management. Wetlands are particularly vulnerable to the presence of dams and river management activities as they are dependent on seasonal flooding to sustain ecosystem function (Junk et al. 2012; Sun et al. 2012). Almost all (48) of the IBAs threatened by damming contain areas that qualify as wetlands (BirdLife International 2017), with 58% of these encompassing or overlapping Ramsar wetlands sites. Damming reduces flooding to wetlands, causing them to shrink and become inhospitable for a range of aquatic biota, including wetland-dependent birds (Sun et al. 2012).
In China, the Three Gorges Dam has disturbed the ecological function of lake wetlands by altering the hydrological regime downstream and reducing seasonal flooding to lake wetlands (Sun et al. 2012). Consequently, decreasing wetland water levels have directly impacted a range of waterbirds dependent on these wetlands, such as the Critically Endangered Siberian Crane (Grus leucogeranus) and Vulnerable White-naped Crane (Antigone vipio) (BirdLife International 2017; Harris and Mirande 2013). In Ethiopia, the Fogera floodplains support various wetland-dependent birds including the Vulnerable Wattled Crane (Bugeranus carunculatus) and the Near Threatened Lesser Flamingo (Phoenicopterus minor) (BirdLife International 2017). Of these floodplains, the Welala and Shesher Wetlands have significantly shrunk due to the downstream effects of damming and water diversion practices on the Ribb River. As a result, the survival of these wetlands and the wildlife they sustain are threatened (Atnafu et al. 2011).
Related Case Studies in other sections
Atnafu, N., Dejen, E., and Vijverberg, J. (2011) Assessment of the ecological status and threats of Welala and Shesher wetlands, lake Tana Sub-Basin (Ethiopia). J. Water Resource Prot. 3: (7) 540-547. doi:10.4236/jwarp.2011.37064
BirdLife International (2017) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 28/03/2017
Hagenmaier, E., Mingoia, S. and Worthen, N. (2016) Impact of Dam-Reservoir Systems on Wetlands with an emphasis on John Redmond Reservoir. Accessed on March 24, 2017. http://academic.emporia.edu/aberjame/student/hagenmaier1/reservoirs.html#top
Junk, W. J., An, S., Finlayson, C. M., Gopal, B., Kvet, J., Mitchell, S. A., Mitsch, W. J. and Robarts, R. D. (2013) Current state of knowledge regarding the world’s wetlands and their future under global climate change: a synthesis. Aquatic Sci. 75: 151–67.
Sun, Z., Huang, Q., Opp, C., Hennig, T. and Marold, U. (2012) Impacts and implications of major changes caused by the Three Gorges Dam in the middle reaches of the Yangtze River, China. Water Resour. Manag. 26: 3367–3378.
World Commission on Dams (2000) Dams and development: a new framework for decision-making. London: Earthscan.
WWF. 2016. Dams – blessing and curse? Accessed March 24, 2017. http://wwf.panda.org/what_we_do/footprint/water/dams_initiative/
Compiled: 2004 Last updated: 2017
BirdLife International (2017) Large dams and barrages are an increasing threat to wetland-dependent birds. Downloaded from http://www.birdlife.org on 21/03/2018