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Large dams and barrages are an increasing threat to wetland-dependent birds

Dam construction, Portugal, © Helda Costa/SPEA

In 2000, the first global survey of dams showed that their overall impact was negative leading to the loss of forests and wetland ecosystem services. In Africa, the Middle East and Europe, dams and other hydrological structures are a threat to nearly 10% of the region’s Important Bird Areas, the majority of which are Ramsar sites.


Wetlands of international importance for birds that are threatened by dams, barrages and embankments in Africa, Europe and the Middle East

Analysis of data held in BirdLife’s World Bird Database (2004).

Large dams cause major ecological changes in river basins. The first global survey of these showed that, despite some positive effects, their overall impact was distinctly negative (World Commission on Dams 2000). Large dams have led to:

  • the loss of forests and other economically and ecologically valuable habitats, the loss of biodiversity and the degradation of upstream catchment areas
  • the loss of aquatic biodiversity in upstream and downstream fisheries, and the loss of ecosystem services of downstream wetlands, such as rivers, floodplain lakes, marshes and forests, estuaries, deltas and nearby shallow marine ecosystems
  • cumulative impacts on water quality, river-flow regime and species composition, where a number of dams are sited on the same river.

A high proportion of the world’s river basins (61% of a large sample) are highly or moderately fragmented by dams (World Commission on Dams 2000). For example, in Africa, the Middle East and Europe, dams and other hydrological structures are considered to pose a threat to nearly 10% (304) of the 3,701 globally Important Bird Areas (IBAs) in this region (analysis of data held in BirdLife’s World Bird Database 2004). The great majority (87%) of the 304 potentially affected IBAs contain areas that qualify as wetlands of international importance (Ramsar Sites), according to the criteria of the Convention on Wetlands (see figure). In Asia, actual or planned dam projects are likely to have significant impacts on at least 10 globally threatened birds. Waterbirds of lowland floodplains, such as Masked Finfoot Heliopais personata and Indian Skimmer Rynchops albicollis, are affected particularly badly.



Related Species

References

World Commission on Dams (2000) Dams and development: a new framework for decision-making. London: Earthscan.

Compiled 2004

Recommended Citation:
BirdLife International (2004) Large dams and barrages are an increasing threat to wetland-dependent birds. Presented as part of the BirdLife State of the world's birds website. Available from: http://birdlife.org/datazone/sowb/casestudy/150. Checked: 24/11/2014