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Implications of dam obstruction for global freshwater fish diversity
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
2012 (English)In: BioScience, ISSN 0006-3568, E-ISSN 1525-3244, Vol. 62, no 6, 539-548 p.Article in journal (Refereed) Published
Abstract [en]

Dams are obstructing rivers worldwide, impairing habitat and migration opportunities for many freshwater fish species; however, global data linking dam and fish distributions have been limited. Here, we quantify dam obstruction at the biogeographic scale of freshwater ecoregion, which provides the spatial framework necessary to assess the risk of fish species loss due to dams and allows us to identify both ecoregions and genera at risk. Nearly 50% of the 397 assessed freshwater ecoregions are obstructed by large- and medium-size dams, and approximately 27% face additional downstream obstruction. A synthesis of obstruction data and fish traits indicates that taxa such as lampreys (Lampetra spp.), eels (Anguilla spp.), and shads (Alosa spp.) are at particular risk of species loss. Threatened ecoregions with heavy dam obstruction and above-average counts of total, diadromous, or endemic species are found on all continents and include the Murray-Darling Province, Southern Italy, the Lower and Middle Indus Basin, West Korea, the South Atlantic region of the United States, the Upper Parana, and Mobile Bay ecoregions.

Place, publisher, year, edition, pages
2012. Vol. 62, no 6, 539-548 p.
National Category
Zoology Environmental Sciences
URN: urn:nbn:se:umu:diva-2644DOI: 10.1525/bio.2012.62.6.5ISI: 000305262500005OAI: diva2:140869

Manuscript version included in dissertation with title "Dam obstruction among the world's freshwater ecoregions and implications for global freshwater fish diversity"

Available from: 2007-10-18 Created: 2007-10-18 Last updated: 2013-10-03Bibliographically approved
In thesis
1. Ecohydrologic impacts of dams: A global assessment
Open this publication in new window or tab >>Ecohydrologic impacts of dams: A global assessment
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This dissertation aims to improve our understanding of how dams and reservoirs impact freshwater systems worldwide. The following questions were addressed specifically: 1) what are the spatial patterns and magnitudes of flow regulation and channel fragmentation by dams globally; 2) how are dam impacts distributed biogeographically, and which are the biogeographic regions and taxa most threatened by dam impacts; and 3) how can climate change and dams be expected to interact in basins, and what management actions would mitigate adverse interactions? Results show that the majority of the world’s large river systems are fragmented and have their flow altered by dams. Exceptions to this tend to lie in regions inhospitable to hydropower development, such as northern tundra, or in the least economically active regions. The biogeographic distribution of dam impact is widespread, both at terrestrial and freshwater scales, representing significant threat to global biodiversity. Relatively species-poor tundra is the world’s only terrestrial ecoregion which remains predominantly unaffected by dams. Nearly half of the world’s freshwater ecoregions are internally fragmented by dams, and ecoregional distinctions may be artifically imposed by dams in many cases. Freshwater ecoregions with the highest counts of total and endemic species remain relatively unobstructed, representing significant conservation potential. Diadromy is one of the few fish traits indicative of vulnerability to dams for which data are sufficient for global scale analysis. Lampreys (Lampetra spp.), Eels (Anguilla spp.) and Shad (Alosa spp.) are examples of genera particularly vulnerable to dams because their distributions coincide with the most heavily fragmented freshwater ecoregions, and a large proportion of the coincident species for each genera are diadromous. Due to changes in discharge and water stress, the area of large river basins in need of management interventions to protect ecosystems or people will be much greater for basins impacted by dams than for basins with free-flowing rivers. Proactive measures that restore the natural capacity of rivers to buffer climate-change impacts are more desirable than reactive actions since they may also lead to environmental benefits such as higher water quality and restored fish populations – benefits which may later be unattainable.

Place, publisher, year, edition, pages
Umeå: Ekologi, miljö och geovetenskap, 2007. 17 p.
dam; reservoir; river regulation; flow alteration; fragmentation; freshwater biodiversity
National Category
Oceanography, Hydrology, Water Resources
urn:nbn:se:umu:diva-1394 (URN)978-91-7264-429-8 (ISBN)
Public defence
2007-11-09, 5, Uminova Science Park, Tvistevägen 48, Umeå, 10:00 (English)
Available from: 2007-10-18 Created: 2007-10-18 Last updated: 2012-07-09Bibliographically approved

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Reidy Liermann, CatherineNilsson, Christer
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