Tu w kontekście ekologicznym:
"Beside interrupted passability for sediment and fish, the hard construction caused several deficits such as a straightened river course without bed sediments, lacking variability in width and depth as well as missing riparian vegetation."
http://www.ecrr.org/conf08/pdf/proceed14.pdf

"One of the four key objectives of the Bavarian Biodiversity Strategy is to make migration barriers
such as roads or dams and weirs passable from an ecological viewpoint."
http://www.cipra.org/pdfs/341_en/at_download/file

"The ice-free iorridor opened physically in early deglaciation, after 14 ka BP, but at first was not necessarily passable in an ecological sense."
http://tinyurl.com/ylcja94

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Note added at 13 mins (2009-11-22 22:15:55 GMT)
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http://tinyurl.com/ycfvdv5