View - ResearchGate

260
B. Baur and S. Schmidlin
(Grand Canal d’Alsace). During channelisation, flood control dams were
built, stone groynes were constructed to strengthen the channel, and some
parts of the river bank were reinforced by stones.
Since Roman times, the Rhine has been a navigable waterway, carrying
travellers and goods deep inland. As the river became more important as
transport route, it was channelled even more to increase its discharge and
maintain its depth. In modern times, cargo shipping on the Rhine is possible
from Rotterdam (North Sea) to Rheinfelden, 20 km upstream of Basel. The
importance of international shipping increased further with the construction
of river-connecting canals. The Rhine-Main-Danube Canal connects the
Rhine via the Danube with the Black Sea which, in turn, is connected by canals
and rivers to the Caspian Sea (see Chap. 5). Another navigation route to the
Black Sea and Caspian Sea is the German Mittelland-Elbe-Vistula-Pripyat-
Bug-Dnieper canal system.
Parallel to the channelisation, the floodplain of the Rhine has been extensively
modified to extend agricultural and industrial areas and settlements.
Nowadays, the Rhine is a completely man-manipulated river, more intensively
used than ever before (Tittizer and Krebs 1996). Besides its function as transportation
route, it provides water for communities and industry, is used to
generate hydroelectric power, provides cooling water and a means of effluent
transport, and is increasingly a focus for recreation. Despite profound alterations
of river characteristics, the river still has a large (albeit not unlimited)
self-cleaning capacity, and natural and semi-natural banks and areas of the
floodplain, with abandoned meanders, brooks, sand and gravel pits, and remnants
of riparian forest still harbour an extraordinarily high diversity of
plants and animals, and are therefore of high conservation value (e.g. LfU
2000; Baur et al. 2002).
15.3 Native Biodiversity and Invasion History
Faunal diversity decreased dramatically in the river Rhine between 1900 and
1970 (Kinzelbach 1972; Van den Brink et al. 1990; Streit 1992). For example,
species richness of selected groups of macroinvertebrates in the Dutch section
of the Rhine declined from 83 species in 1900 to 43 species in 1940 and to
41 species in 1981/1987 (Van den Brink et al. 1990; Den Hartog et al. 1992).
Omitting the non-native species arriving in the 20th century, however, the
total number of species for 1940 would be 40, and only 27 for 1981/1987. Schöll
(2002) presented a list of 21 typical riverine macroinvertebrate species (seven
mayflies, 10 stoneflies and four caddis flies) occurring in the German part of
the Rhine in 1900 – none were found in the river between 1960 and 2000. Most
probably, these specialized benthic species went extinct in the river Rhine.
However, the actual causes of extinction are unknown. In the Rhine near