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1600
Lasiocephala basalis
Lv. 1
Lasiocephala basalis
Lv. 2
1400
Lasiocephala basalis
Lv. 3
Lasiocephala basalis
Lv. 4
Lasiocephala basalis
Lv. 5
Lasiocephala basalis
Pu.
1200
1000
800
600
400
200
0
Reference site
Degraded site
Figure 4.5
The occurrence of the life stages (Lv 1-5 = larval stages 1-5, Pu = pupal
stage) of the trichopteran
Lasiocephala basalis
in a reference and a degraded site of the
river Waldaist, Austria.
The effects of climate change on stream and river
restoration success
After a long period of modification of streams and rivers, as well as their
catchments, to the needs of agriculture, industry and households, there has been
an increasing awareness of the large negative impact of these alterations. In the
Netherlands, only about 4% of the streams still have a natural morphology and
a (more or less) natural hydrology. In Denmark, only 2% are more or less natural
(Brookes 1987), and in Germany, this is 2%-5%. Environmental awareness and
concern for the loss of stream and floodplain habitats and associated biodiversity
have stimulated a major programme of stream rehabilitation and restoration,
especially physical stream restoration in Europe. For example, in the Netherlands,
70 projects were carried out in 1991, 170 in 1993 and over 200 in 1998 with a
total cost by 2006 estimated at 1.3 billion euro (Verdonschot & Nijboer 2002).
There are many ways of physically restoring streams such as reforestation of
the floodplain, re-meandering and the removal of dams and bank structures.
Newer approaches include the addition of coarse woody debris (Gippel &
Stewardson 1996; Gerhard & Reich 2000), the removal of sediment deposits in
floodplains (cf. Kern 1994) and various methods to combat the deep cutting of
streams.
For effective stream restoration, the complex links among physical parameters,
habitat diversity and biodiversity need to be understood. When a stream has been
physically restored, success, measured mainly by an increase in biodiversity,
depends on the extent of re-colonization by the original (indicator) species. This
is the 'field of dreams' hypothesis, which states 'if we build it, they will come'.
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