Climate Change and the Hydrology and Morphology of Freshwater Ecosystems - Climate Change Impacts on Freshwater Ecosystems - page 66

but to increase in almost all parts of northern and north-eastern Europe. Changes
in seasonality are also expected, with most climate models showing a general
precipitation decrease in summer months and an increase in autumn and winter
months. Furthermore, extreme daily (especially summer storm) precipitation
events may become more frequent (Räisänen et al . 2003), discharge may vary
more, with more extremes (higher spates and longer droughts), and annual
discharge regime may become less predictable (Arnell 1999).
A key concern is how this will influence the morphology, hydrology, habitats
and species diversity in rivers and lakes. In large parts of Europe, channel
straightening, weir and dam construction, disconnection of the river from its
flood plain and alteration of riparian vegetation have already severely reduced
the ecological quality of streams and rivers (Kristensen & Hansen 1994; Armitage &
Pardo 1995; Hansen et al . 1998). In lakes, water-level fluctuations affect littoral
habitats through changes in light, sediment and wave regimes (Wantzen et al .
2008), and the modification of shorelines affects macrophytes (Radomski &
Goeman 2001; Elias & Meyer 2003), macroinvertebrate communities, littoral
fish communities and overall biodiversity (Jennings et al . 2003; Scheuerell &
Schindler 2004).
Predicted changes in land use
Land-use change
Stream hydrology is also influenced by changes in land use (e.g. Poff et al .
1997) through (i) changes in infiltration, evaporation, run-off and discharge
regime (Knox 1987); (ii) changes in riparian vegetation and channel morphology;
and (iii) changes in the input of sediment (Reid & Page 2003; Wissmar & Craig
2004), organic matter (Allan et al . 1997), nutrients, pesticides and other
pollutants. Most studies concerned with the influence of land-use change on
rivers have been conducted at a large spatial (e.g. Feld 2004; Townsend et al .
2004), but local land-use change is also important, for example, through the
removal of riparian vegetation, which may increase erosion and sediment
inwash. In addition, land use can intensify or buffer the effects of climate
change. If, for example, land is drained, an increase in precipitation will result
in a greater run-off and, consequently, more peak hydrographs. In contrast,
forests can retain rainwater and reduce the impact of increased precipitation on
run-off.
European land use is expected to change significantly over coming decades
(Busch 2006) with the amount of agricultural land decreasing and the amount of
forest and urban land increasing (Schröter et al . 2005; Verburg et al . 2008),
though the loss of agricultural land elsewhere, the rising world population and its
need to be fed and a demand for biofuels may reverse these expectations. Such
land-use changes have had and will continue to have a strong influence on stream
and river hydrology and morphology (Sandin 2009). A rare example of a site
with a long-term record of changes in river morphology embraces the tributaries
of the River Vecht in the Netherlands. From the end of the 19th century until the