Are We Destroying Our Insurance Policy? The Effects of Alien Invasion and Subsequent Restoration - Landscape Ecology for Sustainable Environment and Culture - page 346

Fig. 16.19 Snapshots capturing the change in agriculture and invasion of Black Wattle in the
vicinity of the Churchill Dam from 1954 to 2007. The Kromme River is an important water
source for the nearby city of Port Elizabeth. Important land-use changes include: dams, Black

Wattle, palmiet wetlands, dryland agriculture, and fynbos

McGuinness and Harrold 1971 ; Bosch and Hewlett 1982 ; Rowntree 1991 ; Smith
and Scott 1992 ; Dye 1996 ; Scott and Lesch 1997 ; Scott 1999 ; Le Maitre and
Görgens 2001 ; Le Maitre et al. 2002 ; Andreassian 2004 ; Dye and Jarmain 2004 ;
Scott et al. 2004 ; Calder 2005 ; Grenfell et al. 2005 ).
Land-use change over large areas has been shown to alter erosion intensity,
causing channel lengthening and a decrease in active channel width (Michalková
et al. 2011 ). In South Africa and Australia, IAP have been found to impact the
geomorphology of rivers systems by modifying the river channel, while sub-
sequent removal can lead to significant channel instability and mobilization of
sediment (Beyers 1991 ; Rowntree 1991 ; Richardson et al. 1997 ; Bunn et al. 1998 ).
With the destruction of wetlands in the Kromme, the river appears to have become
more braided and sinuous with time. It is difficult to be certain about channel