Environmental Engineering Reference
In-Depth Information
Fig. 16.3 An aerial photograph taken from a helicopter of Black Wattle (Acacia mearnsii) invading
the Kromme River System, South Africa. A large expanse of the river has been cleared (foreground
and right) but re-growth with the next flood or fire is inevitable due to accumulated seed-banks
Restoration has had a highly successful return on investment worldwide as it
has repeatedly been shown to improve the delivery of many ecosystem services
(Aronson et al.
2007
) and increase biodiversity (Aronson et al.
2007
; Blignaut and
Aronson
2008
). In the 1990s South Africa recognized the threat to ecosystems and
the economy by alien plants and have acknowledged the impact of alien invasion
and poor management (van Wilgen et al.
1998
). In 1996 a restoration programme
called Working for Water commenced the clearing of invasive alien plants. It has
been found to be economically viable and competitive to restore natural capital
and infrastructure rather than using expensive, traditional engineering techniques
(van Wilgen et al.
1998
,
2008
). The Kromme River Catchment, a Mediterranean-
type climate catchment in the Eastern Cape of South Africa, was selected as a
priority location for Working for Water, because of its importance in water pro-
vision for the Nelson Mandela Bay metropolitan hub. The water use of this
metropolitan hub is predicted to increase from of 100 million m
3
per annum in
2007 to about 130 million m
3
per annum by 2017 (Murray et al.
2008
). A major
aim of the Working for Water project is to make more water available by removing
invasive alien plants with high water consumption rates (McConnachie et al.
2012
). However Working for Water's ability to cope with the scale of the problem
and its efficiency over the past 15 years have been called into question (van
Wilgen et al.
1998
,
2012
; Hobbs
2004
; McConnachie et al.
2012
) (Fig.
16.4
).
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