Environmental Engineering Reference
In-Depth Information
Deteriorating water quality and dryland salinity are direct consequences
of loss in biodiversity. The widespread removal of native vegetation has had
a dramatic and immediate impact upon ecosystem function, causing major
changes in the hydrological cycle as well as changes in surface flow of wind
and water. The complex root systems of grasses, shrubs and trees and their
symbiotic relationship with soil fungi provide a vast network for recycling
and redirecting water and nutrients. With their removal, there may be less
buffering and more extreme run-off events. More water flows across the
landscape, moving topsoil around, eroding agricultural land and silting
watercourses. These have become severe degrading forces.
Landscape redesign: using vegetation to enhance biodiversity and
reduce land and water degradation
The sacrifice of biodiversity in agricultural landscapes has cost so much in
terms of land and water degradation that we need to rethink and redesign
our use of these landscapes in ways that maintain their integrity but still
provide for their profitable, sustainable use. Part of the solution lies in
restoring crucial elements of biodiversity to the landscape and optimising
the ecosystem services the biodiversity provides.
We noted above that a patch of native vegetation could provide many eco-
system services as well as aesthetics, shade and shelter. Both the size of a patch
isolated from other patches by large areas of agricultural land, and the
arrangement of patches on the landscape, have a profound influence on which
species survive and consequently, which ecosystem services are maintained.
The key elements of landscape design for protecting terrestrial biodiver-
sity and ecosystem functions are size, shape, separation/connectivity, species
composition, and position.
Design elements are most important for landscapes that have been
cleared to less than 70 per cent of native vegetation cover. In areas with less
than 30 per cent cover, revegetation must be designed if the return-for-
efforts are to be maximised. Where there is between 30 and 70 per cent cover,
design can help to avoid thresholds of change that cause both rapid loss of
species and change in ecosystem functions.
More research is needed into the effectiveness of conserving patches of
habitat as a way of allowing species to persist in highly cleared areas. A land-
scape strewn with small patches of native vegetation could preserve elements
of biodiversity, but the cost of maintaining these patches could be much
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