Environmental Engineering Reference
In-Depth Information
higher than for larger patches. Furthermore, organisms that can only survive
in the habitats provided in large patches would become locally extinct. If we
are to maintain species and minimise maintenance costs, it would be expedi-
ent to design a landscape with an optimum number of small, medium and
large patches.
In landscapes where clearing has reduced native vegetation cover to less
than 30 per cent, the emphasis is on revegetation. For revegetation to be effi-
cient and effective, we need to refine our understanding of the different
landscape design elements. At present, revegetation involves planting or
direct seeding, which is both labour intensive and expensive.
Much research is needed in areas such as:
•
where in the landscape should vegetation be placed?
•
how should the condition of current vegetation be improved?
•
what sort of species and structural complexity is necessary?
•
how can regeneration of remnant vegetation be used to enhance
revegetation?
These important questions must be resolved if we are to address environ-
mental problems in the landscape.
Landscape design for hydrology and ecosystem function
Revegetation programs have multiple objectives and must therefore be
designed for restoring ecosystem function, including hydrology, mainte-
nance of habitat and movement of biota.
Clearing or intensification of land use usually occurs in places with the
most productive soils. Native species are lost as habitat is lost or degraded.
The outcome for fauna and flora will depend on which habitats are cleared
and how different species use the landscape. The effect on species of lost
connections between patches on native vegetation will depend on their life
history, characteristics and mobility.
Management options for controlling salt delivery to land and water
include reversing its delivery by reintroducing perennial deep-rooted trees
and shrubs. This will greatly reduce the amounts of water moving beyond
the root zone and return recharge rates to levels similar to those under native
vegetation before it was cleared to make way for annual crops and pastures.
Successfully managing the cause of salinity depends on reducing groundwa-
ter recharge.
