Rehabilitation and Restoration Of Degraded Forests (PDF) - IUCN

Chapter 6: Approaches at the site level
in mine development and design; often they can then be dealt with by
burying the materials at depth beneath other mine tailings or overburden.
The cost of doing this may be low if the problem is recognised in
the design phase of the mine’s development but very high once a mine
has commenced operations. Conditions limiting plant growth, such as
low levels of topsoil fertility or poor soil physical conditions, also need
to be identified and dealt with by fertilisers, ripping etc. Once mining
is complete it is necessary to reconfigure the topography of the site to
minimize wind or water erosion and re-establish drainage lines.
Revegetation after mining can be done by planting seedlings or by
direct seeding, as described earlier.
Reference: Bradshaw and Chadwick (1980); Mulligan (1996) and Case Studies
8.4 and 8.5.
6.3. Directing ecological successions
What all these approaches have in common is that successions are
initiated or accelerated without any clear knowledge of the direction
they may take (Luken 1990, Weiher and Keddy 1999). It is assumed
that other plant species will colonise the sites over time from nearby
forest remnants. It is also assumed that animals will be able to migrate
to and reoccupy these new communities once appropriate habitats are
formed. In fact, however, the large number of uncertainties make it
difficult to predict outcomes.
6.3.1 The “founder effect”
This term refers to the extent to which the initial populations —
which species, how many species, density and genetic variability —
affect successional development. Will small differences in one of these
factors or in the life histories of the species chosen make large differences
in the rate of successional development? And what difference
might an exotic species rather than an indigenous species make? The
evidence to date on the consequence of using exotic species rather than
indigenous species is equivocal, although it is apparent that in some
extreme cases only exotic species will tolerate the degraded site environment.
It is also clear that the relative proportions of the species in
the initial community are very important. An example is the restoration
of land after mining at Stradbroke Island in Australia (Figure 4a).
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