Rehabilitation and Restoration Of Degraded Forests (PDF) - IUCN

Box 4. Is ecological restoration ever possible?
Chapter 4: Why undertake forest landscape restoration?
Restoration, as defined in Box 3, is a difficult undertaking, both
in principle and in practice. There is some question as to whether
it is even possible. The definition of restoration implies that the
identity and population sizes of the plants and animals once
present at a particular site are known. This is rarely the case. In
many situations the best that can be done is to infer the nature of
the original ecosystem from previous descriptions or remnants of
communities. The definition also implies that these communities
were static and would have remained unchanged over time. But
this, too, is unlikely to be the case. Many communities undergo
successional change, often over a period of time involving
hundreds of years. Even mature ecosystems commonly exist in a
state of dynamic equilibrium; changes occur in their composition,
even in the absence of degradation. These difficulties mean that
restoration can be both an uncertain goal and a shifting target.
Restoration can also be difficult for other reasons. Our knowledge
of ecological processes is imperfect and our capacity to predict, let
alone direct, ecological successions is limited. In many cases
chance events such as weather or the timing of flowering or
seeding have a major effect on the way successions develop. This
means it might be difficult to achieve a particular outcome even if
the target could be ascertained. Further, the large numbers of
plant and animal species present in many communities mean that
the ecology of species is poorly known. This makes it difficult to
assist or encourage them to re-enter a degraded site.
The target might also become unattainable because some of the
original species have become extinct. Exotic species may have
become naturalised after a long period of human intervention.
Such is likely to be the case, for example, with the ecosystems of
Europe and the Mediterranean basin or in China. In these cases
simply fostering species-rich communities might be a more
appropriate goal. In other situations the extent of topsoil loss, site
exposure or salinity levels may be so great that restoration would
be too expensive even if the technical means were available.
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