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II. Scientific Evidence Regarding Rainforest Ecology and Protection
7. PROTECTING RAINFOREST IN AN UNCERTAIN ENVIRONMENT
There are many potential sources of disturbance of rainforest
in Victoria that relate directly or indirectly to current harvesting
practices. In the absence of the necessary data, inferring the
importance of potential effects is likely to be speculative or
inferred from knowledge of other systems. Perhaps the only serious
attempt to clarify comprehensively the ecological dynamics of
the interface between rainforest and sclerophyll forest in Victoria
was made by Cameron (1992) in which he stated that Victorian rainforests
'display structural and floristic features which are clearly the
result of a history of disturbance' (p. 17). This observation
agrees with the central thesis made by Attiwill (1994 a,b) that
disturbance is a fundamental part of the dynamics of Australian
forest ecosystems, and echoes the idea expressed by Noble (1981)
that disturbance and non-equilibrial dynamics are pervasive features
of Australian ecosystems. Cameron (1992) makes implicit use of
such ideas in suggesting that the existence of rainforest at any
place depends exclusively on the probability and relative intensity
of fire. We may assume that most rainforest stands eventually
will burn, even without human disturbance. Thus, the protection
of rainforest is not concerned with the presence or absence of
disturbance. Rather, management of the spatial and temporal patterns
of disturbance is at issue.
Coping with uncertainty is a key factor in the sustainable management
of forests. Forest managers must accommodate differing levels
of uncertainty concerning both the expected timber resource and
other forest values (Dennis et al. 1985, Hilborn and Ludwig
1993). The environment is inherently unpredictable and
one would be foolhardy to attempt to predict the impact on any
given patch of rainforest of such processes as fire, disease,
landslip and the interactions of these factors with human activities.
The consequences of human disturbance should be evaluated within
a framework of risk assessment. Within that framework, human
responsibility is to manage the risks that result from both human
activities and other sources. This review will attempt to evaluate
current and proposed protection measures by weighing the costs
of different alternatives against the risks of adverse outcomes.
Attiwill (1994b) argued that natural disturbance regimes should
be used as a model for forest management. Following McCarthy
and Burgman (in press), we would argue that the model for forest
management must reflect the stochastic nature of natural processes.
That is, when managing forests, the properties of the statistical
process that govern the natural disturbance regime are as important
as the average properties of that process. Thus, it is not enough
to know that the average natural disturbance frequency is, say,
every 80 years. We must also know the variance and skewness of
that disturbance regime, both temporally and spatially, to manage
effectively. Management options, in the context of the above
framework, will be judged by the degree to which they affect risks
to rainforest. Similarly, research priorities will be judged
by the degree to which they improve our understanding of impacts
in terms of risks.
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