400 Monitoring Threatened Species and Ecological Communities
AM is rarely employed in the conservation of threatened species. To illustrate
some of the potential reasons for this, a case study is presented from the Critically
Endangered mountain ash Eucalyptus regnans forests ecosystems of the Central
Highlands of Victoria. These forests are important habitat for populations of the
Critically Endangered Leadbeater’s possum, Gymnobelidues leadbeateri.
Case study – adaptive management of the mountain ash
ecosystem
Clearfell logging of the mountain ash forests of Victoria has long been
controversial, with its effects on threatened species such as Leadbeater’s possum
being a particular concern (Warneke 1968; Lindenmayer et al. 2015b). One
proposed way to reduce some of the environmental impacts is to employ alternative
forms of logging to clearfelling, such as the variable retention harvest system
(Fedrowitz et al. 2014), in which parts of harvested stands are left unlogged in
order to leave existing and potential future habitat for biodiversity (Fig. 32.2). A
proposal to implement the variable retention harvesting system as an AM
experiment in Victorian wet ash forests was developed during an international
forestry roundtable meeting held in central Victoria in late 2002 (Lindenmayer and
Franklin 2003). The meeting involved all key conservation, forestry and industry
stakeholders and a pathway was set to implement the experiment involving the
series of steps outlined in the Introduction of this chapter. In particular, the
prospect for using the experiment to help promote the development of suitable
habitat in the medium to long term for Leadbeater’s possum was a key
consideration (Lindenmayer and Franklin 2003). Conceptual models were
developed to predict how the ecosystem and various groups of vertebrate biota
might respond to the experiment. A rigorous blocked and replicated experimental
design was developed in close collaboration with an expert panel of statistical
scientists. The experiment comprised four treatments in each of seven
experimental blocks (each of ~1000 ha in size): (1) unlogged controls; (2)
conventional clearfelled areas; (3) an area cut using the variable retention
harvesting system with three small (0.5 ha) islands of retained forest; and (4) an
area cut using the variable retention harvesting system with one large (1.5 ha)
island of retained forest.
Although the initial motivation for the experiment centred around habitat
protection/creation for the Critically Endangered Leadbeater’s possum, it became
clear that prescriptions preventing the logging of potential habitat for the species
precluded the possum (and other threatened arboreal marsupials) from being
included in the experiment. The research focus was therefore switched to small
mammals and forest birds as indicators of biodiversity response to management
interventions. Field work entailed quantifying small mammal and bird occurrence