Suzanne Dobbie
Ecological communities as a unit of conservation
M.Sc. (Env) 1999
As the rate of biodiversity loss continues to increase, various alternatives
to the traditional species-by-species approach to conservation have been developed.
Focusing conservation efforts on higher levels of biological organisation, such
as ecological communities, is thought to overcome the bias towards charismatic
species, and protect undiscovered and lesser-studied species associated with
the community using the limited resources available for conservation more efficiently.
The successful implementation of these approaches relies on clear definitions
being established for typically ambiguous ecological terms, including "ecological
community". The definition "the collection of species that occur in
time and space" was deemed the most effective as it acknowledges the temporal
and spatial variability inherent in natural systems. In Australia, endangered
communities can be protected under Federal, ACT, Victorian and NSW legislation.
The Threatened Species Conservation Act 1995 (TSC Act) currently lists nineteen endangered communities, eighteen of which are plant-based assemblages. This study compared the arthropod assemblages of two communities, Blue Gum High Forest which is protected under the TSC Act, and the relatively common Blackbutt-Turpentine Forest. These communities have a similar floristic composition and structure, but are defined as different communities based on their dominant canopy species. Results of a snapshot survey showed there was no significant difference in the assemblages of ants, flies, spiders and wasps collected from the two communities. A range of variables (density of trees, understorey cover, anthropogenic disturbance, years since fire, distance between sites, and areas of sites) were measured to test whether they could predict the assemblage of arthropods surveyed. Again, no significant results were obtained. The lack of spatial fidelity among remnants of the same community means that urban remnant vegetation is unlikely to be a useful surrogate for arthropods that utilise these remnants. This trend is likely to be repeated in other fragmented communities, and spatial and temporal fidelity needs to be tested in other communities listed under the TSC Act such as the Cumberland Plain Woodlands and Eastern Suburbs Banksia Scrub which have undergone marked changes in community structure and composition due to the pressures of urbanisation. These results do not diminish the value of conserving communities, but indicate protecting communities defined by a suite of core species does not ensure the survival of other biota.