The risk of each of the threatening processes on the threatened species and ecological communities and the landscape units of the Fitzgerald Biosphere was determined to allow the recovery actions and management practices of this Plan to be focused where they are most needed.
Method of Determining Risk for Threatened Species and Ecological Communities
Analysis and ranking of the risk of threatening processes on the threatened species and ecological communities was undertaken using the Open Standards of the Practice of Conservation guidelines and the adaptive management software Miradi (CMP 2009). This involved assessing the risk of each of the threatening processes for each of the threatened species/communities over the next 10 years based on three criteria:
Scope (proportion of population expected to be affected),
Severity (the degree to which the population is expected to be affected), and
Irreversibility (degree to which the effects can be reversed).
Further details of this ranking process using Miradi is included in Appendix 6. The analysis and ranking of threats was based on best available knowledge and current understanding of impacts from individual threatening processes upon the threatened species and ecological communities.
The risk ratings for each of the threatened fauna, flora and ecological community to each of the threats in the Fitzgerald Biosphere are shown in Table 9 and Table. These ratings relate to the magnitude of the threat to the species/communities and its reversibility over the 10 year timeframe of this Plan.
The risk ratings show that inappropriate fire regimes and predation by feral cats and foxes are the most significant threats to threatened fauna in the Biosphere, followed by loss of habitat, fragmentation and degradation, stochastic events and climate change (Table 9).
Phytophthora cinnamomi is ranked as a low threat for most of the threatened fauna species, except the Dibbler for which it is a medium threat as it occurs in habitat dominated by susceptible flora species. P. cinnamomi is not considered a threat to the Red-tailed Phascogale or Numbat. However, P. cinnamomi is considered a very significant threat in the Biosphere due to its significant impact to biodiversity overall and because it cannot be eradicated.
Overall these risk ratings show that all the threatened fauna species were ranked as high to very high risk in the Fitzgerald Biosphere, except the Chuditch and the Numbat which have a medium rating. The Western Ground Parrot is the most at risk due to its small population size.
Table 9: Risk ratings for each of the threatened fauna species to each of the most significant threats in the Fitzgerald Biosphere over then next 10 years, as determined using Miradi (CMP 2009). These ratings are based on three criteria: Scope, Severity and Irreversibility (Appendix 6). Blank = not considered a significant threat to that species.
The risk ratings show that inappropriate fire and climate change are the most significant threats to threatened flora and the ecological community in the Biosphere (Table 10). Climate change is a significant threat for many of the flora species due to small population sizes, and that they rely on specific habitats (e.g. the tops of the hills of the Barren Range) that are likely to be highly impacted by any changes in temperature or rainfall.
Phytophthora cinnamomi is ranked as a low to high threat and is not a threat for nine of the threatened flora species. These rankings were made with the assumption that P. cinnamomi will not become widespread in the Biosphere in the next 10 years, but because it cannot be eradicated from where it does spread, it is considered a very significant threat in the Biosphere.
The risk of the threatening processes in the Fitzgerald Biosphere are unknown for Conostylis lepidospermiodes and Lepidium aschersonii, as these species have not been seen in the Fitzgerald Biosphere in recent years (Appendix 2).
Table10: Risk ratings for each of the threatened flora species and the ecological community to each of the most significant threatening processes in the Fitzgerald Biosphere over then next 10 years, as determined using Miradi (CMP 2009). These ratings are based on three criteria: Scope, Severity and Irreversibility (Appendix 6). Blank = not considered a significant threat.
Susceptibility of the Landscape Units of the Fitzgerald Biosphere to significant threats are summarised in Table11. Risk of the threats were not ranked using Miradi due to the complexity of the Landscape Units. Each Landscape Unit responds differently to threatening processes due to different physical characteristics and these differences need to be understood when considering threat abatement.
Table11: The most significant threatening processes and susceptibility to these threats of each of the Landscape Units of the Fitzgerald Biosphere.
Threats specific to Landscape Unit
(including current level of threat within landscape units plus potential threats based on specific susceptibility of the unit to threat)
Albany Fraser Coastal
Stable system - sensitive to frequent disturbance
Climate change (species at edge of range, restricted, endemic)
Phytophthora (highly susceptible flora and vegetation communities)
Highly dynamic system - adapted to frequent ground disturbance