Abstract The resilience, or sustainability, of an environmental system depends on key factors remaining within critical thresholds. Current approaches to assessing the condition and trend of environmental systems rely on expert knowledge of system performance and subjective interpretation. Computer simulation models of natural resource systems offer a way to integrate system properties, and ecological theory and relationships, with long-term climate and rainfall information to simulate system performance within a consistent framework. Financial accounting methods, such as balance sheets and ratio analysis, have been developed to assess overall businesses viability and offer a potential tool for assessing the sustainability of natural systems, providing key accounting principles and assumptions can be reasonably met. This thesis explores the integration of accounting and ecological theory in a balance sheet framework for sustainability accounting using non-financial terms with a view to contributing to the sustainable management of natural resources within dynamic systems. A generic approach to constructing environmental balance sheets was developed and tested at a range of scales (field to catchment). Sensitivity analysis of the models was used to determine key factors and critical thresholds relating to system resilience. These values were then used to construct the balance sheets. The current ratio was then used to identify if the system was being managed sustainably. A current ratio (assets/liabilities) greater than 1.0, derived from the balance sheet, was shown to denote more resilient, and hence sustainable, systems. Case studies used were wheat cropping in the Maranoa area of Queensland, Australia, and the Bonogin Valley in the Gold Coast, Queensland Australia The same approach to constructing balance sheets worked across all scales from farm to catchment. . The approach was then used to develop a sustainability assessment of the Coomera catchment of the Gold Coast to consider how natural resource management and urbanisation is affecting catchment resilience. A series of models was used to develop the accounts: a grazing systems model – SGS; a cropping systems model - APSIM-sugar; and an existing catchment hydrology and water quality model - EMSS. The approach demonstrated that sugarcane cropping systems within the catchment were not likely to be sustainable without significant input of nitrogen, but that the grazing systems were. Furthermore, the overall catchment was likely to be sustainable (2002). This finding is consistent with an independent field-based assessment of the catchment conducted by the Healthy Waterways Partnership of South East Queensland. The urban development anticipated in the catchment by 2020, did not appear to have a significant affect as measured by long-term trends in flow frequency and water quality. The use of ratio analysis provided a dimensionless variable that related to the resilience of a parcel of land or catchment. These values were able to be spatially integrated, using an area weighted median, to provide an overall estimate of resilience of land use for a farm or a catchment. However, it was considered simpler to model the catchment of interest as a whole rather than to combine ratios from a series of catchment sub-models. The availability of appropriate comprehensive systems models may prove a limitation for application to all land uses especially native bushland systems. However, the approach developed in this thesis provides a robust and consistent framework for exploring system resilience and sustainability in a way that can augment existing approaches to natural resource assessments of condition and trend.
| Identifer | oai:union.ndltd.org:ADTP/283962 |
| Creators | Evan Thomas |
| Source Sets | Australiasian Digital Theses Program |
| Detected Language | English |
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