School of Botany - Theses
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ItemDecision analysis for threatened species management across the captive-wild spectrum( 2015)Programs for the recovery of threatened species increasingly involve active management of variable intensity, such as captive breeding, reintroduction and translocation. Managers of such programs thus need to make decisions about whether and how to implement a given type of management, usually in the face of uncertainty and constraints. Structured decision making provides decision makers with a theoretical framework and practical methods to make rational decisions under uncertainty. In this thesis, I investigate how different principles and tools of structured decision making can assist decisions in threatened species management. The fundamental decision problems in threatened species management concern whether and how to implement a given type of management for the target species. In Chapter 2, I examine the case of whether the conservation of a species should incorporate ex-situ management, using the recovery plan for an endangered frog species in south-eastern Australia as an example. I demonstrate that this question can only be answered rationally after determining how the ex-situ component will benefit the overarching objectives of the recovery plan. This logical sequence of decisions (how before whether) is however followed only infrequently in real-world conservation. I illustrate how managers can implement it with the aid of decision trees and multi-criteria decision analysis. Since decisions are aimed at achieving objectives, they necessarily reflect the values and preferences of stakeholders. Using value functions, in Chapter 2 I demonstrate how the optimal decision depends on the relative importance attributed to different objectives (for example, maximising the probability of persistence of the target species and meeting budget limitations). In Chapter 3, I expand this analysis to demonstrate how to account for the attitude of decision makers towards the risk of negative outcomes. I use two case studies of recovery plans for threatened frog species to illustrate the application of stochastic dominance, a useful method to rank alternative actions in the face of uncertainty and risk. Structured decision making provides methods to make decisions under uncertainty. However, in some instances reducing the existing uncertainty by collecting additional information can allow more robust decisions. As a result, managers of threatened species programs almost always advocate further research, in the expectation that it will improve the outcomes of management. In Chapter 4, I apply a formal method to calculate the expected benefit of additional information to two examples in threatened species management. I demonstrate how the value of information is a function of the current knowledge, by the potential to react to new information, and by the effectiveness of the learning process. Value of information analysis can help managers determine whether and how to implement experiments and monitoring programs to improve the ultimate outcomes of management. For several threatened species programs, the scale and speed of the threatening processes often require decisions to be made immediately, leaving no time for formal experimental learning. Adaptive management describes a specific case of structured decision making in which managers learn by monitoring the outcomes of management and adjust actions accordingly. In Chapter 5, I analyse the conditions and challenges that exist to the application of adaptive management in threatened species programs. The temporal scale of such programs is often sufficient to allow managers to collect information and react by updating actions in subsequent time steps. Particularly for programs toward the captive end of the management spectrum, controlled conditions are also favourable for effective learning. Adaptive management requires the ability to clearly structure uncertainty into formal hypotheses, to allow effective and focused monitoring that addresses the most important sources of uncertainty. Most importantly, institutions and stakeholders must be committed and capable of implementing learning. For clearly defined decision problems, structured decision making can draw upon a range of technical approaches to determine optimal management strategies. In Chapter 6, I consider a reintroduction program in which management decisions are complicated by the complex life history of the target species and budget constraints. I combine demographic modelling and cost-effectiveness analysis to identify the optimal rates of translocation between captive and wild populations. This thesis illustrates how the iterative cycle of structured decision making can benefit all stages of the design of management strategies for threatened species conservation. First, it can help managers in thinking clearly about the decision problem, allowing a transparent assessment of subjective preferences and value. It can then ensure an objective evaluation of the available management alternatives, using qualitative or quantitative predictive approaches that explicitly recognise uncertainty. Finally, it can assist in finding solutions to trade-offs and incorporating additional knowledge to allow better decisions.
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ItemRiparian vegetation in an agricultural landscape: assessment and analysis of condition and change( 2013)Vegetation assessment is done using a wide range approaches depending on the assessment aims and constraints. Two approaches to sampling with vastly different targets, designs, and costs, are snapshot (single time period) or longitudinal (multiple time period) studies. Each approach has a range of strengths and weaknesses for vegetation assessment that allow interrogation of different research objectives. The collection and analysis of data within each sampling approach contains an array of challenges for any given study. The research reported here uses a case study of riparian vegetation in northern Victoria, Australia to explore the use of snapshot and longitudinal surveys for understanding riparian vegetation attributes and the effectiveness of different management actions in an agricultural landscape in northern Victoria. Riparian vegetation is a valuable component of the landscape that acts as the interface between aquatic systems and terrestrial environments. Healthy riparian zones are important for maintaining aquatic ecosystems by providing habitat, shade, banks stability, sediment filtration and nutrient processing. They also support terrestrial ecosystems through provision of ecosystem services. Riparian vegetation is valued for agricultural and recreational uses, which has led to high levels of degradation worldwide. In Victoria, extensive clearing and uncontrolled stock access continues to be a major pressure on riparian vegetation condition. The impact of livestock grazing on riparian systems is predominantly negative. There is a global wealth of knowledge on grazing management, but many gaps exist on the effectiveness of management in different systems and the methods used to evaluate this. Field vegetation surveys remain an essential component of conservation management. Riparian vegetation contains gradients in resources, structure and function, which provides a challenge to survey techniques. Therefore, this research used a quantitative sampling approach designed to capture variation along the gradients of distance from the creek edge, distance along the creek and seasonality. These data were used to characterise the variation in vegetation composition across all sites, in order to inform a new method of sampling riparian vegetation based on delimited zones. This zoned approach was then used in combination with published benchmarks of vegetation condition to evaluate livestock grazing management in this system. Vegetation condition assessments record various vegetation attributes as measures of the value, quality or condition of a site. Comparisons to published benchmarks suggested that the study sites had low cover of all native ground cover life forms, especially medium tufted graminoids and herbs. However, tree canopy cover was at or above expected levels for most sites. Results indicated that livestock grazing was associated with an increase in cover of bare ground and exotic annual herbs and a decrease in cover of native shrubs, herbs and native tufted graminoids. In addition, the effects of grazing varied with distance from the creek. Grazing exclusion through fencing and revoking grazing licences may have benefits for native vegetation condition, but the positive effect of grazing on reducing exotic perennial graminoid cover should also be considered. Evaluating management against vegetation change over time is superior to that of a single point in time as it allows identification of the rate and trajectory of change. Assessment of change requires multiple comparable surveys through time but these data are expensive and slow to acquire. In the absence of these data, historical data sets can provide valuable insights into past vegetation condition and structure. However, historical data collection methods that were not designed for the purposes of monitoring change will produce data not directly comparable to data from more detailed methods. The comparison of unequal datasets is common in ecology and many other fields, but the most appropriate method for comparing unequal data sets is not clearly established. This thesis addresses this issue through applying two methods, one existing and one novel, and comparing their performance in predicting vegetation change through time in order to inform management. The two alternative methods used different approaches to reinterpret coarse historical data. The novel method used data calibration via a double sampling approach, whereas existing methods used Bayesian prior distributions. Data calibration was superior to the existing method in two out of three examined vegetation variables. However, calibration methods required more field surveys and more complicated data analysis. Grazing management indicators were as good or better predictors of vegetation change than a selection of site and environmental variables. Fencing and grazing licence changes had varied effects on different vegetation attributes across sites. The data analyses used were effective tools for evaluating change and effects of management, but made uncertain predictions due to high variation between sites and the thorough accounting of data uncertainties in the models used.