Science Collected Works - Research Publications
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ItemAssessing the sensitivity of biodiversity indices used to inform fire management(WILEY, 2018-03)Biodiversity indices are widely used to summarize changes in the distribution and abundance of multiple species and measure progress towards management targets. However, the sensitivity of biodiversity indices to the data, landscape classification and conservation values underpinning them are rarely interrogated. There are limited studies to help scientists and land managers use biodiversity indices in the presence of fire and vegetation succession. The geometric mean of species' relative abundance or occurrence (G) is a biodiversity index that can be used to determine the mix of post‐fire vegetation that maximizes biodiversity. We explored the sensitivity of G to (1) type of biodiversity data, (2) representation of ecosystem states, (3) expression of conservation values, and (4) uncertainty in species' response to landscape structure. Our case study is an area of fire‐prone woodland in southern Australia where G is used in fire management planning. We analysed three datasets to determine the fire responses of 170 bird, mammal and reptile species. G and fire management targets were sensitive to the species included in the analysis. The optimal mix of vegetation successional states for threatened birds was more narrowly defined than the optimal mix for all species combined. G was less sensitive to successional classification (i.e. number of states); although classifications of increasing complexity provided additional insights into desirable levels of heterogeneity. Weighting species by conservation status or endemism influenced the mix of vegetation states that maximized biodiversity. When a higher value was placed on threatened species the importance of late successional vegetation was emphasized. Representing variation in individual species' response to vegetation structure made it clearer when a decrease in G was likely to reflect a significant reduction in species occurrences. Synthesis and applications. Data, models and conservation values can be combined using biodiversity indices to make robust environmental decisions. Combining different types of biodiversity data using composite indices, such as the geometric mean, can improve the coverage and relevance of biodiversity indices. We recommend that evaluation of biodiversity indices for fire management verify how index assumptions align with management objectives, consider the relative merits of different types of biodiversity data, test sensitivity of ecosystem state definitions and incorporate conservation values through species weightings.
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ItemPutting pyrodiversity to work for animal conservation(WILEY, 2017-08)
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ItemOptimal fire histories for biodiversity conservation(WILEY, 2015-04)Fire is used as a management tool for biodiversity conservation worldwide. A common objective is to avoid population extinctions due to inappropriate fire regimes. However, in many ecosystems, it is unclear what mix of fire histories will achieve this goal. We determined the optimal fire history of a given area for biological conservation with a method that links tools from 3 fields of research: species distribution modeling, composite indices of biodiversity, and decision science. We based our case study on extensive field surveys of birds, reptiles, and mammals in fire-prone semi-arid Australia. First, we developed statistical models of species' responses to fire history. Second, we determined the optimal allocation of successional states in a given area, based on the geometric mean of species relative abundance. Finally, we showed how conservation targets based on this index can be incorporated into a decision-making framework for fire management. Pyrodiversity per se did not necessarily promote vertebrate biodiversity. Maximizing pyrodiversity by having an even allocation of successional states did not maximize the geometric mean abundance of bird species. Older vegetation was disproportionately important for the conservation of birds, reptiles, and small mammals. Because our method defines fire management objectives based on the habitat requirements of multiple species in the community, it could be used widely to maximize biodiversity in fire-prone ecosystems.
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ItemA systematic review reveals changes in where and how we have studied habitat loss and fragmentation over 20 years(ELSEVIER SCI LTD, 2017-08)Habitat loss and fragmentation are global threats to biodiversity and major research topics in ecology and conservation biology. We conducted a systematic review to assess where – the geographic locations and habitat types - and how – the study designs, conceptual underpinnings, landscape metrics and biodiversity measures - scientists have studied fragmentation over the last two decades. We sampled papers from 1994 to 2016 and used regression modelling to explore changes in fragmentation research over time. Habitat loss and fragmentation studies are geographically and taxonomically biased. Almost 85% of studies were conducted in America and Europe, with temperate forests and birds the most studied groups. Most studies use a binary conceptual model of landscapes (habitat versus non-habitat) and static measures of biodiversity. However, research on fragmentation is slowly shifting from a focus on coarse patterns to more nuanced representations of biodiversity and landscapes that better represent ecological processes. For example, empirical research based on gradient or continuum models, that offer new insights into landscape complexity and species-specific responses to habitat fragmentation, are increasing in prevalence. We recommend that fragmentation research focuses on developing knowledge on underlying mechanisms and processes of how species respond to landscape changes, and that fragmentation studies be conducted in the full range of habitats currently experiencing high rates of landscape modification. This is crucial if we are to understand relationships between biodiversity and ecosystems and to develop effective management strategies in fragmented landscapes.
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ItemInteractions between rainfall, fire and herbivory drive resprouter vital rates in a semi-arid ecosystem(WILEY, 2017-11)Summary Global change is threatening ecosystems and biodiversity world‐wide, creating a pressing need to understand how climate and disturbance regimes interact and influence the persistence of species. We quantify how three ecosystem drivers – rainfall, fire and herbivory – influence vital rates in the perennial resprouting graminoid, Triodia scariosa, a foundation species of semi‐arid Australia. We used an 11‐year dataset from a fire and herbivore exclosure experiment, to model flowering, post‐fire recruitment and the post‐fire survival of seedlings and resprouting plants. Regression modelling quantified the effect of rainfall, inter‐fire interval, fire type (wildfire or prescribed fire), grazing by herbivores (native and feral) and an interaction between fire type and herbivory on T. scariosa populations. Rainfall, fire and herbivory had significant effects on post‐fire recruitment and the survival of seedlings and resprouting plants, including strong interactions between these drivers. Herbivory following wildfire had a minor effect, but in years of below‐average rainfall herbivory following prescribed fire had a large effect, reducing the survival of seedlings and resprouting plants by 20% and over 50% respectively, relative to post‐fire survival under average rainfall conditions. Variation in rainfall underpinned significant variation in post‐fire resprouting and seedling survival, thus we postulate rainfall primarily drives the dynamics of T. scariosa populations. Synthesis. This study highlights the importance of modelling interactions between key ecosystem drivers when predicting how changes in global climate and disturbance regimes influence plant vital rates. Relatively small changes to disturbance regimes can substantially alter population processes, even in perennial resprouting species. This work suggests that conservation of foundation species, such as T. scariosa, will benefit if fire management decisions are better integrated with inter‐annual weather forecasts and herbivore management.