Thresholds, incidence functions, and species-specific cues : responses of woodland birds to landscape structure in south-eastern Australia

Looking out from a vantage point across a large tract of forest gives a superficial impression of uniformity: the crowns of canopy trees follow the folds and contours of the landscape to provide a continuous cover of wooded vegetation. But this visual appearance belies the truth: forested landscapes are far from uniform. On closer examination, they comprise a complex mosaic of different vegetation types and and stands of different age-classes, differing structural features, and modified to a varying extent by human land-uses. Forests have a critical role in the conservation of biodiversity throughout the world (Peterken 1996; Laurance and Bierregard 1997; Lindenmayer and Franklin 2002) and a key feature contributing to their conservation value is the response of forest biota to the heterogeneity inherent in forested landscapes (Lindenmayer et al. 2006). Consequently, an understanding of the implications of landscape structure for the maintainance of species and ecological processes is an important foundation for forest management and biodiversity conservation.

Bioregional planning

The study investigated the appropriateness of bioregional planning as a preferential framework for better integrating land-use planning and natural resource management and found it may be appropriate in Victoria for improved biodiversity conservation. Main issues impeding wider implementation include poor Government coordination and historic cultural attitudes between the two professions.

Sooty owl ecology and recent small mammal decline

This thesis investigated the ecology of the threatened sooty owl, which was used to improve understanding of recent small mammal declines and how a top-order predator adapted to changes in ecosystem condition following European settlement. This knowledge will help improve biodiversity conservation and management of forested ecosystems in south-eastern Australia.

Fire, energy, and the ecology of reptiles in semi-arid Australia

‬Fire dependent ecosystems cover over half of the world's land surface. Understanding the factors that determine the distribution of fauna in these systems is essential to biodiversity conservation. This thesis explores the ecology of reptiles in a fire-prone region.

The disappearing mammal fauna of northern Australia : context, cause, and response

This article provides a context to, attempts an explanation for, and proposes a response to the recent demonstration of rapid and severe decline of the native mammal fauna of Kakadu National Park. This decline is consistent with, but might be more accentuated than, declines reported elsewhere in northern Australia; however, such a comparison is constrained by the sparse information base across this region. Disconcertingly, the decline has similarities with the earlier phase of mammal extinctions that occurred elsewhere in Australia. We considered four proximate factors (individually or interactively) that might be driving the observed decline: habitat change, predation (by feral cats), poisoning (by invading cane toads), and novel disease. No single factor readily explains the current decline. The current rapid decline of mammals in Kakadu National Park and northern Australia suggests that the fate of biodiversity globally might be even bleaker than evident in recent reviews, and that the establishment of conservation reserves alone is insufficient to maintain biodiversity. This latter conclusion is not new; but the results reported here further stress the need to manage reserves far more intensively, purposefully, and effectively, and to audit regularly their biodiversity conservation performance.

Demonising the dingo : how much wild dogma is enough?

The roles that top predators play in regulating the structure and function of ecosystems have long been controversial. This is particularly the case when predators pose adverse risks for human life and/or economic interests. The critique of literature on dingoes and their ecological roles in Australia provided by Allen et al. (2011) shows that top predators remain a potentially polarising issue. In opposition to Allen et al. we argue that these widespread patterns of species’ abundances, attributed to the effects of dingoes and evident at scales ranging from the foraging behaviour of individuals through to continental scale patterns of species abundances, constitute strong support for the mesopredator release hypothesis and provide evidence that dingoes benefit biodiversity conservation by inducing community wide trophic cascades. Harnessing the positive ecological effects of dingoes while at the same time minimising their impacts on agriculture is a major socio-political challenge in Australia [Current Zoology 57 (5): 668-670].

Hybridization of Southern Hemisphere blue whale subspecies and a sympatric area off Antarctica : impacts of whaling or climate change?

Understanding the degree of genetic exchange between subspecies and populations is vital for the appropriate management of endangered species. Blue whales (Balaenoptera musculus) have two recognized Southern Hemisphere subspecies that show differences in

Weeds and wildlife: perceptions and practices of weed managers

Negative impacts of invasive plants or weeds on biodiversity have been well established yet their role in providing key habitats and resources for wildlife has been little understood. Weed removal thus has the potential to adversely affect wildlife but whether this is considered during weed management is poorly known. To determine the extent of this knowledge, we examined the perceptions of weed managers regarding wildlife and weed management in Victoria, Australia. We surveyed 81 weed managers of varying levels of experience from different types of organisations, including state and local government, community groups and private companies. We found 90% of managers had observed wildlife-weed interactions and that most (70%) adjusted management programmes to accommodate wildlife. Despite this, few (19%) had adopted the recommended practice of combining gradual weed removal with re-vegetation. While management programmes included monitoring of native vegetation, consideration of wildlife monitoring in weed management was rare. This highlights the need for management to better understand and respond to wildlife-weed relationships. If the improvement of wildlife habitat is included in the objectives of weed programmes, as it should be, then wildlife should also be incorporated in project monitoring. This would lead to a greater understanding of the role weeds and their management have in each situation and, ultimately, more informed decision making. Copyright: © Carlos et al. 2014.

Does urbanization have the potential to create an ecological trap for powerful owls (Ninox strenua)?

Landscape transformation associated with urbanization is one of the most damaging and pervasive impacts humans have on natural ecosystems. The response of species to increasing urbanization has become a major focus of research globally. Powerful owls ( Ninox strenua) are a top-order predator the have been shown to reside in urban environments, but increasing urbanization has also been demonstrated to significantly reduce available habitat. In this paper we use species distribution models established for key food and nesting resources of powerful owls across an urban-forest gradient to constrain habitat predictions from a previously developed powerful owl species distribution model. This multi-criteria decision analysis (MCDA) approach allowed us to investigate the impacts of urbanization on potential powerful owl habitat when challenged with food and nesting requirements. As powerful owls only use tree cavities for nesting we propose that the cue for settlement in an area is associated with the presence of habitat and food and as such breeding requirements may be disconnected from settlement requirements.Our results demonstrate that incorporation of a general prey resource (at least one group of arboreal marsupials) as a cue for settlement does not reduce the amount of available habitat for powerful owls substantially. Further constraining the model with a tree cavity resource, however, leads to a substantial reduction in powerful owl habitat in the urban and urban fringe environments. If a diverse prey resource (two or more groups of arboreal marsupials) is used as the cue for settlement, this sees a substantial reduction in available habitat in urban environments. Incorporation of tree cavities into this model does not reduce the available habitat for powerful owls substantially.We propose that powerful owls do not need a diverse prey base for survival, and that breeding resources are unlikely to be a cue for settlement. As such, we argue in this paper that increasing urbanization has the potential to create an ecological trap for powerful owls as there is a significant difference between habitat capable of supporting powerful owls, and habitat in which owls can breed.Management of powerful owls in urban environments will be difficult, but this research highlights the potential for the use of nest boxes to enhance the breeding activities in increasingly urbanized environments. Replacement of this critical resource may be able to reverse any potential ecological trap that is occurring. © 2014 Elsevier Ltd.

Predicting the likely response of data-poor ecosystems to climate change using space-for-time substitution across domains

Predicting ecological response to climate change is often limited by a lack of relevant local data from which directly applicable mechanistic models can be developed. This limits predictions to qualitative assessments or simplistic rules of thumb in data-poor regions, making management of the relevant systems difficult. We demonstrate a method for developing quantitative predictions of ecological response in data-poor ecosystems based on a space-for-time substitution, using distant, well-studied systems across an inherent climatic gradient to predict ecological response. Changes in biophysical data across the spatial gradient are used to generate quantitative hypotheses of temporal ecological responses that are then tested in a target region. Transferability of predictions among distant locations, the novel outcome of this method, is demonstrated via simple quantitative relationships that identify direct and indirect impacts of climate change on physical, chemical and ecological variables using commonly available data sources. Based on a limited subset of data, these relationships were demonstrably plausible in similar yet distant (>2000 km) ecosystems. Quantitative forecasts of ecological change based on climate-ecosystem relationships from distant regions provides a basis for research planning and informed management decisions, especially in the many ecosystems for which there are few data. This application of gradient studies across domains - to investigate ecological response to climate change - allows for the quantification of effects on potentially numerous, interacting and complex ecosystem components and how they may vary, especially over long time periods (e.g. decades). These quantitative and integrated long-term predictions will be of significant value to natural resource practitioners attempting to manage data-poor ecosystems to prevent or limit the loss of ecological value. The method is likely to be applicable to many ecosystem types, providing a robust scientific basis for estimating likely impacts of future climate change in ecosystems where no such method currently exists.

Does fire influence the landscape-scale distribution of an invasive mesopredator?

Predation and fire shape the structure and function of ecosystems globally. However, studies exploring interactions between these two processes are rare, especially at large spatial scales. This knowledge gap is significant not only for ecological theory, but also in an applied context, because it limits the ability of landscape managers to predict the outcomes of manipulating fire and predators. We examined the influence of fire on the occurrence of an introduced and widespread mesopredator, the red fox (Vulpes vulpes), in semi-arid Australia. We used two extensive and complimentary datasets collected at two spatial scales. At the landscape-scale, we surveyed red foxes using sand-plots within 28 study landscapes - which incorporated variation in the diversity and proportional extent of fire-age classes - located across a 104 000 km2 study area. At the site-scale, we surveyed red foxes using camera traps at 108 sites stratified along a century-long post-fire chronosequence (0-105 years) within a 6630 km2 study area. Red foxes were widespread both at the landscape and site-scale. Fire did not influence fox distribution at either spatial scale, nor did other environmental variables that we measured. Our results show that red foxes exploit a broad range of environmental conditions within semi-arid Australia. The presence of red foxes throughout much of the landscape is likely to have significant implications for native fauna, particularly in recently burnt habitats where reduced cover may increase prey species' predation risk.

Resistance and resilience: Can the abrupt end of extreme drought reverse avifaunal collapse?

Aim: Climate change is expected to increase the frequency and intensity of extreme climatic events, such as severe droughts and intense rainfall periods. We explored how the avifauna of a highly modified region responded to a 13-year drought (the 'Big Dry'), followed by a two-year period of substantially higher than average rainfall (the 'Big Wet'). Location: Temperate woodlands in north central Victoria, Australia. Methods: We used two spatially extensive, long-term survey programmes, each of which was repeated three times: early and late in the Big Dry, and in the Big Wet. We compared species-specific changes in reporting rates between periods in both programmes to explore the resistance (the ability to persist during drought) and resilience (extent of recovery post-drought) of species to climate extremes. Results: There was a substantial decline in the reporting rates of 42-62% (depending on programme) of species between surveys conducted early and late in the Big Dry. In the Big Wet, there was some recovery, with 21-29% of species increasing substantially. However, more than half of species did not recover and 14-27% of species continued to decline in reporting rate compared with early on in the Big Dry. Species' responses were not strongly related to ecological traits. Species resistance to the drought was inversely related to resilience in the Big Wet for 20-35% of the species, while 76-78% of species with low resistance showed an overall decline across the study period. Conclusions: As declines occurred largely irrespective of ecological traits, this suggests a widespread mechanism is responsible. Species that declined the most during the Big Dry did not necessarily show the greatest recoveries. In already much modified regions, climate extremes such as extended drought will induce on-going changes in the biota. © 2014 John Wiley & Sons Ltd.

Why do some species have geographically varying responses to fire history?

A capacity to predict the effects of fire on biota is critical for conservation in fire-prone regions as it assists managers to anticipate the outcomes of different approaches to fire management. The task is complicated because species' responses to fire can vary geographically. This poses challenges, both for conceptual understanding of post-fire succession and fire management. We examine two hypotheses for why species may display geographically varying responses to fire. 1) Species' post-fire responses are driven by vegetation structure, but vegetation - fire relationships vary spatially (the 'dynamic vegetation' hypothesis). 2) Regional variation in ecological conditions leads species to select different post-fire ages as habitat (the 'dynamic habitat' hypothesis). Our case study uses data on lizards at 280 sites in a ~ 100 000 km2 region of south-eastern Australia. We compared the predictive capacity of models based on 1) habitat associations, with models based on 2) fire history and vegetation type, and 3) fire history alone, for four species of lizards. Habitat association models generally out-performed fire history models in terms of predictive capacity. For two species, habitat association models provided good discrimination capacity even though the species showed geographically varying post-fire responses. Our results support the dynamic vegetation hypothesis, that spatial variation in relationships between fire and vegetation structure results in regional variation in fauna-fire relationships. These observations explain how the widely recognised 'habitat accommodation' model of animal succession can be conceptually accurate yet predictively weak. © 2014 The Authors.