Leonie Seabrook

Wildlife disease prevalence in human-modified landscapes

Human‐induced landscape change associated with habitat loss and fragmentation places wildlife populations at risk. One issue in these landscapes is a change in the prevalence of disease which may result in increased mortality and reduced fecundity. Our understanding of the influence of habitat loss and fragmentation on the prevalence of wildlife diseases is still in its infancy. What is evident is that changes in disease prevalence as a result of human‐induced landscape modification are highly variable. The importance of infectious diseases for the conservation of wildlife will increase as the amount and quality of suitable habitat decreases due to human land‐use pressures. We review the experimental and observational literature of the influence of human‐induced landscape change on wildlife disease prevalence, and discuss disease transmission types and host responses as mechanisms that are likely to determine the extent of change in disease prevalence. It is likely that transmission dynamics will be the key process in determining a pathogens impact on a host population, while the host response may ultimately determine the extent of disease prevalence. Finally, we conceptualize mechanisms and identify future research directions to increase our understanding of the relationship between human‐modified landscapes and wildlife disease prevalence. This review highlights that there are rarely consistent relationships between wildlife diseases and human‐modified landscapes. In addition, variation is evident between transmission types and landscape types, with the greatest positive influence on disease prevalence being in urban landscapes and directly transmitted disease systems. While we have a limited understanding of the potential influence of habitat loss and fragmentation on wildlife disease, there are a number of important areas to address in future research, particularly to account for the variability in increased and decreased disease prevalence. Previous studies have been based on a one‐dimensional comparison between unmodified and modified sites. What is lacking are spatially and temporally explicit quantitative approaches which are required to enable an understanding of the range of key causal mechanisms and the reasons for variability. This is particularly important for replicated studies across different host‐pathogen systems. Furthermore, there are few studies that have attempted to separate the independent effects of habitat loss and fragmentation on wildlife disease, which are the major determinants of wildlife population dynamics in human‐modified landscapes. There is an urgent need to understand better the potential causal links between the processes of human‐induced landscape change and the associated influences of habitat fragmentation, matrix hostility and loss of connectivity on an animals physiological stress, immune response and disease susceptibility. This review identified no study that had assessed the influence of human‐induced landscape change on the prevalence of a wildlife sexually transmitted disease. A better understanding of the various mechanisms linking human‐induced landscape change and the prevalence of wildlife disease will lead to more successful conservation management outcomes.

Drought-driven change in wildlife distribution and numbers: a case study of koalas in south west Queensland

Context Global climate change will lead to increased climate variability, including more frequent drought and heatwaves, in many areas of the world. This will affect the distribution and numbers of wildlife populations. In south-west Queensland, anecdotal reports indicated that a low density but significant koala population had been impacted by drought from 2001–2009, in accord with the predicted effects of climate change. Aims The study aimed to compare koala distribution and numbers in south-west Queensland in 2009 with pre-drought estimates from 1995–1997. Methods Community surveys and faecal pellet surveys were used to assess koala distribution. Population densities were estimated using the Faecal Standing Crop Method. From these densities, koala abundance in 10 habitat units was interpolated across the study region. Bootstrapping was used to estimate standard error. Climate data and land clearing were examined as possible explanations for changes in koala distribution and numbers between the two time periods. Key results Although there was only a minor change in distribution, there was an 80% decline in koala numbers across the study region, from a mean population of 59 000 in 1995 to 11 600 in 2009. Most summers between 2002 and 2007 were hotter and drier than average. Vegetation clearance was greatest in the eastern third of the study region, with the majority of clearing being in mixed eucalypt/acacia ecosystems and vegetation on elevated residuals. Conclusions Changes in the area of occupancy and numbers of koalas allowed us to conclude that drought significantly reduced koala populations and that they contracted to critical riparian habitats. Land clearing in the eastern part of the region may reduce the ability of koalas to move between habitats. Implications The increase in hotter and drier conditions expected with climate change will adversely affect koala populations in south-west Queensland and may be similar in other wildlife species in arid and semiarid regions. The effect of climate change on trailing edge populations may interact with habitat loss and fragmentation to increase extinction risks. Monitoring wildlife population dynamics at the margins of their geographic ranges will help to manage the impacts of climate change.

Biodiversity Risks from Fossil Fuel Extraction

The overlapping of biodiverse areas and fossil fuel reserves indicates high-risk regions. Despite a global political commitment to reduce biodiversity loss by 2010 through the 2002 Convention on Biological Diversity, declines are accelerating and threats are increasing (1). Major threats to biodiversity are habitat loss, invasion by exotic species and pathogens, and climate change, all principally driven by human activities. Although fossil fuel (FF) extraction has traditionally been seen as a temporary and spatially limited perturbation to ecosystems (2), even local or limited biodiversity loss can have large cascade effects on ecosystem function and productivity. We explore the overlap between regions of high marine and terrestrial biodiversity and FF reserves to identify regions at particular risk of ecosystem destruction and biodiversity loss from exposure to FF extraction.

Integrating plant- and animal- based perspectives for more effective restoration of biodiversity

Ecological restoration of modified and degraded landscapes is an important challenge for the 21st century, with potential for major gains in the recovery of biodiversity. However, there is a general lack of agreement between plant- and animal-based approaches to restoration, both in theory and practice. Here, we review these approaches, identify limitations from failing to effectively integrate their different perspectives, and suggest ways to improve outcomes for biodiversity recovery in agricultural landscapes. We highlight the need to strengthen collaboration between plant and animal ecologists, to overcome disciplinary and cultural differences, and to achieve a more unified approach to restoration ecology. Explicit consideration of key ecosystem functions, the need to plan at multiple spatial and temporal scales, and the importance of plant–animal interactions can provide a bridge between plant- and animal-based methods. A systematic approach to restoration planning is critical to achieving effective biodiversity outcomes while meeting long-term social and economic needs.

Cascading effects of climate extremes on vertebrate fauna through changes to low-latitude tree flowering and fruiting phenology.

Forest vertebrate fauna provide critical services, such as pollination and seed dispersal, which underpin functional and resilient ecosystems. In turn, many of these fauna are dependent on the flowering phenology of the plant species of such ecosystems. The impact of changes in climate, including climate extremes, on the interaction between these fauna and flora has not been identified or elucidated, yet influences on flowering phenology are already evident. These changes are well documented in the mid to high latitudes. However, there is emerging evidence that the flowering phenology, nectar/pollen production, and fruit production of long-lived trees in tropical and subtropical forests are also being impacted by changes in the frequency and severity of climate extremes. Here, we examine the implications of these changes for vertebrate fauna dependent on these resources. We review the literature to establish evidence for links between climate extremes and flowering phenology, elucidating the nature of relationships between different vertebrate taxa and flowering regimes. We combine this information with climate change projections to postulate about the likely impacts on nectar, pollen and fruit resource availability and the consequences for dependent vertebrate fauna. The most recent climate projections show that the frequency and intensity of climate extremes will increase during the 21st century. These changes are likely to significantly alter mass flowering and fruiting events in the tropics and subtropics, which are frequently cued by climate extremes, such as intensive rainfall events or rapid temperature shifts. We find that in these systems the abundance and duration of resource availability for vertebrate fauna is likely to fluctuate, and the time intervals between episodes of high resource availability to increase. The combined impact of these changes has the potential to result in cascading effects on ecosystems through changes in pollinator and seed dispersal ecology, and demands a focused research effort.

Can a problem-solving approach strengthen landscape ecology’s contribution to sustainable landscape planning?

The need to avert unacceptable and irreversible environmental change is the most urgent challenge facing society. Landscape ecology has the capacity to help address these challenges by providing spatially-explicit solutions to landscape sustainability problems. However, despite a large body of research, the real impact of landscape ecology on sustainable landscape management and planning is still limited. In this paper, we first outline a typology of landscape sustainability problems which serves to guide landscape ecologists in the problem-solving process. We then outline a formal problem-solving approach, whereby landscape ecologists can better bring about disciplinary integration, a consideration of multiple landscape functions over long time scales, and a focus on decision making. This framework explicitly considers multiple ecological objectives and socio-economic constraints, the spatial allocation of scarce resources to address these objectives, and the timing of the implementation of management actions. It aims to make explicit the problem-solving objectives, management options and the system understanding required to make sustainable landscape planning decisions. We propose that by adopting a more problem-solving approach, landscape ecologists can make a significant contribution towards realising sustainable future landscapes.

Landscape legacies: Koala habitat change in Noosa Shire, South-east Queensland

Present day Australian landscapes are legacies of our colonial history, while future landscapes will be legacies of ecological processes and human impacts occurring today. This paper investigates the legacies of European settlement of Noosa Shire, South-east Queensland, with particular emphasis on the economic and political drivers and the resultant loss and fragmentation of Koala Phascolarctos cinereus habitat. Patterns of habitat loss between 1860 and 1970 were quantified at a coarse level from historical and land tenure records, while changes over the past 30 years were mapped at a finer spatial resolution from aerial photography and satellite imagery. Periods of high economic growth and to lesser extents depression are linked to increased vegetation clearing. Fifty per cent of P. cinereus habitat has been lost since 1860, with habitat class 2A (30-<50 per cent of preferred habitat trees) and 2C (10-<30 per cent of preferred habitat trees) suffering the highest proportion of loss. The period of greatest habitat loss was between 1890 and 1910, linked to the development of the dairy industry in the western half of Noosa Shire. A second significant phase of loss occurred since 1970, linked to the planting of exotic pine plantations, urbanisation and rural subdivision, with 35 per cent of remaining habitat being cleared, mainly in the southern part of the Shire. The cumulative loss of habitat has been accompanied by increasing levels of habitat fragmentation indicated by reduced patch size and increased patch linearity. Further analysis of the temporal aspects of habitat change is required in order to test the hypothesis that there is a relaxation period between the timing of habitat loss and current pattern of habitat occupancy of P. cinereus populations.

Physiological stress in koala populations near the arid edge of their distribution.

Recent research has shown that the ecology of stress has hitherto been neglected, but it is in fact an important influence on the distribution and numbers of wild vertebrates. Environmental changes have the potential to cause physiological stress that can affect population dynamics. Detailed information on the influence of environmental variables on glucocorticoid levels (a measure of stress) at the trailing edge of a species’ distribution can highlight stressors that potentially threaten species and thereby help explain how environmental challenges, such as climate change, will affect the survival of these populations. Rainfall determines leaf moisture and/or nutritional content, which in turn impacts on cortisol concentrations. We show that higher faecal cortisol metabolite (FCM) levels in koala populations at the trailing arid edge of their range in southwestern Queensland are associated with lower rainfall levels (especially rainfall from the previous two months), indicating an increase in physiological stress when moisture levels are low. These results show that koalas at the semi-arid, inland edge of their geographic range, will fail to cope with increasing aridity from climate change. The results demonstrate the importance of integrating physiological assessments into ecological studies to identify stressors that have the potential to compromise the long-term survival of threatened species. This finding points to the need for research to link these stressors to demographic decline to ensure a more comprehensive understanding of species’ responses to climate change.

The effect of ACTH upon faecal glucocorticoid excretion in the koala.

Environmental changes result in physiological responses of organisms, which can adversely affect population dynamics and reduce resistance to disease. These changes are expressed in chronic levels of stress. The measurement of glucocorticoid (GC) concentrations in faeces is a non-invasive method for monitoring stress in wildlife. The metabolism and excretion of steroids differ significantly between species and, as a consequence, non-invasive methods must be physiologically validated for each species. Koalas (Phascolarctos cinereus) are declining in numbers through much of their range. The role of chronic stress in koala populations has not been identified. Prior to the assessment of faecal GC concentrations in wild koala populations, the excretion timing and concentrations of GCs need to be determined. In this study, we assessed a method for identifying and measuring the concentrations of GC metabolites in faecal pellets of captive koalas following ACTH treatment. The results show that an elevation of plasma cortisol concentrations, using sustained release of ACTH, results in elevated concentrations of faecal cortisol/cortisol metabolites. Taking into account the excretion time lag, an increase in faecal cortisol metabolite concentrations corresponds to the release of GCs from the adrenal cortex as early as 36 h before faecal pellet collection. The calculations of steroid partitioning of plasma cortisol showed that the ACTH-stimulated values were significantly different from the control values for the concentrations of free, corticosteroid-binding globulin-bound and albumin-bound cortisol. This study validates the use of faecal cortisol analysis to assess the activity of the hypothalamo-pituitary-adrenocortical axis in freshly collected koala faecal pellets and indicates that the method should be suitable to assess the adrenocortical status of koalas in wild populations.

Transformational change: creating a safe operating space for humanity

Many ecologists and environmental scientists witnessing the scale of current environmental change are becoming increasingly alarmed about how humanity is pushing the boundaries of the Earths systems beyond sustainable levels. The world urgently needs global society to redirect itself toward a more sustainable future: one that moves intergenerational equity and environmental sustainability to the top of the political agenda, and to the core of personal and societal belief systems. Scientific and technological innovations are not enough: the global community, individuals, civil society, corporations, and governments, need to adjust their values and beliefs to one in which sustainability becomes the new global paradigm society. We argue that the solution requires transformational change, driven by a realignment of societal values, where individuals act ethically as an integral part of an interconnected society and biosphere. Transition management provides a framework for achieving transformational change, by giving special attention to reflective learning, interaction, integration, and experimentation at the level of society, thereby identifying the system conditions and type of changes necessary for enabling sustainable transformation.