Eddie J. B. van Etten

Inter-annual rainfall variability of arid Australia: greater than elsewhere?

Abstract The often espoused view that Australias arid zone experiences more variable rainfall over time than areas of similar climates elsewhere was tested using annual rainfall data from 407 localities spread throughout 14 arid areas, including 68 Australian sites. This represents an updated and more comprehensive analysis than previously completed. Four measures of inter-annual rainfall variability were calculated. Two of these are commonly used in the literature: the variability index (spread of the 90th and 10th percentiles divided by the median rainfall) and the coefficient of variability (standard deviation as a percentage of the mean). In addition, two simpler measures not divided by the average annual rainfall were used: the difference between the 90th and 10th percentiles, and the standard deviation of the mean. Linear relationships between rainfall variability and average annual rainfall enabled analysis of covariance (ANCOVA) to be employed, with appropriate post hoc testing of adjusted means, to determine differences between regions in terms of the various measures of rainfall variability. ANCOVA consistently revealed that four regions (Thar, Namib-Kalahari, Somali and northern Australian deserts) were significantly more variable than all others. Southern Australia (defined as south of 27°S latitude) was grouped with these other desert regions, which include the North American deserts, Sahel, northern Sahara and Karoo. Generally the two groups were divided into low latitude, summer rainfall regions and higher latitude, winter rainfall ones, although there were some clear anomalies. The findings suggest that comparative studies of biotic responses to rainfall variability between arid Australia (particular southern regions) and other deserts are warranted before paradigms and models based on the uniqueness of Australias arid environment are accepted.

The skin microbiome : impact of modern environments on skin ecology, barrier integrity, and systemic immune programming

Skin barrier structure and function is essential to human health. Hitherto unrecognized functions of epidermal keratinocytes show that the skin plays an important role in adapting whole-body physiology to changing environments, including the capacity to produce a wide variety of hormones, neurotransmitters and cytokine that can potentially influence whole-body states, and quite possibly, even emotions. Skin microbiota play an integral role in the maturation and homeostatic regulation of keratinocytes and host immune networks with systemic implications. As our primary interface with the external environment, the biodiversity of skin habitats is heavily influenced by the biodiversity of the ecosystems in which we reside. Thus, factors which alter the establishment and health of the skin microbiome have the potential to predispose to not only cutaneous disease, but also other inflammatory non-communicable diseases (NCDs). Indeed, disturbances of the stratum corneum have been noted in allergic diseases (eczema and food allergy), psoriasis, rosacea, acne vulgaris and with the skin aging process. The built environment, global biodiversity losses and declining nature relatedness are contributing to erosion of diversity at a micro-ecological level, including our own microbial habitats. This emphasises the importance of ecological perspectives in overcoming the factors that drive dysbiosis and the risk of inflammatory diseases across the life course.

A game of cat-and-mouse: microhabitat influences rodent foraging in recently burnt but not long unburnt shrublands

We investigated the influence of vegetation structure and fire history on the foraging behavior of small rodents (Notomys mitchellii, Pseudomys hermannsburgensis, and Mus musculus) by conducting giving-up density (GUD) experiments in recently burnt (9–13 years since last fire) and long unburnt shrublands (> 40 years), and open and sheltered microhabitats, in a semiarid region of Western Australia. We predicted that rodents would spend less time foraging in recently burnt shrublands and open microhabitat and that the influence of microhabitat would be weaker in long unburnt compared to more recently burnt vegetation. Our findings show that fire history and microhabitat structure influence the foraging behavior of the study species and that the influence of microhabitat varies between fire histories. GUDs were higher in long unburnt vegetation and in open microhabitats. There was a microhabitat effect in recently burnt vegetation, but not in long unburnt. Rodents foraged more in sheltered microhabitats probably because predator encounters are less likely to occur there and it provides them with greater refuge from predation. The presence of a microhabitat effect in recently burnt, but not long unburnt vegetation suggests that understory vegetation density is more important in mediating predation risk than canopy density. Future studies of small mammal responses to land management actions should include behavioral, as well as population-level responses to differing fire regimes.

Species distribution modelling using bioclimatic variables to determine the impacts of a changing climate on the western ringtail possum (Pseudocheirus occidentals; Pseudocheiridae)

The ngwayir (western ringtail possum Pseudocheirus occidentalis ) is an arboreal species endemic to south-western Australia. The range and population of this species have been significantly reduced through multiple anthropogenic impacts. Classified as vulnerable, the ngwayir is highly susceptible to extremes of temperature and reduced water intake. Ngwayir distribution was determined using three different species distribution models using ngwayir presence records related to a set of 19 bioclimatic variables derived from historical climate data, overlaid with 2050 climate change scenarios. MaxEnt was used to identify core habitat and demonstrate how this habitat may be impacted. A supplementary modelling exercise was also conducted to ascertain potential impacts on the tree species that are core habitat for ngwayir. All models predicted a reduction of up to 60% in the range of the ngwayir and its habitat, as a result of global warming towards the south-west of the project area, with a mean potential distribution of 10.3% of the total modelled area of 561 059 km 2 . All three tree species modelled (jarrah, marri and peppermint) were predicted to experience similar contractions in range throughout most of the predicted ngwayir range, although their distributions differed. Populations of ngwayir persisting outside core habitat may indicate potential conservation opportunities.

Response of a shrubland mammal and reptile community to a history of landscape-scale wildfire

Fire plays a strong role in structuring fauna communities and the habitat available to them in fire-prone regions. Human-mediated increases in fire frequency and intensity threaten many animal species and understanding how these species respond to fire history and its associated effect on vegetation is essential to effective biodiversity management. We used a shrubland mammal and reptile community in semiarid south-western Australia as a model to investigate interactions between fire history, habitat structure and fauna habitat use. Of the 15 species analysed, five were most abundant in recently burnt habitat (8–13 years since last fire), four were most abundant in long unburnt areas (25–50 years) and six showed no response to fire history. Fauna responses to fire history were divergent both within and across taxonomic groups. Fire management that homogenises large areas of habitat through either fire exclusion or frequent burning may threaten species due to these diverse requirements, so careful management of fire may be needed to maximise habitat suitability across the landscape. When establishing fire management plans, we recommend that land managers exercise caution in adopting species-specific information from different locations and broad vegetation types. Information on animal responses to fire is best gained through experimental and adaptive management approaches at the local level.

Mapping vegetation in an arid, mountainous region of Western Australia

. Predictive mapping of vegetation using models linking vegetation units to mapped environmental variables has been advocated for remote areas. In this study, three different types of model were employed (within a GIS) to produce vegetation maps of the Hamersley Ranges region of Western Australia. The models were: (1) decision trees; (2) statistical models; and (3) heuristic/conceptual models. Maps were produced for three different levels of a floristic classification, i.e. 16 communities in two community groups with eight subgroups. All models satisfactorily established relationships between the vegetation units and available predictor variables, except where the number of sites of a particular unit was small. The different models often made similar predictions, especially for more widespread vegetation units. Map accuracy (as determined by field testing of maps) improved with increasing level of abstraction, with plant community maps ca. 50 % correct, subgroup maps ca. 60 % correct and group maps 90 % correct. Map inaccuracies were due to several factors, including low sample numbers producing unrepresentative models, poor resolution of and errors in available maps of predictor variables, and available predictor variables not being able to differentiate between certain vegetation units, particularly at the plant community level. Of these factors, poor resolution of maps was seen as the most critical. One type of model could not be recommended over another; however the choice of model will be largely dependent on the nature of the data set and the type of map coverage required.

Fuel dynamics and vegetation recovery after fire in a semiarid Australian shrubland

Understanding fuel dynamics in fire-prone ecosystems is important because fuels play a central role in shaping fire hazard and behaviour. There is ongoing debate over whether fire hazard continually increases with time since fire in shrublands of Mediterranean-type climates, and studies of the temporal changes in fuel loads can contribute to this discussion. We used a chronosequence of fire ages to investigate fuel dynamics and recovery of vegetation structure in the Acacia-dominated shrublands of interior south-west Western Australia. We collected and measured fuels from vegetation with fire ages ranging from 6 to 80+ years and then fitted linear, negative exponential, quadratic and logarithmic models to explore temporal patterns of fuel accumulation. Components of fine ( 50 years). Although there is some evidence of shrub senescence in very long-unburnt vegetation (>60 years), no corresponding decline in fuel levels was detected, suggesting lag effects or inter-fire recruitment to maintain vegetation structure and fuel levels. Fuel structure and quantity varied considerably across the landscape, even within areas of the same landform and time since fire. We found that some of this variation was attributable to soil depth but suggest that other environmental factors may also cause variation in vegetation and fuel characteristics.

Review of climate change adaptation and social protection policies of Ghana: The extent of reducing impacts of climate change and heat stress vulnerability of smallholder farmers

Smallholder farming has become a significant livelihood coping strategy of the population in Ghana. However, in the last decade the upsurge of climate change and the effect of heat stress vulnerability on smallholder farmers in Northern Ghana are alarming. This article investigates the chances of using social protection and climate change adaptation policies towards the management of risks associated with heat stress emanating from climate change. It reviews salient literature on heat stress, social protection, and climate change policies and develops a model upon which both domestic and international interest in climate and social protection policies of Ghana and Sub-Sahara Africa can reduce or aggravate heat stress impacts on smallholder farmers both at their working environment and at household level. It exemplifies the efficacy of the strength of social protection and climate change adaptation policies in Ghana and its impacts on vulnerable rural smallholder farmers and how such situation is replicated in many parts of Africa. It outlines further measures that can be undertaken by governments and international donor agencies to revamp the destitution of smallholder farmers to climate change and heat stress in African region.

Vegetation – environment relationships of the Hamersley Ranges, a mountainous desert of north-west Australia

Understanding environment-vegetation relationships provides important ecological insights, and here we examined such relationships for the Hamersley Ranges of North West Australia. We were particularly interested to see if such relationships were similar to those of other mountainous deserts. We used direct gradient analyses of floristic and environmental variables (constrained ordination), supplemented by identification of environmental differences between plant communities, assessment of environment-vegetation associations and partitioning of the floristic variance between environmental, climatic and spatial variables. Most communities could be differentiated from others according to environmental variables, with slope, surface stone cover, topsoil phosphorus and pH particularly good at differentiating between plant communities. There was strong association between communities and classes of landform and/or geological substrate. Gradient analysis demonstrated the primary floristic gradient was linked to a complex of several topographic, edaphic and geomorphic variables. This was interpreted as floristic change along broad topo-sequences from mountain/ridge tops to valley floors over which gradients in key environmental variables occur. Gradient analyses of other mountainous deserts have reported similar findings. A key distinction in the complex gradient identified for the Hamersley Ranges is the inclusion of topsoil phosphorus (rather than nitrogen) and time since last fire. The second most important floristic gradient was linked to soil pH and conductivity, which reflects floristic variation due to differences in geological substrate throughout the study area.

Incorporating field studies into species distribution and climate change modelling: A case study of the koomal trichosurus vulpecula hypoleucus (phalangeridae)

Species distribution models (SDMs) are an effective way of predicting the potential distribution of species and their response to environmental change. Most SDMs apply presence data to a relatively generic set of predictive variables such as climate. However, this weakens the modelling process by overlooking the responses to more cryptic predictive variables. In this paper we demonstrate a means by which data gathered from an intensive animal trapping study can be used to enhance SDMs by combining field data with bioclimatic modelling techniques to determine the future potential distribution for the koomal (Trichosurus vulpecula hypoleucus). The koomal is a geographically isolated subspecies of the common brushtail possum, endemic to south-western Australia. Since European settlement this taxon has undergone a significant reduction in distribution due to its vulnerability to habitat fragmentation, introduced predators and tree/shrub dieback caused by a virulent group of plant pathogens of the genus Phytophthora. An intensive field study found: 1) the home range for the koomal rarely exceeded 1 km in in length at its widest point; 2) areas heavily infested with dieback were not occupied; 3) gap crossing between patches (>400 m) was common behaviour; 4) koomal presence was linked to the extent of suitable vegetation; and 5) where the needs of koomal were met, populations in fragments were demographically similar to those found in contiguous landscapes. We used this information to resolve a more accurate SDM for the koomal than that created from bioclimatic data alone. Specifically, we refined spatial coverages of remnant vegetation and dieback, to develop a set of variables that we combined with selected bioclimatic variables to construct models. We conclude that the utility value of an SDM can be enhanced and given greater resolution by identifying variables that reflect observed, species-specific responses to landscape parameters and incorporating these responses into the model.