Showing papers by "Stephen E. Williams published in 2015"

Assessing species' vulnerability to climate change

Abstract: The effects of climate change on biodiversity are increasingly well documented, and many methods have been developed to assess species' vulnerability to climatic changes, both ongoing and projected in the coming decades. To minimize global biodiversity losses, conservationists need to identify those species that are likely to be most vulnerable to the impacts of climate change. In this Review, we summarize different currencies used for assessing species' climate change vulnerability. We describe three main approaches used to derive these currencies (correlative, mechanistic and trait-based), and their associated data requirements, spatial and temporal scales of application and modelling methods. We identify strengths and weaknesses of the approaches and highlight the sources of uncertainty inherent in each method that limit projection reliability. Finally, we provide guidance for conservation practitioners in selecting the most appropriate approach(es) for their planning needs and highlight priority areas for further assessments.

Detectability in Audio-Visual Surveys of Tropical Rainforest Birds: The Influence of Species, Weather and Habitat Characteristics.

Abstract: Indices of relative abundance do not control for variation in detectability, which can bias density estimates such that ecological processes are difficult to infer. Distance sampling methods can be used to correct for detectability, but in rainforest, where dense vegetation and diverse assemblages complicate sampling, information is lacking about factors affecting their application. Rare species present an additional challenge, as data may be too sparse to fit detection functions. We present analyses of distance sampling data collected for a diverse tropical rainforest bird assemblage across broad elevational and latitudinal gradients in North Queensland, Australia. Using audio and visual detections, we assessed the influence of various factors on Effective Strip Width (ESW), an intuitively useful parameter, since it can be used to calculate an estimate of density from count data. Body size and species exerted the most important influence on ESW, with larger species detectable over greater distances than smaller species. Secondarily, wet weather and high shrub density decreased ESW for most species. ESW for several species also differed between summer and winter, possibly due to seasonal differences in calling behavior. Distance sampling proved logistically intensive in these environments, but large differences in ESW between species confirmed the need to correct for detection probability to obtain accurate density estimates. Our results suggest an evidence-based approach to controlling for factors influencing detectability, and avenues for further work including modeling detectability as a function of species characteristics such as body size and call characteristics. Such models may be useful in developing a calibration for non-distance sampling data and for estimating detectability of rare species.

Climate change and the impacts of extreme events on Australia's Wet Tropics biodiversity

Abstract: [Extract] This project proposes to provide information and tools to enable scientists and management agencies to predict and limit the impacts of extreme climatic events on Australia's biodiversity. It aims to determine the exposure, sensitivity and vulnerability of Wet Tropics biodiversity to climatic extremes, and assess contemporary and future impacts. Landscape-scale exposure will be mapped by determining relationships between broad-scale macro climate and direct measurements of organism exposure in different environments. Microhabitat-scale exposure will be determined by combining the microhabitat preferences of Wet Tropics biota with the thermal characteristics of their known preferred habitat. Landscape-scale and microhabitat-scale exposure will be combined to map accurately temperatures experienced by organisms in-situ. Sensitivity of Wet Tropics biota to temperature extremes will be determined by integrating information on their thermal tolerance limits, their resilience, and their capacity to adapt. Thermal tolerance limits have already been quantified by the James Cook University researchers for a range of representative taxa. Using validated methodology, data on thermal physiology of an additional 25 key taxa will be collected in-situ. Resilience will be quantified from known traits that affect a species’ ability to survive and recover from an environmental insult. The capacity to adapt will be estimated by comparing the thermal characteristics of a species’ most favourable microhabitat with that of its other viable habitats. The three types of information will then be combined to obtain highly accurate estimates for the sensitivities of a range of representative Wet Tropics species. The project will explicitly incorporate the correlative and, where possible, mechanistic links between exposure and sensitivity to model spatiotemporal variation in current and future vulnerability to extreme temperature events. This will enable the mapping of impacts of anthropogenic changes in the regimes of temperature extremes on the distribution, abundance and extinction risk of species, something that has not been attempted before in any region. The project will initially concentrate on the regimes of temperature extremes; however, analytical approaches will then also be applied to the regimes of other extreme climatic events, particularly droughts and wildfires as they are strongly linked to extreme heat events. The ultimate aim is to develop a generalised framework for assessing the vulnerability of any natural system to any extreme climatic event. This will be critical for informing proactive conservation strategies that minimise biotic vulnerability to such events in the face of climate change. Project outputs at a glance Accurate high resolution maps of the exposure to temperature extremes as experienced by organisms in-situ. Accurate estimates of the sensitivities of organisms to temperature extremes. Identification of the areas where biodiversity is currently most vulnerable to temperature extremes ('thermal hotspots'). Identification of the areas where biodiversity is least vulnerable to temperatures extremes in the future ('thermal refugia'). A list of biodiversity values particularly at risk from extreme events. A generalised analytical toolkit for assessing vulnerability to extreme climatic events in Australia and elsewhere. Specific objectives and intended outputs of this Project are detailed in the NERP TE Hub Multi-Year Research Plan.