Kelaher B.P.,Southern Cross University of Australia |
Bishop M.J.,Macquarie University |
Potts J.,NSW Office of Environment and Heritage |
Scanes P.,NSW Office of Environment and Heritage |
Skilbeck G.,University of Technology, Sydney
Global Change Biology | Year: 2013
Global losses of seagrasses and mangroves, eutrophication-driven increases in ephemeral algae, and macrophyte invasions have impacted estuarine detrital resources. To understand the implications of these changes on benthic ecosystem processes, we tested the hypotheses that detrital source richness, mix identity, and biomass influence benthic primary production, metabolism, and nutrient fluxes. On an estuarine muddy sandflat, we manipulated the availability of eight detrital sources, including mangrove, seagrass, and invasive and native algal species that have undergone substantial changes in distribution. Mixes of these detrital sources were randomly assigned to one of 12 treatments and dried detrital material was added to seventy-two 0.25 m2 plots (n = 6 plots). The treatments included combinations of either two or four detrital sources and high (60 g) or low (40 g) levels of enrichments. After 2 months, the dark, light, and net uptake of NH4 +, dissolved inorganic nitrogen, and the dark efflux of dissolved organic nitrogen were each significantly influenced by the identity of detrital mixes, rather than detrital source richness or biomass. However, gross and net primary productivity, average oxygen flux, and net NOX and dissolved inorganic phosphorous fluxes were significantly greater in treatments with low than with high detrital source richness. These results demonstrate that changes in detrital source richness and mix identity may be important drivers of estuarine ecosystem performance. Continued impacts to estuarine macrophytes may, therefore, further alter detritus-fueled productivity and processes in estuaries. Specific tests that address predicted future changes to detrital resources are required to determine the consequences of this significant environmental problem. © 2013 Blackwell Publishing Ltd.
Fordham D.A.,University of Adelaide |
Akcakaya H.R.,State University of New York at Stony Brook |
Araujo M.B.,CSIC - National Museum of Natural Sciences |
Araujo M.B.,University of Évora |
And 4 more authors.
Ecography | Year: 2013
Ecological niche models (ENMs) are the primary tool used to describe and forecast the potential influence of climate change on biodiversity. However, ENMs do not directly account for important biological and landscape processes likely to affect range dynamics at a variety of spatial scales. Recent advances to link ENMs with population models have focused on the fundamental step of integrating dispersal and metapopulation dynamics into forecasts of species geographic ranges. Here we use a combination of novel analyses and a synthesis of findings from published plant and animal case studies to highlight three seldom recognised, yet important, advantages of linking ENMs with demographic modelling approaches: 1) they provide direct measures of extinction risk in addition to measures of vulnerability based on change in the potential range area or total habitat suitability. 2) They capture life-history traits that permit population density to vary in different ways in response to key spatial drivers, conditioned by the processes of global change. 3) They can be used to explore and rank the cost effectiveness of regional conservation alternatives and demographically oriented management interventions. Given these advantages, we argue that coupled methods should be used preferentially where data permits and when conservation management decisions require intervention, prioritization, or direct estimates of extinction risk. © 2013 The Author. Ecography © 2013 Nordic Society Oikos.
Saintilan N.,NSW Office of Environment and Heritage |
Rogers K.,University of Wollongong |
Mazumder D.,Australian Nuclear Science and Technology Organization |
Woodroffe C.,University of Wollongong
Estuarine, Coastal and Shelf Science | Year: 2013
Estimates of carbon store and carbon accumulation rate in mangrove and saltmarsh are beset by issues of scale and provenance. Estimates at a site do not allow scaling to regional estimates if the drivers of variability are not known. Also, carbon accumulation within soils provides a net offset only if carbon is derived in-situ, or would not otherwise be sequestered. We use a network of observation sites extending across 2000km of southeastern Australian coastline to determine the influence of geomorphic setting and coastal wetland vegetation type on rates of carbon accumulation, carbon store and probable sources. Carbon accumulation above feldspar marker horizons over a 10-year period was driven primarily by tidal range and position in the tidal frame, and was higher for mangrove and saltmarsh dominated by Juncus kraussii than for other saltmarsh communities. The rate of carbon loss with depth varied between geomorphic settings and was the primary determinant of carbon store. A down-core enrichment in δ13C was consistent with an increased relative contribution of mangrove root material to soil carbon, as mangrove roots were found to be consistently enriched compared to leaves. We conclude that while surface carbon accumulation is driven primarily by tidal transport of allocthonous sediment, in-situ carbon sequestration is the dominant source of recalcitrant carbon, and that mangrove and saltmarsh carbon accumulation and store is high in temperate settings, particularly in mesotidal and fluvial geomorphic settings. © 2013 Elsevier Ltd.
Luo Q.,University of Technology, Sydney |
Wen L.,NSW Office of Environment and Heritage |
McGregor J.L.,CSIRO |
Timbal B.,Center for Australian Weather and Climate Research
Climatic Change | Year: 2013
This study aims to evaluate the performance of two mainstream downscaling techniques: statistical and dynamical downscaling and to compare the differences in their projection of future climate change and the resultant impact on wheat crop yields for three locations across New South Wales, Australia. Bureau of Meteorology statistically- and CSIRO dynamically-downscaled climate, derived or driven by the CSIRO Mk 3.5 coupled general circulation model, were firstly evaluated against observed climate data for the period 1980-1999. Future climate projections derived from the two downscaling approaches for the period centred on 2055 were then compared. A stochastic weather generator, LARS-WG, was used in this study to derive monthly climate changes and to construct climate change scenarios. The Agricultural Production System sIMulator-Wheat model was then combined with the constructed climate change scenarios to quantify the impact of climate change on wheat grain yield. Statistical results show that (1) in terms of reproducing the past climate, statistical downscaling performed better over dynamical downscaling in most of the cases including climate variables, their mean, variance and distribution, and study locations, (2) there is significant difference between the two downscaling techniques in projected future climate change except the mean value of rainfall across the three locations for most of the months; and (3) there is significant difference in projected wheat grain yields between the two downscaling techniques at two of the three locations. © 2013 Springer Science+Business Media Dordrecht.
Scheele B.C.,Australian National University |
Guarino F.,University of Canberra |
Osborne W.,University of Canberra |
Hunter D.A.,NSW Office of Environment and Heritage |
And 2 more authors.
Biological Conservation | Year: 2014
The disease chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), is a key driver of global amphibian declines. While chytridiomycosis can cause extinction, many susceptible species persist after an initial period of decline, albeit with reduced abundance and distribution. Emerging evidence indicates that amphibian abundance can recover within remnant populations, but to date, the capacity of amphibian populations to re-expand into historically occupied habitat has received limited research attention. We surveyed 145 sites in 2011 and 2012 to determine if populations of the whistling tree frog (Litoria verreauxii verreauxii) have re-expanded compared with historical data from 1975-1976, 1990 and 1996. L. v. verreauxii underwent a major range contraction likely caused by chytridiomycosis between the first two time periods. Populations have recently re-expanded, with 39 new sites colonised despite high prevalence of Bd. We suspect that changes in disease dynamics have resulted in the increased coexistence of L. v. verreauxii and Bd. Habitat attributes at sites that retained frogs for the duration of the study indicate that high quality habitat may contribute to buffering against population level effects of Bd. Colonised sites had more coarse woody debris, suggesting a possible habitat management strategy to encourage range expansion for this species. Given sufficient time and adequate source populations in high quality habitat, it is possible that other amphibian species may re-expand from chytridiomycosis-induced declines. This provides an impetus for the protection of historical, but currently unoccupied amphibian habitats and highlights the importance of maintaining high quality habitat to help species survive novel shocks such as pandemic diseases. © 2013 Elsevier Ltd.
Ji F.,NSW Office of Environment and Heritage |
Ekstrom M.,CSIRO |
Evans J.P.,University of New South Wales |
Theoretical and Applied Climatology | Year: 2014
This study evaluated the ability of Weather Research and Forecasting (WRF) multi-physics ensembles to simulate storm systems known as East Coast Lows (ECLs). ECLs are intense low-pressure systems that develop off the eastern coast of Australia. These systems can cause significant damage to the region. On the other hand, the systems are also beneficial as they generate the majority of high inflow to coastal reservoirs. It is the common interest of both hazard control and water management to correctly capture the ECL features in modeling, in particular, to reproduce the observed spatial rainfall patterns. We simulated eight ECL events using WRF with 36 model configurations, each comprising physics scheme combinations of two planetary boundary layer (pbl), two cumulus (cu), three microphysics (mp), and three radiation (ra) schemes. The performance of each physics scheme combination and the ensembles of multiple physics scheme combinations were evaluated separately. Results show that using the ensemble average gives higher skill than the median performer within the ensemble. More importantly, choosing a composite average of the better performing pbl and cu schemes can substantially improve the representation of high rainfall both spatially and quantitatively. © 2013 Springer-Verlag Wien.
James E.A.,Royal Botanic Gardens Melbourne |
James E.A.,University of Melbourne |
McDougall K.L.,NSW Office of Environment and Heritage |
McDougall K.L.,La Trobe University
Annals of Botany | Year: 2014
Background and Aims The association of clonality, polyploidy and reduced fecundity has been identified as an extinction risk for clonal plants. Compromised sexual reproduction limits both their ability to adapt to new conditions and their capacity to disperse to more favourable environments. Grevillea renwickiana is a prostrate, putatively sterile shrub reliant on asexual reproduction. Dispersal is most likely limited by the rate of clonal expansion via rhizomes. The nine localized populations constituting this species provide an opportunity to examine the extent of clonality and spatial genotypic diversity to evaluate its evolutionary prospects. Methods Ten microsatellite loci were used to compare genetic and genotypic diversity across all sites with more intensive sampling at four locations (n = 185). The spatial distribution of genotypes and chloroplast DNA haplotypes based on the trnQ-rps16 intergenic spacer region were compared. Chromosome counts provided a basis for examining genetic profiles inconsistent with diploidy. Key Results Microsatellite analysis identified 46 multilocus genotypes (MLGs) in eight multilocus clonal lineages (MLLs). MLLs are not shared among sites, with two exceptions. Spatial autocorrelation was significant to 1·6 km. Genotypic richness ranged from 0 to 0·33. Somatic mutation is likely to contribute to minor variation between MLGs within clonal lineages. The eight chloroplast haplotypes identified were correlated with eight MLLs defined by ordination and generally restricted to single populations. Triploidy is the most likely reason for tri-allelic patterns. Conclusions Grevillea renwickiana comprises few genetic individuals. Sterility has most likely been induced by triploidy. Extensive lateral suckering in long-lived sterile clones facilitates the accumulation of somatic mutations, which contribute to the measured genetic diversity. Genetic conservation value may not be a function of population size. Despite facing evolutionary stagnation, sterile clonal species can play a vital role in mitigating ecological instability as floras respond to rapid environmental change. © 2014 The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: firstname.lastname@example.org.
You Z.-J.,NSW Office of Environment and Heritage
Coasts and Ports 2013 | Year: 2013
A unified model is presented to estimate critical coastal water depths from three distinct modes of sediment transport: initiation of sediment motion (bedload only), inception of ripple formation (bed and suspended loads), and inception of ripple disappearance (bed load mainly) on a horizontal bed of sediment under regular waves based on the laboratory data. The critical depths are then derived from this unified criterion according to linear wave theory. It is found that the critical depths are the function of sediment grain size and density and wave height and period, but much more affected by wave period than sand grain size. The critical depth estimated from inception of sediment ripple formation is found to be much larger than the depth of closure (DOC) that is commonly defined for beach-fill designs.
Auld T.D.,NSW Office of Environment and Heritage |
Auld T.D.,University of New South Wales |
Leishman M.R.,Macquarie University
Austral Ecology | Year: 2015
Gnarled Mossy Cloud Forest is a globally unique ecosystem, combining floristic elements from Australia, New Zealand and New Caledonia. It is restricted to a very small area (28ha) at elevations above 750m on the summits of two mountains on Lord Howe Island in the Pacific Ocean, approximately 570km off the east coast of Australia. Moisture derived from clouds is a key feature of the ecosystem. We assessed the conservation status of this ecosystem using the International Union for the Conservation of Nature Red List criteria for ecosystems. There has been no historical clearing of the ecosystem, but declines (with large uncertainty bounds) were estimated for two abiotic variables that are important in maintaining the component species (cloud cover and rainfall). Overall, we found the ecosystem to be Critically Endangered based on a restricted geographic distribution combined with continuing decline (criterion B1aii, iii, B1b, B1c and B2aii, iii, B2b, B2c). Decline was inferred from: a loss of moisture from declining rainfall and cloud cover due to climate change (affecting disturbance regimes, gap formation and species survival and recruitment); ongoing exotic rat predation on seeds and seedlings of several sensitive species that are structural components of the ecosystem (affecting survival and recruitment); and the fact that the ecosystem is considered to exist at only one location. This mirrors similar threats from exotic species and climate change to other Pacific island cloud forests. Eradication of rats from Lord Howe Island will reduce the immediate risk to this ecosystem; however, only global mitigation of greenhouse gases could alleviate risk from declining cloud cover and moisture availability. © 2014 Ecological Society of Australia.
Tozer M.G.,NSW Office of Environment and Heritage |
Leishman M.R.,Macquarie University |
Auld T.D.,NSW Office of Environment and Heritage
Austral Ecology | Year: 2015
The International Union for the Conservation of Nature (IUCN) has proposed a standard global assessment protocol for the evaluation of conservation risks to ecosystems. The assessment criteria mirror the IUCN protocol for the assessment of species, however there are relatively few case studies available to demonstrate their utility across a broad range of ecosystems. We applied the IUCN protocol to assess the conservation status of the Cumberland Plain Woodland (CPW) located in the western suburbs of Sydney, Australia. The ecosystem has been the focus of extensive survey and research and has been determined to be critically endangered under NSW and Australian Government legislation, primarily as a consequence of its history of extensive clearing. The outcome of the risk assessment for CPW using the IUCN protocol was identical to those under the NSW and Australian legislation. Data for risk assessment fell into two categories, each with different limitations. Phytosocialogical data and distribution models provided a strong basis for quantifying past and future changes in the distribution of CPW, but offered only indirect measures of functional symptoms of decline. Conversely, local case studies documenting declines in ecosystem function due to weed invasion, soil disturbance and alteration of fire regimes could not easily be extrapolated in order to evaluate the assessment criteria. The critically endangered rating was based solely on the historic reduction in geographic distribution (92-94%), however clearing poses an ongoing threat to the ecosystem. The contemporary clearing rate of CPW is approximately half the historical average but there is evidence that the rate will double in the next decade as a consequence of ongoing urbanisation and Government policy of biodiversity offsets. A systematic approach to documenting the extent of environmental degradation and disruption to biotic processes would assist the assessment of CPW and other ecosystems against the IUCN criteria. © 2014 Ecological Society of Australia.