Australian Ecosystems Research Articles

Detecting regime shifts in marine systems with limited biological data: An example from southeast Australia

The ability to detect ecological regime shifts in a data-limited setting was investigated, using southeast Australian ecosystems as a model. Community variability was summarized for 1968–2008 with the first two principal components (PCs) of recruitment estimates for six fish stocks and reproductive parameters for four seabird species; regional climate was summarized for 1953–2008 with the first two PCs for three parameters (sea surface temperature [SST], sea surface salinity, surface nitrate) measured at two stations; and basin-scale climate variability was summarized for 1950–2012 with mean South Pacific SST and the first two PCs of detrended South Pacific SST. The first two biology PCs explained 45% of total community variability. The first two PCs of basin-scale SST showed abrupt shifts similar to “regime” behavior observed in other ocean basins, and the first PC of basin-scale SST showed significant covariation with the first PC of regional climate. Together, these results are consistent with the strong community variability and decadal-scale red noise climatic variability associated with Northern Hemisphere regime shifts. However, statistical model selection showed that the first two PCs of regional climate and the first PC of biology time series all exhibited linear change, rather than abrupt shifts. This result is consistent with previous studies documenting rapid linear change in the climate and biology of southeast Australian shelf ecosystems, and we conclude that there is no evidence for regime shift behavior in the region’s ecology. However, analysis of a large set of previously-published biological time series from the North Pacific (n=64) suggests that studies using fewer than ∼30 biological time series, such as this one, may be unable to detect regime shifts. Thus we conclude that the nature of ecological variability in the region cannot be determined with available data. The development of additional long-term biological observations is needed for understanding change in southeast Australia and in many other marine ecosystems globally.

Quantifying the prediction accuracy of a 1-D SVAT model at a range of ecosystems in the USA and Australia: evidence towards its use as a tool to study Earth's system interactions

Abstract. This paper describes the validation of the SimSphere SVAT (Soil–Vegetation–Atmosphere Transfer) model conducted at a range of US and Australian ecosystem types. Specific focus was given to examining the models' ability in predicting shortwave incoming solar radiation (Rg), net radiation (Rnet), latent heat (LE), sensible heat (H), air temperature at 1.3 m (Tair 1.3 m) and air temperature at 50 m (Tair 50 m). Model predictions were compared against corresponding in situ measurements acquired for a total of 72 selected days of the year 2011 obtained from eight sites belonging to the AmeriFlux (USA) and OzFlux (Australia) monitoring networks. Selected sites were representative of a variety of environmental, biome and climatic conditions, to allow for the inclusion of contrasting conditions in the model evaluation. Overall, results showed a good agreement between the model predictions and the in situ measurements, particularly so for the Rg, Rnet, Tair 1.3 m and Tair 50 m parameters. The simulated Rg parameter exhibited a root mean square deviation (RMSD) within 25 % of the observed fluxes for 58 of the 72 selected days, whereas an RMSD within ~ 24 % of the observed fluxes was reported for the Rnet parameter for all days of study (RMSD = 58.69 W m−2). A systematic underestimation of Rg and Rnet (mean bias error (MBE) = −19.48 and −16.46 W m−2) was also found. Simulations for the Tair 1.3 m and Tair 50 m showed good agreement with the in situ observations, exhibiting RMSDs of 3.23 and 3.77 °C (within ~ 15 and ~ 18 % of the observed) for all days of analysis, respectively. Comparable, yet slightly less satisfactory simulation accuracies were exhibited for the H and LE parameters (RMSDs = 38.47 and 55.06 W m−2, ~ 34 and ~ 28 % of the observed). Highest simulation accuracies were obtained for the open woodland savannah and mulga woodland sites for most of the compared parameters. The Nash–Sutcliffe efficiency index for all parameters ranges from 0.720 to 0.998, suggesting a very good model representation of the observations. To our knowledge, this study presents the most detailed evaluation of SimSphere done so far, and the first validation of it conducted in Australian ecosystem types. Findings are important and timely, given the expanding use of the model both as an educational and research tool today. This includes ongoing research by different space agencies examining its synergistic use with Earth observation data towards the development of global operational products.

A test of the feasibility of using glue traps to sample the invertebrate fauna in bilby Macrotis lagotis foraging pits

Interactions between mammals and invertebrates remain a gap in our knowledge of the role of fossorial foragers in Australian ecosystems. This is probably because digging mammals disappeared from the majority of their former range before they could be studied and because of the difficulties associated with sampling invertebrates in foraging pits. Bilbies were reintroduced into a rangeland restoration program in Western Australia, providing an opportunity to compare invertebrates in their foraging pits with the undisturbed surface soil. The challenge was to develop a method for collecting invertebrates while minimising disturbance of the floor of the foraging pits. This study investigated the feasibility of using folding cardboard glue traps to sample the invertebrates. The traps proved to be easy to deploy and collect and concerns that the traps on the soil surface would collect more soil than those in the foraging pits, thereby biasing the invertebrate sample, were not realised. No firm conclusions can be...

Microsatellite analysis indicates that Puccinia psidii in Australia is mutating but not recombining

Puccinia psidii is considered a biosecurity threat in Australia because of its broad host range that includes many species of Myrtaceae which dominate Australian ecosystems. Since it was first reported in this country, in April 2010, there has been little information about the population structure of the pathogen. In this study, six microsatellite loci were analysed to determine the genetic relationship among rust specimens from different hosts and locations in Australia, New Caledonia, Hawaii and China. The Chinese and New Caledonian specimens share a multi-locus genotype with the majority of the Australian specimens. The results also indicated a close relationship between Australian and Hawaiian samples. At present, the P. psidii population in Australia is genetically uniform with no evidence of sexual recombination. Five of the 104 collections varied by one allele at single loci, indicating that mutations are common but persistence of the mutants in the population may be less common.

Assessing and managing risks to ecosystem biodiversity

AbstractEcosystem conservation is important for biodiversity and for human well‐being. Understanding the relative risks to ecosystems is fundamental to well‐informed ecosystem management. The IUCN Red List of Ecosystems protocol provides an adaptable framework for risk assessment across terrestrial, subterranean, freshwater and marine ecosystems. I review a series of detailed case studies, published in this special edition of Austral Ecology, that apply the Red List of Ecosystems criteria to a broad range of ecosystem types. These studies show that detailed risk assessments are especially valuable as forerunners to strategic ecosystem management. Key components of Red List assessments that contribute to development of management strategies include critical diagnosis of trends and their causes, identification of dependencies that influence ecosystem responses to environmental change and selection of ecosystem‐specific diagnostic variables that can be useful monitoring tools for evaluating the performance of management. Ecosystem Red List assessments are crucial to regulatory processes under environmental legislation in Australia and other countries. The IUCN Red List of Ecosystem criteria will help improve the scientific rigour of statutory listings and could also provide a unifying framework for the suite of listing processes that differ among jurisdictions for historical reasons. When integrated with a comprehensive ecosystem typology, ecosystem Red List assessments can also provide critical input into systematic conservation planning. The case studies demonstrate a range of analytical approaches to risk assessment framed to accommodate data of varying quality and abundance. I conclude by exploring opportunities and requirements for a systematic continental‐scale Red List assessment of Australian ecosystems.

Two Weeds Unwilded

Research Article| May 01 2015 Two Weeds Unwilded Tom Celebrezze Tom Celebrezze Ever since reading about Tasmanian devils at the public library in Olmsted Falls, Ohio, Tom Celebrezze was destined for a life Down Under. He studied at Stanford and University of Wisconsin–Madison before heading to the antipodes to take up a Rotary International “Preserve Planet Earth” Scholarship in Adelaide. His doctorate was on the genetic and population effects of honeybees on Australian ecosystems (University of Wollongong). He now lives with his Aussie partner in Sydney, managing government conservation programs. He is on Pinterest. Search for other works by this author on: This Site PubMed Google Scholar Gastronomica (2015) 15 (2): 74–79. https://doi.org/10.1525/gfc.2015.15.2.74 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Cite Icon Cite Search Site Citation Tom Celebrezze; Two Weeds Unwilded. Gastronomica 1 May 2015; 15 (2): 74–79. doi: https://doi.org/10.1525/gfc.2015.15.2.74 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentGastronomica Search This content is only available via PDF. © 2015 by The Regents of the University of California2015 Article PDF first page preview Close Modal You do not currently have access to this content.

A synthesis of postfire recovery traits of woody plants in Australian ecosystems

Postfire resprouting and recruitment from seed are key plant life-history traits that influence population dynamics, community composition and ecosystem function. Species can have one or both of these mechanisms. They confer resilience, which may determine community composition through differential species persistence after fire. To predict ecosystem level responses to changes in climate and fire conditions, we examined the proportions of these plant fire-adaptive traits among woody growth forms of 2880 taxa, in eight fire-prone ecosystems comprising ~87% of Australia's land area. Shrubs comprised 64% of the taxa. More tree (>84%) than shrub (~50%) taxa resprouted. Basal, epicormic and apical resprouting occurred in 71%, 22% and 3% of the taxa, respectively. Most rainforest taxa (91%) were basal resprouters. Many trees (59%) in frequently-burnt eucalypt forest and savanna resprouted epicormically. Although crown fire killed many mallee (62%) and heathland (48%) taxa, fire-cued seeding was common in these systems. Postfire seeding was uncommon in rainforest and in arid Acacia communities that burnt infrequently at low intensity. Resprouting was positively associated with ecosystem productivity, but resprouting type (e.g. basal or epicormic) was associated with local scale fire activity, especially fire frequency. Although rainforest trees can resprout they cannot recruit after intense fires and may decline under future fires. Semi-arid Acacia communities would be susceptible to increasing fire frequencies because they contain few postfire seeders. Ecosystems dominated by obligate seeders (mallee, heath) are also susceptible because predicted shorter inter-fire intervals will prevent seed bank accumulation. Savanna may be resilient to future fires because of the adaptive advantage of epicormic resprouting among the eucalypts. The substantial non-resprouting shrub component of shrublands may decline, but resilient Eucalyptus spp. will continue to dominate under future fire regimes. These patterns of resprouting and postfire seeding provide new insights to ecosystem assembly, resilience and vulnerability to changing fire regimes on this fire-prone continent.

Effects of reconstruction of a pre-European vertebrate assemblage on ground-dwelling arachnids in arid Australia.

Species loss can result in changes in assemblage structure and ecosystem function through ecological cascades. Australian vertebrate assemblages changed significantly following European colonisation, which resulted in the establishment of invasive vertebrates and the loss of native marsupials, many of which consume invertebrates. Conservation focusses on the removal of invasive carnivores and the reintroduction of regionally extinct species to fenced sites, resulting in what could be considered a reconstruction of pre-European vertebrate assemblages. In semi-arid Australian spinifex mallee ecosystems, we asked: (1) what is the effect of reconstructed pre-European vertebrate assemblages on native arachnid assemblages? and (2) what direct or indirect mechanisms (predation, disturbance and/or competition) could plausibly be responsible for these effects? We compared sites with reconstructed vertebrate assemblages with paired control sites. Arachnids were sampled using pitfall trapping and direct searching. Hypotheses regarding mechanisms were tested using scat analysis (predation) and by comparing burrow depth (disturbance) and scorpion mass (competition) between control and reconstructed sites. The dominant dune scorpion, Urodacus yaschenkoi, was less abundant and a wolf spider (Lycosa gibsoni species group) more abundant in reconstructed sites. Differences in spider assemblage composition were marginally non-significant. Scat analysis confirmed native vertebrate predation on scorpions and we found no evidence that competition or disturbance affected scorpions. We, thus, suggest that changes in spider assemblages may have resulted from ecological cascades via decreases in dune scorpions. The loss of omnivorous mammals and other changes associated with the invasion of carnivores may, therefore, have had broad-reaching consequences for native arachnid assemblages in Australian ecosystems.

Winter diet of introduced red deer (Cervus elaphus) in woodland vegetation in Grampians National Park, western Victoria

Although red deer (Cervus elaphus) have the potential to play a major role in influencing the structure and composition of vegetation, little is known about the dietary preferences of red deer in Australia. In the Grampians National Park, Victoria, where there is a large, established red deer population, there has been concern over the condition of woodlands, with lack of perennial seedling recruitment observed. We estimated the diets of 12 red deer using macroscopic sorting techniques. We examined rumen contents of seven male and five female red deer from four woodland Ecological Vegetation Classes, which indicate that they act as intermediate feeders. A wide variety of plants were ingested, with evergreen tree species, small trees and woody shrubs making up a large proportion of the diet, along with grasses. This study found that red deer show significantly different dietary intake due to sex, with females consuming a diet much higher in grasses, while males consume more trees and shrubs. These findings have implications for the management of red deer populations within the park and broader implications for their effects on Australian ecosystems.

The genetic basis of foliar terpene yield: Implications for breeding and profitability of Australian essential oil crops

The family Myrtaceae is known for its high foliar terpene concentrations as well as significant qualitative and quantitative variation in foliar terpenes between taxa, populations and individuals. To date, few studies have investigated the genetic and biochemical processes, which underlie this variation, much of which is known to be under genetic control. Differences in yield are both ecologically and commercially important and a better understanding of its basis will allow a greater understanding of Australian ecosystems as well as improve commercial viability of essential oil industries. Over the past decade a good understanding of the genes involved in terpene biosynthesis has developed in other species and several important regulatory steps have been identified. Much of this work has been done in transgenic plants, so our understanding at a molecular level is strong. Nonetheless, it remains unclear if these processes are transferrable to wild populations, or indeed how ecologically important quantitative variation in terpenoids arise and are maintained in natural ecosystems. In this review we will summarize what is known about terpene biosynthesis and the control of flux through the terpene biosynthetic pathways. We will then argue that this platform of work provides a great resource for Myrtaceae, as well as other plants, to identify candidate genes that control flux through the biosynthetic pathways and how this will inform further studies into the ecological implications of quantitative variation of terpenes. Work into terpene biosynthesis would also provide a framework to improve the profitability of essential oil crops.

Effects of fire on vegetation and arthropods in a coastal heath, south‐east Queensland

SummaryFire is an important part of many Australian ecosystems, and determining how it affects different vegetation communities and associated fauna is of particular interest to land managers. Here, we report on a study that used sites established during a 39‐year fire experiment in coastal heathland in southeastern Queensland to compare arthropod abundance and vegetation in 1.5–2.6 ha sites that were (i) long unburnt, (ii) burnt every 5 years and (iii) burnt every 3 years. We found that the abundance of ants was more than four times higher in the frequently burnt sites compared to long unburnt sits. Moreover, long unburnt sites had greater dominance of Xanthorrhoea johnsonii and Caustis recurvata, whereas burnt sites had greater cover of Lomandra filiformis, Leucopogon margarodes and Leucopogon leptospermoides. Our findings show that frequent fire can alter vegetation structure and composition, and this is matched by an increase in the relative dominance of ants in the arthropod community.

Management of Biodiversity in Australia

The concept of holistic ecosystem research, termed community-physiology, has gradually developed over the last 150 years. The discipline of community-physiology investigates the physico-chemical processes that determine the structure, growth and biodiversity of plant communities (with associated consumers and decomposers), both above and below ground, in space and time, from the tropical north to the temperate south of Australia. These physico-chemical processes (aerodynamic fluxes — frictional, thermal, evaporative ± atmospheric salinity — plus available soil water and soil nutrients) need to be clearly enunciated and integrated in ‘ecosystem models’ in order to predict the effect of perturbations (such as Global Warming, nutrient pollution, invasive biota, fire, overgrazing, etc.) on Australian ecosystems. An increase in global temperatures of 2 o C is predicted to affect the development of the foliage covers of overstorey and understorey strata resulting in open-forests —> woodlands —> open-woodlands —> tall shrublands —> low shrublands throughout Australia. In order to conserve Australian biota for posterity, community-physiologists, ecosystem modelers and environmental impact ecologists must have a deep understanding of the eco-physiology of producers, consumers and decomposers that compose an ecosystem and how these organisms interact with the continually-changing physico-chemical processes in the atmosphere and soil, in space and time.

Intrinsic climate dependency of ecosystem light and water-use-efficiencies across Australian biomes

The sensitivity of ecosystem gross primary production (GPP) to availability of water and photosynthetically active radiation (PAR) differs among biomes. Here we investigated variations of ecosystem light-use-efficiency (eLUE: GPP/PAR) and water-use-efficiency (eWUE: GPP/evapotranspiration) among seven Australian eddy covariance sites with differing annual precipitation, species composition and temperature. Changes to both eLUE and eWUE were primarily correlated with atmospheric vapor pressure deficit (VPD) at multiple temporal scales across biomes, with minor additional correlations observed with soil moisture and temperature. The effects of leaf area index on eLUE and eWUE were also relatively weak compared to VPD, indicating an intrinsic dependency of eLUE and eWUE on climate. Additionally, eLUE and eWUE were statistically different for biomes between summer and winter, except eWUE for savannas and the grassland. These findings will improve our understanding of how light- and water-use traits in Australian ecosystems may respond to climate change.

Ecology of Australian Temperate Reefs

book reviews ISSN 1948-6596 Ecology of Australian Temperate Reefs Ecology of Australian Temperate Reefs: The Unique South. Scoresby Shepherd & Graham Edgar (editors), 2013, CSIRO Publishing. 520 pp. AU$130.00 (hardback) ISBN: 9781486300099; http://www.publish.csiro.au/ This book is a lavishly-produced text that links geological history, oceanography, and biogeogra- phy with future threats to Australian temperate marine ecosystems and their biodiversity. The Preface claims that the book is directed at three audiences. One, marine ecologists who want to broaden their background knowledge; the book certainly would be useful in this regard. Two, un- der- or post-graduate students; the book would be a useful main or supplemental text for a course. Three, as a reference work for “skilled amateur divers and underwater photographers (page xi)”; I disagree, as it's perhaps a bit too de- tailed for the most part, despite what may have been a Publisher’s imperative to sell copies. There are five main parts to the book. A pot- ted summary of the geology, oceanography and biogeographic history of the Southern Ocean. The ecologies of each of the three main taxa: the algae, the invertebrates, and the vertebrates. The last sec- tion covers ecosystems and their conservation. Part One, the backdrop to modern biodiver- sity, was very informative and unusual in a text on marine ecology, providing (in the book’s Table 1.1) a useful summary of the events from 100 Mya to the present, in terms of climatic, tectonic, oceano- graphic and biotic events. Given the current con- cerns about ocean acidification, the section on carbon dioxide in a historic context was very use- ful in terms of past impacts. The rapid summaries of marine taxa in terms of their evolution and his- toric constraints quickly gets the reader up to speed, and includes all key fossil taxa that remain today. Table 3.2 lists the main marine taxa, with information on species diversity, endemism and dispersal potential. However, boundaries of the area of endemism are not stated, and whether they are the same for each taxon is unclear, which would be important to know since endemism is related to habitat area. Also, some of the calcula- tions appear to be in error. For instance, the per- centage of global species richness in temperate Australia for molluscs is given as ca. 8% of 96,850 species, but this should be 20% (19,000 Southern Australian species). And 71 of 1250 species of pycnogonids is 6% not 11%. Evolution and radia- tion of taxa are examined in some detail for many well known—for instance Haliotis abalones and cowries—and less well known taxa—such as the odacine marine fishes. Despite the preface claiming that modeling is not a focus of the volume, Part One ends with several pages comparing the expectations of two key models of southern biodiversity. This may be too much for lay readers but I feel rounds off the section nicely. Parts Two to Four address higher taxa, in turn algae, invertebrates and vertebrates. In Part Two, the algae chapters, case studies fol- low two key habitat formers, Ecklonia radiata and the giant kelp Macrocystis pyrifera. Each case study considers morphology and growth forms, then demographic parameters and their spatial variation. Table 4.1 is a very useful com- parison of growth, biomass and survival charac- teristics around southern Australia for the ubiquitous Ecklonia radiata. The relationship between depth and biomass is explored further in Figure 4.3 however the potential confound- ing effect of latitude (the shallowest sites ap- pear to be at lower latitudes) isn’t discussed. The giant kelp’s role in the ecosystem is em- phasised including interesting facts such as its ability to enhance lobster puerulus (larvae) re- tention. Pages 99—104 contain an extensive examination of the role of exposure and water movement on algal species distribution across the region. While interesting, I felt that it probably could have been summarised in a ta- ble and in shorter prose. As in previous parts, there is a synthesis and modelling section at the end, although the very simplistic state- change model shown in Fig 5.16 could probably have been described in a sentence instead. frontiers of biogeography 6.3, 2014 — © 2014 the authors; journal compilation © 2014 The International Biogeography Society

Establishment of Chydorus sphaericus (O.F. Muller, 1785) (Crustacea: Cladocera) in Australia: consequences of mass fish stocking from Northern Europe?

There are 11 species of genus Chydorus Leach, 1816 (Cladocera: Chydoridae) in Australia, including populations of Chydorus sphaericus (O.F. Müller, 1785) morphologically undistinguishable from European ones. Our genetic study of C. sphaericus from two large artificial water bodies in the Adelaide region of South Australia led us to conclude the taxon was introduced to Australia from Europe by human activity, at least in the two studied water bodies. To provide a comprehensive sister-taxa coverage and survey of intraspecific variation, our data were complemented by sequences on Chydorus sphaericus-group from GenBank and Barcode of Life Data Systems website. We speculate that it was related to a mass stocking of introduced species of fishes from Europe. To confirm whether C. sphaericus is an invasive species due to human-mediated introductions, or whether it is a native Australian taxon, further extensive molecular studies (involving nuclear genes) and detailed morphological comparisons are needed. This is a first report on the invasion of a non-daphniid species of Cladocera to Australia. Its significance for Australian ecosystems needs special future studies.

Foundations for the future: A long‐term plan for Australian ecosystem science

AbstractAustralia's ecosystems are the basis of our current and future prosperity, and our national well‐being. A strong and sustainable Australian ecosystem science enterprise is vital for understanding and securing these ecosystems in the face of current and future challenges. This Plan defines the vision and key directions for a national ecosystem science capability that will enable Australia to understand and effectively manage its ecosystems for decades to come. The Plan's underlying theme is that excellent science supports a range of activities, including public engagement, that enable us to understand and maintain healthy ecosystems. Those healthy ecosystems are the cornerstone of our social and economic well‐being. The vision guiding the development of this Plan is that in 20 years' time the status of Australian ecosystems and how they change will be widely reported and understood, and the prosperity and well‐being they provide will be secure. To enable this, Australia's national ecosystem science capability will be coordinated, collaborative and connected. The Plan is based on an extensive set of collaboratively generated proposals from national town hall meetings that also form the basis for its implementation. Some directions within the Plan are for the Australian ecosystem science community itself to implement, others will involve the users of ecosystem science and the groups that fund ecosystem science. We identify six equal priority areas for action to achieve our vision: (i) delivering maximum impact for Australia: enhancing relationships between scientists and end‐users; (ii) supporting long‐term research; (iii) enabling ecosystem surveillance; (iv) making the most of data resources; (v) inspiring a generation: empowering the public with knowledge and opportunities; (vi) facilitating coordination, collaboration and leadership. This shared vision will enable us to consolidate our current successes, overcome remaining barriers and establish the foundations to ensure Australian ecosystem science delivers for the future needs of Australia.

Ecological mechanisms underpinning climate adaptation services.

Ecosystem services are typically valued for their immediate material or cultural benefits to human wellbeing, supported by regulating and supporting services. Under climate change, with more frequent stresses and novel shocks, 'climate adaptation services', are defined as the benefits to people from increased social ability to respond to change, provided by the capability of ecosystems to moderate and adapt to climate change and variability. They broaden the ecosystem services framework to assist decision makers in planning for an uncertain future with new choices and options. We present a generic framework for operationalising the adaptation services concept. Four steps guide the identification of intrinsic ecological mechanisms that facilitate the maintenance and emergence of ecosystem services during periods of change, and so materialise as adaptation services. We applied this framework for four contrasted Australian ecosystems. Comparative analyses enabled by the operational framework suggest that adaptation services that emerge during trajectories of ecological change are supported by common mechanisms: vegetation structural diversity, the role of keystone species or functional groups, response diversity and landscape connectivity, which underpin the persistence of function and the reassembly of ecological communities under severe climate change and variability. Such understanding should guide ecosystem management towards adaptation planning.

The Great Barrier Reef World Heritage Area seagrasses: Managing this iconic Australian ecosystem resource for the future

The Great Barrier Reef World Heritage Area (GBRWHA) includes one of the world's largest areas of seagrass (35,000 km2) encompassing approximately 20% of the world's species. Mapping and monitoring programs sponsored by the Australian and Queensland Governments and Queensland Port Authorities have tracked a worrying decrease in abundance and area since 2007. This decline has almost certainly been the result of a series of severe tropical storms and associated floods exacerbating existing human induced stressors. A complex variety of marine and terrestrial management actions and plans have been implemented to protect seagrass and other habitats in the GBRWHA. For seagrasses, these actions are inadequate. They provide an impression of effective protection of seagrasses; reduce the sense of urgency needed to trigger action; and waste the valuable and limited supply of “conservation capital”. There is a management focus on ports, driven by public concerns about high profile development projects, which exaggerates the importance of these relatively concentrated impacts in comparison to the total range of threats and stressors. For effective management of seagrass at the scale of the GBRWHA, more emphasis needs to be placed on the connectivity between seagrass meadow health, watersheds, and all terrestrial urban and agricultural development associated with human populations. The cumulative impacts to seagrass from coastal and marine processes in the GBRWHA are not evenly distributed, with a mosaic of high and low vulnerability areas. This provides an opportunity to make choices for future coastal development plans that minimise stress on seagrass meadows.

Climate science: A sink down under.

The finding that semi-arid ecosystems in the Southern Hemisphere may be largely responsible for changes in global concentrations of atmospheric carbon dioxide has repercussions for future levels of this greenhouse gas. See Letter p.600 Land and ocean take up around half of the annual anthropogenic carbon emissions, and a thorough understanding of this process is important for predicting future greenhouse gas concentrations and thus climate change. This study investigates the largest uptake of land carbon since atmospheric CO2 measurements began in 1958. Three independent methods of global carbon budget determination point to an exceptionally large land carbon sink in response to extraordinary La Nina rainfall in semi-arid regions in the Southern Hemisphere, with almost 60% of carbon uptake attributed to the Australian ecosystem and an increase in the sensitivity of continental net carbon uptake to precipitation. Tropical rainforests have been thought to dominate the terrestrial processes driving global carbon cycle interannual variability, but this work suggests that semi-arid biomes might become the dominant drivers in future.

Contribution of semi-arid ecosystems to interannual variability of the global carbon cycle.

The land and ocean act as a sink for fossil-fuel emissions, thereby slowing the rise of atmospheric carbon dioxide concentrations. Although the uptake of carbon by oceanic and terrestrial processes has kept pace with accelerating carbon dioxide emissions until now, atmospheric carbon dioxide concentrations exhibit a large variability on interannual timescales, considered to be driven primarily by terrestrial ecosystem processes dominated by tropical rainforests. We use a terrestrial biogeochemical model, atmospheric carbon dioxide inversion and global carbon budget accounting methods to investigate the evolution of the terrestrial carbon sink over the past 30 years, with a focus on the underlying mechanisms responsible for the exceptionally large land carbon sink reported in 2011 (ref. 2). Here we show that our three terrestrial carbon sink estimates are in good agreement and support the finding of a 2011 record land carbon sink. Surprisingly, we find that the global carbon sink anomaly was driven by growth of semi-arid vegetation in the Southern Hemisphere, with almost 60 per cent of carbon uptake attributed to Australian ecosystems, where prevalent La Niña conditions caused up to six consecutive seasons of increased precipitation. In addition, since 1981, a six per cent expansion of vegetation cover over Australia was associated with a fourfold increase in the sensitivity of continental net carbon uptake to precipitation. Our findings suggest that the higher turnover rates of carbon pools in semi-arid biomes are an increasingly important driver of global carbon cycle inter-annual variability and that tropical rainforests may become less relevant drivers in the future. More research is needed to identify to what extent the carbon stocks accumulated during wet years are vulnerable to rapid decomposition or loss through fire in subsequent years.