Jennifer Silcock

Managed livestock grazing is compatible with the maintenance of plant diversity in semidesert grasslands.

Even when no baseline data are available, the impacts of 150 years of livestock grazing on natural grasslands can be assessed using a combined approach of grazing manipulation and regional-scale assessment of the flora. Here, we demonstrate the efficacy of this method across 18 sites in the semidesert Mitchell grasslands of northeastern Australia. Fifteen-year-old exclosures (ungrazed and macropod grazed) revealed that the dominant perennial grasses in the genus Astrebla do not respond negatively to grazing disturbance typical of commercial pastoralism. Neutral, positive, intermediate, and negative responses to grazing disturbance were recorded amongst plant species with no single life-form group associated with any response type. Only one exotic species, Cenchrus ciliaris, was recorded at low frequency. The strongest negative response was from a native annual grass, Chionachne hubbardiana, an example of a species that is highly sensitive to grazing disturbance. Herbarium records revealed only scant evidence that species with a negative response to grazing have declined through the period of commercial pastoralism. A regional analysis identified 14 from a total of 433 plant species in the regional flora that may be rare and potentially threatened by grazing disturbance. However, a targeted survey precluded grazing as a cause of decline for seven of these based on low palatability and positive responses to grazing and other disturbance. Our findings suggest that livestock grazing of semidesert grasslands with a short evolutionary history of ungulate grazing has altered plant composition, but has not caused declines in the dominant perennial grasses or in species richness as predicted by the preceding literature. The biggest impact of commercial pastoralism is the spread of woody leguminous trees that can transform grassland to thorny shrubland. The conservation of plant biodiversity is largely compatible with commercial pastoralism provided these woody weeds are controlled, but reserves strategically positioned within water remote areas are necessary to protect grazing-sensitive species. This study demonstrates that a combination of experimental studies and regional surveys can be used to understand anthropogenic impacts on natural ecosystems where reference habitat is not available.

Oases to Oblivion: The Rapid Demise of Springs in the South‐Eastern Great Artesian Basin, Australia

Introduction Since the advent of powerful rock boring equipment in the late nineteenth century, ground water extraction for towns, mining, and agriculture has had significant impacts on aquifers across the globe. In areas where surface water is scarce, human demands on artesian supplies have been particularly acute, demonstrated by declines in the pressure surface of aquifers and subsequent loss of artesian springs. The springs and the wetlands they support have important natural values, providing habitat for specialized plants and animals, many of which are endemic to their idiosyncratic habitat (Ponder 1986; Patten et al. 2008). Springs are also significant cultural places, embodying traditional folk-lore, and mythology (Idris 1996; Park and Ha 2012) and supporting settlements along ancient trade routes (Aldumairy 2005). While the exploitation of groundwater and loss of springs, together with their natural resource and cultural values, has been repeated across the continents from Australia (Fairfax and Fensham 2002), the United States (Keleher and Rader 2008; Brune 1981), China (Jiao 2010) and North Africa (Roberts and Mitchell 1987; Idris 1996) there have been few comprehensive historical studies which piece together the details of their decline. In recent decades there have been attempts to resurrect the forgotten cultural history of the Australian Great Artesian Basin (GAB) springs. There are broad cultural and historical examinations of the GAB, its folklore and its significance to the historical geography of central Australia (Powell 2012; Powell 1991; Blake and

Ecological consequences of land clearing and policy reform in Queensland

Land clearing threatens biodiversity, impairs the functioning of terrestrial, freshwater, and marine ecosystems, and is a key contributor to human-induced climate change. The rates of land clearing in the State of Queensland, Australia, are at globally significant levels, and have been the subject of intense and polarised political debate. In 2016, a legislative bill that aimed to restore stronger controls over land clearing failed to pass in the Queensland Parliament, despite the clear scientific basis for policy reform. Here, we provide a short history of the recent policy debate over land clearing in Queensland, in the context of its global and national ecological significance. Land clearing affects regional climates, leading to hotter, drier climates that will impact on the Queensland economy and local communities. Loss of habitat from land clearing is a key threatening process for many endangered animals and plants. Runoff from land clearing results in sediment and nutrient enrichment, which threatens the health of the Great Barrier Reef. Australia has made national and international commitments to conserve biodiversity and reduce our greenhouse gas emissions, but current land clearing policies are not consistent with these commitments. Stronger regulation is needed to reduce vegetation loss, such as target-based regulation, which sets a cap on land clearing and could effectively halt vegetation loss over the long term. Lasting policy reform is required, and we recommend an effective policy mix that restricts clearing, provides economic opportunities for vegetation retention, and informs the Australian community about the value of native vegetation.

Lost in time and space: re-assessment of conservation status in an arid-zone flora through targeted field survey

Lack of basic data to assess plant species against IUCN Red List criteria is a major impediment to assigning accurate conservation status throughout large areas of the world. Erroneous assessments will be most prevalent in vast poorly surveyed areas where herbarium collections are sparse. In arid environments, assessments are further confounded by extreme temporal variability and poor understanding of the nature and magnitude of threats. We systematically re-assess the conservation status of an arid-zone flora. The status of all 1781 vascular plant species occurring across 635 300 km2 of inland eastern Australia was initially assessed through herbarium records and expert interviews. This process generated a list of apparently rare and potentially threatened species, which guided a targeted survey program over 4 years. Search effort and key data on populations of candidate species found were recorded and used to assess 91 species against IUCN criteria. One-third of species were widespread and abundant at least in certain seasons, but had been deemed rare due to sparse collections. The conservation status of 20, mostly newly recognised species from restricted habitats, was upgraded and 14 remained listed because of having restricted areas of occupancy. With the exception of 12 artesian spring species, continuing declines were documented for just six species. The criterion that allows for listing of species because of extreme fluctuations (in combination with restricted and fragmented populations) needs to be carefully interpreted in arid zones, where these fluctuations may be apparent rather than real, and may actually confer resilience to grazing for some species. Our approach facilitates robust conservation assessments across vast and poorly known arid regions, distinguishing species that have merely been lost in space and time from those that are at risk of extinction.

Assessing rarity and threat in an arid-zone flora

An understanding of rarity and how it relates to extinction risk is a central concern of conservation biology. Classic conceptions of rarity revolve around spatial rarity, based on distribution and abundance, rather than temporal rarity, where species may be common following certain conditions but rare for most of the time. This form of rarity is likely to be especially prevalent in highly variable arid systems. Rarity in the arid zone is also characterised by poorly understood threats, such as grazing, and may also reflect low collection effort given the vast and inaccessible areas involved. This study explores rarity and threat in the arid zone, based on the flora of a large region of western Queensland. The status of all species known to occur in the study area was systematically assessed, and the current list of threatened species was examined for bias in forms of rarity, life forms and habitats. Five threat syndromes were identified, arising from the interaction of plant biology and threatening processes. Over 60 potentially threatened species have been overlooked in the listing process. The list is dominated by narrow endemics from residual and spring habitats and the species from springs at least are genuinely threatened. Widespread but sparsely occurring species are under-represented in the current list, as are grasses. With the exception of spring-dependent species, plant conservation in western Queensland is currently constrained by lack of basic data on distribution, abundance, population dynamics and realistic threat syndromes for nearly all species. Separating the influence of genuine rarity, temporal rarity and low collection effort, as well as a more detailed understanding of threatening processes are needed to address plant conservation in the arid zone.

In Search of Lost Springs: A Protocol for Locating Active and Inactive Springs

Groundwater springs are significant landscape features for humans and the biota that occupies their habitat. Many springs become inactive where groundwater exploitation by humans has lowered the water table or artesian pressure. In order to assess this impact, it is important to identify and locate active, and with more difficulty, inactive springs. Using a variety of archival, environmental and field-based data, this study presents a protocol for the determination of the location and status of springs across the Great Artesian Basin of Australia. This protocol underpins a database of springs, which is not only important for the assessment of spring ecosystems, but also contributes to understand groundwater extraction impacts and hydrogeological processes. The database indicates that 30.0% of discharge (artesian) springs in the Great Artesian Basin are entirely inactive and another 11.8% are partially inactive. For the outcrop (gravity) springs of the Basin, only 1.9% are entirely inactive and 7.4% partially inactive, and for the outcrop springs in the Tertiary sandstone overlying the Basin 30.9% are inactive and 18.2% are partially inactive.

Understanding and managing the threats to Night Parrots in south-western Queensland

ABSTRACT South-western Queensland supports a suite of threatened native species, including Night Parrots. We investigated why this species has persisted in the region and discovered low prevalence of the typical factors that are thought to explain fauna attrition elsewhere in central Australia. Foxes appear to be completely absent. Feral cats were recorded relatively infrequently and showed a significant preference for habitats less commonly used by Night Parrots, a partition that may be driven by the presence of dogs that were detected twice as frequently as cats. Our study area has had a long history of moderate grazing pressure, which is concentrated mostly in productive alluvial habitats. We detected very few herbivores, and dog scat analyses suggest that macropod populations are regulated by predation. Archival imagery shows that large fires are not a feature of this landscape, resulting in the long-term, stable availability of patchy Triodia habitats separated by natural no-fuel areas. Based on these empirical data, we postulate that low non-native predator pressure, long-term stable availability of Triodia cover and a productive landscape that has had only moderate grazing pressure are the interacting factors that may explain why Night Parrots have persisted in south-western Queensland. We present practical management actions that could enhance the suitability of this landscape for Night Parrots.

Observations on breeding Night Parrots (Pezoporus occidentalis) in western Queensland

ABSTRACT A population of Night Parrots (Pezoporus occidentalis) was discovered in 2013 in western Queensland and has become the primary focus of efforts aimed at conserving habitat and protecting the species from extinction. Critical information on nesting habitat and location, breeding season and behaviour, clutch size and breeding success is currently limited to anecdotal 19th-century observations and accounts by early natural historians. Here we describe several breeding attempts at Pullen Pullen Reserve. Our observations include nest and fledgling descriptions, habitat and clutch characteristics, breeding seasonality, adult breeding behaviour and vocalisations. We also identify a King Brown Snake (Pseudechis australis) as the predator responsible for one nesting failure. Our observations confirm historical reports of nesting habitat, egg and clutch size and breeding seasonality and provide important new information on vocalisations and adult behaviour around an active nest. These new data provide a basis for future studies and conservation management of this enigmatic threatened species.

A 150-year fire history of mulga (Acacia aneura F. Muell. ex Benth.)dominated vegetation in semiarid Queensland, Australia

Changes to fire regimes associated with European colonisation are implicated in declines in biodiversity and productivity in rangelands globally. However, for many areas there is incomplete knowledge of historical fire regimes and purported changes can become accepted wisdom with little empirical evidence. In the Mulga Lands of south-western Queensland, the dominant narrative implicates reduced fire frequency as a cause of woody vegetation thickening. We present a fire history of the Mulga Lands since pastoral exploration in the 1840s based on a review of explorer and early pastoralist journals, newspaper articles, interviews with long-term landholders and collation of satellite imagery. Fires in mulga communities are infrequent and only occur after at least two years of above-average summer rainfall. The assumption of regular pre-pastoral fires is not supported by available evidence. Since pastoral settlement in the 1860s, fire events affecting >1000 km2 have occurred seven times (1891–1892, 1904, 1918, 1950–1951, 1956–1957, 1976–1979 and 2011–2013), with only the 1950s fires affecting a >10% of the total area of mulga-dominated vegetation. We argue that fire is limited by fuel loads, which are in turn limited by rainfall events occurring only a few times a century. Even in the absence of grazing and active fire suppression fire intervals would be extremely long, perhaps 30–50 years in relatively fire-prone communities and much longer throughout most of the region. Combined with quantitative studies of fire and tree and shrub population dynamics, detailed fire histories will allow for more informed and nuanced debates about the role of fire in rangelands subject to abrupt management upheavals.

Subtropical native grasslands may not require fire, mowing or grazing to maintain native-plant diversity

The rarity of native grasslands in agricultural districts heightens the requirement for optimal management to maintain diversity. Previous studies have suggested that disturbance is required to maintain species diversity in temperate Australian grasslands, but grasslands in semiarid environments do not have the same disturbance requirement. The current study examines the short-term responses to disturbance of subtropical grassland of the Darling Downs, south-eastern Queensland. We also compare temperate and subtropical grasslands in terms of biomass and rainfall. A field experiment was established with treatments, including burning in 2013, burning in 2014, burning in both years, mowing in both years, mowing and raking in both years, and an undisturbed control. Treatments were replicated at each of seven sampling stations in similar environments. The initial sampling after 2013 followed a wet summer and the final sampling was in 2015 after a dry summer. Non-metric multi-dimensional scaling showed that environmental differences, including silt content, soil pH, waterlogging and rainfall history, had more effect on the variation in species composition than did the treatments. The treatments engendered no significant response in species diversity. Of 51 widespread species, only four had a significant change in abundance in response to treatment. Herbaceous biomass was higher in temperate than subtropical grassland after a dry period. The grassland sward may be more open in the subtropics than in temperate grassland because of higher decomposition rates. A comparison of rainfall distribution between subtropical grassland and temperate grassland indicated that droughts are much more frequent in the former environments. These occasional droughts may provide a stress that reduces perennial grass cover, supplanting the requirement for grazing or fire to maintain plant diversity in grasslands. The management of grassland remnants in the subtropics, therefore, seems straightforward because there is little response in species richness or composition to disturbance. However, soil disturbance should be avoided to ensure that exotic species do not proliferate.