John C. Z. Woinarski

Ongoing unraveling of a continental fauna: Decline and extinction of Australian mammals since European settlement

Significance The island continent of Australia harbors much of the world’s most distinctive biodiversity, but this review describes an extent of recent and ongoing loss of its mammal fauna that is exceptionally high and appreciably greater than previously recognized. The causes of loss are dissimilar to those responsible for most biodiversity decline elsewhere in the world. The highly distinctive and mostly endemic Australian land mammal fauna has suffered an extraordinary rate of extinction (>10% of the 273 endemic terrestrial species) over the last ∼200 y: in comparison, only one native land mammal from continental North America became extinct since European settlement. A further 21% of Australian endemic land mammal species are now assessed to be threatened, indicating that the rate of loss (of one to two extinctions per decade) is likely to continue. Australia’s marine mammals have fared better overall, but status assessment for them is seriously impeded by lack of information. Much of the loss of Australian land mammal fauna (particularly in the vast deserts and tropical savannas) has been in areas that are remote from human population centers and recognized as relatively unmodified at global scale. In contrast to general patterns of extinction on other continents where the main cause is habitat loss, hunting, and impacts of human development, particularly in areas of high and increasing human population pressures, the loss of Australian land mammals is most likely due primarily to predation by introduced species, particularly the feral cat, Felis catus, and European red fox, Vulpes vulpes, and changed fire regimes.

Monitoring indicates rapid and severe decline of native small mammals in Kakadu National Park, northern Australia

Context. Australia has a lamentable history of mammal extinctions. Until recently, the mammal fauna of northern Australia was presumed to have been spared such loss, and to be relatively intact and stable. However, several recent studies have suggested that this mammal fauna may be undergoing some decline, so a targeted monitoring program was established in northern Australia’s largest and best-resourced conservation reserve. Aims. The present study aims to detect change in the native small-mammal fauna of Kakadu National Park, in the monsoonal tropics of northern Australia, over the period of 1996–2009, through an extensive monitoring program, and to consider factors that may have contributed to any observed change. Methods. The small-mammal fauna was sampled in a consistent manner across a set of plots established to represent the environmental variation and fire regimes of Kakadu. Fifteen plots were sampled three times, 121 plots sampled twice and39plotsonce.Resamplingwastypicallyat5-yearlyintervals.Analysisusedregression(ofabundanceagainstdate),and Wilcoxon matched-pairs tests to assess change. For resampled plots, change in abundance of mammals was related to fire frequency in the between-sampling period. Key results. A total of 25 small mammal species was recorded. Plot-level species richness and total abundance decreased significantly, by 54% and 71%, respectively, over the course of the study. The abundance of 10 species declined significantly, whereas no species increased in abundance significantly. The number of ‘empty’ plots increased from 13% in 1996 to 55% in 2009. For 136 plots sampled in 2001–04 and again in 2007–09, species richness declined by 65% and the total number of individuals declined by 75%. Across plots, the extent of decline increased with increasing frequency of fire. The most marked declines were for northern quoll, Dasyurus hallucatus, fawn antechinus, Antechinus bellus, northern brown bandicoot, Isoodon macrourus, common brushtail possum, Trichosurus vulpecula, and pale fieldrat, Rattus tunneyi. Conclusions. The native mammal fauna of Kakadu National Park is in rapid and severe decline. The cause(s) of this declinearenotentirelyclear,andmayvaryamongspecies.Themostplausiblecausesaretoofrequent fire,predationbyferal cats and invasion by cane toads (affecting particularly one native mammal species). Implications. The present study has demonstrated a major decline in a key conservation reserve, suggesting that the mammal fauna of northern Australia may now be undergoing a decline comparable to the losses previously occurring elsewhere in Australia. These results suggest that there is a major and urgent conservation imperative to more precisely identify, and more effectively manage, the threats to this mammal fauna.

The Nature of Northern Australia: Natural Values, Ecological Processes and Future Prospects

The book offers a synthesis of the natural values and ecology of north Australia together with recommendations for actions needed to maintain these values. The book’s authors, John Woinarski (NRETA), Brendan Mackey (ANU), Henry Nix (ANU) and Barry Traill (Pugh Foundation, formerly The Wilderness Society) have brought together a great deal of recent research in these areas, much of it enabled by the TS–CRC partners, particularly through John Woinarski and NRETA.

The role of connectivity in Australian conservation

The existing system of nature reserves in Australia is inadequate for the long-term conservation and restoration of native biological diversity because it fails to accommodate, among other elements, large scale and long-term ecological processes and change, including physical and biotic transport in the landscape. This paper is an overview of the connectivity elements that inform a scientific framework for significantly improving the prospects for the long-term conservation of Australias biodiversity. The framework forms the basis for the WildCountry programme. This programme has identified connectivity at landscape, regional and continental scales as a critical component of an effective conservation system. Seven categories of ecological phenomena are reviewed that require landscape permeability and that must be considered when planning for the maintenance of biological diversity and ecological resilience in Australia: (1) trophic relations at regional scales; (2) animal migration, dispersal, and other large scale movements of individuals and propagules; (3) fire and other forms of disturbance at regional scales; (4) climate variability in space and time and human forced rapid climate change; (5) hydroecological relations and flows at all scales; (6) coastal zone fluxes of organisms, matter, and energy; and, (7) spatially-dependent evolutionary processes at all scales. Finally, we mention eight cross-cutting themes that further illuminate the interactions and implications of the seven connectivity-related phenomena for conservation assessment, planning, research, and management, and we suggest how the results might be applied by analysts, planners, scientists, and community conservationists.

The effects of grazing and fire on vegetation and the vertebrate assemblage in a tropical savanna woodland in north-eastern Australia

We studied the response of vegetation and vertebrate assemblages to fire and grazing, and their interacting effects, in Eucalyptus woodland in north-eastern Australia. In this vegetation type, many pastures remain free of cattle grazing due to the occurrence of a native shrub poisonous to livestock. Vegetation (floristic data and 22 habitat variables) and vertebrate fauna (birds, mammals, reptiles) were sampled in 29 standardized 50 × 50-m quadrats in the 2001 wet season, representing four treatments: sites burnt recently (within 2 y) and grazed by cattle (4–8 ha per livestock unit); sites unburnt (last burnt >2 y ago) and grazed; sites burnt recently and ungrazed; and unburnt and ungrazed sites. Fire and grazing had a significant influence on vegetation: both grazing and fire reduced ground cover (fire in grazed sites 51–23%, fire in ungrazed sites 68–39%) and increased the cover of forbs (8% in burnt and grazed sites, 3% if ungrazed) and tussock grasses (20% in grazed and unburnt sites and 5% when ungrazed). Grazing caused a shift in floristic composition from the perennial hummock grass Trioda pungens to tussock grasses (e.g. Aristida spp., Enneapogon spp.), forbs (e.g. Phyllanthus spp.) and shrubs (e.g. Acacia spp.). Of the vertebrate groups, birds responded more to fire effects (9 species), reptiles to grazing effects (6 species) and mammals to the interaction (2 species). Species reacted to increases in bare ground (e.g. crested pigeon Ocyphaps lophotes , hooded robin Melanodryas cucullatus , Ctenophorus nuchalis ) and to the dominant ground cover (e.g. Ctenotus pantherinus ) or change in vegetation architecture (e.g. singing honeyeater Lichenostomus virescens , variegated fairy-wren Malurus lamberti ). The clearest example of an interacting effect was the cycle of complementary dominance between the rodents Pseudomys delicatulus and P. desertor , the latters post-fire recovery becoming more muted in sites where cattle grazed (modelled time for population recovery twice as long as in ungrazed sites).

Landscapes without boundaries: wildlife and their environments in northern Australia

This paper provides an introduction to the ecological fabric of northern Australia, described here as being a land characterised by extreme climatic seasonality and largely devoid of marked topographic features. Largely as a result of the latter trait, many species have extensive geographic ranges, and the spatial turnover in species composition is extremely limited. Somewhat counter-intuitively, these two traits can be accommodated by organisms only through reliance on critical, but often subtle, landscape variation. We present some preliminary models for Gouldian finch (Erythrura gouldiae) and black-footed tree-rat (Mesembriomys gouldii) to illustrate patterns of variation in their resource availability, and the consequences of such variation. We discuss briefly some studies that have attempted to integrate, or at least consider, these elements.

Conservation of mobile species in a variable environment: The problem of reserve design in the Northern Territory, Australia

Mobility and massive population fluctuations in response mainly to a highly variable climate are pervasive features of the wildlife of both the monsoonal and the arid halves of the Northern Territory, Australia. These characteristics defy the adequate conservation of these species in a conventional system of formal reserves, and pose substantial problems for reserve design. We argue that protection of the still extensive natural vegetation outside the reserve system will be vital for the persistence of mobile species in this landscape.

Distribution patterns of vertebrates in relation to an extensive rainfall gradient and variation in soil texture in the tropical savannas of the Northern Territory, Australia

The abundance, richness and species composition of frog, reptile, bird and mammal faunas varied along an extensive gradient from 470 to 1406 mm annual rainfall, and between three contrasting soil types (clay, loam and sand) in northern Australia. Patterns varied between and within vertebrate classes. In general, the most fertile soils in the highest rainfall sites supported the greatest species richness and abundance, but this association with fertility broke down at lower rainfall sites. Frogs were richest and most abundant at high rainfall sites, especially on clay soils, presumably because these had greatest water availability. Clay soils supported few reptile species, but these were often at relatively high abundance. High rainfall sites supported the richest reptile faunas. On sand and loam soils, bird species richness varied little along the rainfall gradient, but richness declined very substantially on clay soils. This was probably largely due to the far more marked vegetation structural change on clay soils than on other substrates. Few mammals were reported, and no clear trends were associated with either rainfall gradient or soil texture. Turnover in species composition along the rainfall gradient was gradual and limited on sand and loam soils, but far more marked on clay soils. There were few cases of replacements of ecologically comparable species along the gradient. These patterns reflect the disparate history, fragmentation and landscape positioning of clay soil environments, relative to the far more homogeneous eucalypt-dominated vegetation on sand and loam soils. Although comparable studies are lacking on other continents, patterns revealed here may be idiosyncratic due to the virtual monopolisation by eucalypts of the environment across the very extensive rainfall gradient.

Distributional pattern of plant species endemic to the Northern Territory, Australia

The distributions of the 567 plant species considered to be endemic to the Northern Territory, Australia, were collated from a distributional database comprising about 600 000 records. Endemic species comprise a non-random taxonomic subset of all plants known from the Northern Territory. Because of substantial geographic disparity in collecting effort, we analysed geographic patterning of these endemic species by using both (1) actual records only and (2) interpolated ranges (minimum convex polygons). The geographic distribution of the number of Northern Territory endemic plant species was well predicted by a measure of topographic complexity and climate (particularly rainfall). The observed distributional patterning of endemic species was also influenced by survey effort, but this latter influence was substantially reduced by the use of minimum convex polygons. Both analyses revealed that there was a clear aggregation of endemic species in the 32 000 km2 of the sandstone plateau of western Arnhem Land. This ‘hotspot’ has been previously recognised in coarser-scale assessments of national and international centres of plant biodiversity. Our analysis concluded that 172 species are restricted to this plateau, and that the plateau comprised at least 90% of the distribution of a further 25 species. More broadly, 438 plant species are endemic to the northern part of the Northern Territory (the 316 000 km2 north of 16°S), a level of endemism that may match that of Cape York Peninsula and surpasses that of the Kimberley. The core area for Northern Territory endemic plants, the plateau of western Arnhem Land, is currently threatened, particularly by unfavourable fire regimes.

Conservation and the maintenance of biodiversity in the rangelands

There has been substantial loss of biodiversity in the Australian rangelands, and evidence suggests that the attrition is continuing. We argue that rangeland users should be more aware of, and concerned about, this problem: that we are sullying an international asset; that we are undermining the basis of a major rangeland industry, tourism; that we are sabotaging the potential for the development of alternative rangeland uses (most notably sustainable use of native wildlife); that such losses provide evidence that we are poor managers; that such losses diminish our lives; that such losses indicate that at least some of our environments are operating at reduced functionality; and that such losses take away or reduce important and wide-ranging environmental services. This loss is due to a complex array of factors, each affecting different components of biodiversity in different ways. Our responses are generally poorly coordinated across rangeland jurisdictions, and there is uncertainty about responsibilities across different land tenures. Given the diffuse but pervasive nature of the problem and the generally poorly coordinated and non-strategic current response, we suggest that biodiversity conservation needs to be far more clearly and systematically operationalised, that a clear goal for biodiversity conservation in the rangelands (maintenance of viable populations of all native species of plants and animals at appropriate spatial and temporal scales) needs to be developed, and that, from this, the community needs to set explicit targets relating to this goal, at continental, jurisdiction, regional and property scales. While we recognise that our existing knowledge base is imperfect, such limitation should not delay the implementation of these steps. We consider that there is sufficient management expertise to realise a rangeland biodiversity goal. However, there are two more serious impediments in achieving the goal: current lack of resources and of societal agreement.