Assemblage Patterns and Environmental Gradients in The

Chapter 1. Introduction. Introduction Approximately 20% of continental Australia consists of tropical savanna rangelands. These are defined as landscapes of dense native grasses and scattered trees, grazed by cattle, but where rainfall is too low to permit intensive agriculture (Harrington et al. 1984). Despite this geographical extent, there is perhaps some bias of ecological research to coastal and temperate environments due to the proximity to population centres and the presence of charismatic and species-rich ecological communities (compare papers in Ash 1996 with Hobbs and Yates 2000). Biophysical conceptual frameworks for rangeland management have been proposed (Morton 1990; Pickup and Stafford-Smith 1993; James et al. 1995), but with little subsequent specific bioregional research (Landsberg et al. 1997; Fisher 2001a). While some rangeland biota and assemblages are species rich and well studied (Dickman et al. 1999; Morton 1993; Fisher 2001a), on the whole data are deficient (Woinarski et al. 2001a). In Australia there is explicit government policy that recognises the need for Ecologically Sustainable Development (Commonwealth Government 1996b) and specifically in rangelands (ANZECC and ARMCANZ 1999). Coupled with this is the goal of developing reserve systems that are comprehensive, representative and adequate for the protection of biodiversity (JANIS 1997). There is clear evidence that government targets proposed for remnant vegetation protection (10-30%) are too low and will lead to dramatic species loss (Barrett 2000; James and Saunders 2001). Therefore, off-reserve conservation is a vitally important adjunct to formal reserve systems (Hale and Lamb 1997; Queensland Government 2001). This requires practical guidelines, management techniques and policy conducive for pastoral land managers to improve the conservation gains in production environments (Lambeck 1999; BIOGRAZE 2000). Conservation management in Australia is currently undertaken within a bioregion- planning framework (Thackway and Creswell 1995). Land classifications are Chapter 1. Introduction commonly used as the foundation for selection of areas to reserve (Pressey 1994), and a system of land classification fundamentally underpins much conservation planning in Queensland (Sattler and Williams 1999). The objective of such planning is often to efficiently select areas for reserves in order to maximise representativeness of biota and landscapes (Vane-Wright 1991; Pressey et al. 1993). This process is heavily reliant on data on the biodiversity values of particular sites or regions (Prendergast et al. 1998), or where data are not available, the use of surrogates that represent spatial patterns of biodiversity (Flather et al. 1997). However the value of many surrogates for other aspects of biodiversity is uncertain. Few studies have examined the direct relationship of fauna distribution to a priori classifications (Pressey 1994). A characteristic of the tropical savannas of northern Australian is the combination of climatic seasonality and gradual environmental variation over large geographic areas (Williams et al. 1996b; Ludwig et al. 1999b; Woinarski 1999b; Cook and Heerdegen 2001). Resources pulse in short intense wet seasons, then decline to an extended nadir through the dry season. In response, biotas are mobile and flexible, or contract to refugia or local extinction (Woinarski 1999a, b; Woinarski et al. 1992c; Franklin 1999). Savanna flora and fauna could be considered mutable, resource and climate-driven entities. Objectives of Study A problem that becomes apparent in any review of ecological patterns and processes in Australian tropical savanna rangelands is the lack of adequate biological data on patterns of biodiversity. This is especially true in northern Queensland. Regional fauna surveys for conservation planning have been sporadically conducted (see review in chapter 3; Kirkpatrick and Lavery 1979), but a large degree of this work has been opportunistic and descriptive in nature. Therefore much of the information is of little value in conservation planning, a process which requires accurate species localities and quantification of abundance and environmental pattern. In Queensland there is also a stark disparity between vertebrate fauna studies concentrating on the extensive savanna rangelands (see reviews in Sattler and Williams 1999; Woinarski et al. 2001a), and 19 Chapter 1. Introduction coastal and species-rich bioregions such as the Wet Topics that are very well studied (see review in Abrahams et al. 1995; Williams et al. 1996c). James et al. (1995) recommended a framework for undertaking research and conservation planning in Australia’s rangelands, with these four themes: 1. identifying spatial and temporal patterns of distribution of native biota; 2. quantifying the impact of pastoralism on native fauna; 3. identifying and controlling feral pest species; and 4. developing concepts and tools for regional conservation planning. Fisher (2001a) suggests that in tropical savanna rangelands, a further theme should be added: identifying the effects of fire, and developing tools for its management. The primary overarching objective of this study was to examine the patterns within, and environmental controls on, the vertebrate fauna assemblage in one of Queensland’s tropical savanna bioregions: the Desert Uplands. This region embodies one of the classic dilemmas for rangeland managers in Queensland: the pace of development is outstripping the available knowledge of the ecology of the natural systems. Information for adequate and sustainable industry and conservation planning is lacking. In undertaking this study I examine three of the themes proposed above (excluding the question of feral pest species), but incorporating consideration of fire to the assessment of impacts of pastoralism. Though these are explicitly focussed on management, they also correspond to a hierarchy of processes considered to contribute to patterns of species-richness and diversity, namely: local ecological interactions and process, regional spatial and temporal variation in assemblage and environmental patterns, and broader biogeographic influences (Schluter and Ricklefs 1993). The impact of feral cats on native fauna was also examined as part of the study, and a total of 194 catguts were collected over a 2-year period, consisting of 1300 prey items. However, due to constraints of time and thesis length, analysis and discussion of this data were excluded from the final dissertation and will be published separately at a later date. 20 Chapter 1. Introduction Conservation planning in Queensland is currently focussed on regional ecosystems, a unit assumed to be a surrogate for fauna patterns (see chapter 4). The emphasis in the regional ecosystem approach on mapping vegetation (by dominant plant species) and geological and soil parameters is possibly due to widespread existing data primarily generated for agricultural needs (e.g. Turner et al. 1993), and high availability of aerial- photo and satellite imagery for remote interpretation of vegetation, geology and soil (Burrough and McDonnell 1998). The paucity of previous bioregional fauna surveys in northern Queensland suggests that these have been considered too expensive and time consuming. This is the challenge facing government agencies with inadequate resources and a business culture shift from long-term strategic biodiversity conservation to one of managerialism and the balance of political risk (Beckwith and Moore 2001). However, strategic protection of fauna species under high pressure of rapid landscape change still requires some primary data regarding habitat relationships and distribution, beyond simple retention rules or mapping of surrogates. Furthermore the choice of the Desert Uplands was not random. The bioregion was selected as a national priority for examination due to the rapid rate of tree clearing currently affecting the area, and the low level of reservation and (typically) meagre information regarding its native biota. In conclusion there are four specific objectives of this study: • What is the zoogeographic context of the Desert Uplands bioregion, in particular, is the fauna assemblage distinctive or comparable to other northern Australian bioregions, and has its geographic location (on a significant topographic discontinuity, the Great Dividing Range) influenced composition and pattern of vertebrate fauna? • What are the regional patterns of spatial distribution of the fauna composition and assemblage, and what are the environmental determinants of these? • How might the patterns of fauna and flora assemblage within regional ecosystems influence conservation planning in the bioregion, and are the patterns of biota complementary with existing land classifications? • What is the influence of local scale interactions on the patterns of flora and fauna assemblage, in particular cattle grazing and fire, and how does this influence within- habitat variation? 21 Chapter 1. Introduction Structure of Thesis In the remainder of chapter 1, I provide an overview of the environment and landscapes of the Desert Uplands bioregion. I go on to describe the framework of conservation planning in Queensland - that is the system of bioregions, subregions, landzones and regional ecosystems. I also review the current state of regional ecosystem information available for the Desert Uplands, and existing information regarding flora and fauna, and biota of conservation significance. I briefly describe the nature of

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