Linking life history to landscape for threatened species conservation in a multiuse region

Landscape-scale conservation that considers metapopulation dynamics will be essential for preventing declines of species facing multiple threats to their survival. Toward this end, we developed a novel approach that combines occurrence records, spatial-environmental data, and genetic information to model habitat, connectivity, and patterns of genetic structure and link spatial attributes to underlying ecological mechanisms. Using the threatened northern quoll (Dasyurus hallucatus) as a case study, we applied this approach to address the need for conservation decision-making tools that promote resilient metapopulations of this threatened species in the Pilbara, Western Australia, a multiuse landscape that is a hotspot for biodiversity and mining. Habitat and connectivity were predicted by different landscape characteristics. Whereas habitat suitability was overwhelmingly driven by terrain ruggedness, dispersal was facilitated by proximity to watercourses. Although there is limited evidence for major physical barriers in the Pilbara, areas with high silt and clay content (i.e., alluvial and hardpan plains) showed high resistance to dispersal. Climate subtlety shaped distributions and patterns of genetic turnover, suggesting the potential for local adaptation. By understanding these spatial-environmental associations and linking them to life-history and metapopulation dynamics, we highlight opportunities to provide targeted species management. To support this, we have created habitat, connectivity, and genetic uniqueness maps for conservation decision-making in the region. These tools have the potential to provide a more holistic approach to conservation in multiuse landscapes globally.

The Potential of Some Mechanical Treatments for Rehabilitating Arid Rangelands I. Within-Site Effects and Economic Returns

Attempts to rehabilitate degraded arid rangelands do not always succeed, and we perceived a need for some simple ecological indicators which would help determine whether mechanical intervention was likely to be useful. In this first of two papers, we largely focus on the effect of pitting and opposed discing, although we consider ripping and exclosure briefly, at 26 locations in central Australia. Pits and furrows successfully trapped erosion products and supported more basal cover and a greater number of plants than inter-furrow mounds or untreated areas. In addition, a number of soil variables were altered by the treatments. However, economic returns were unlikely to exceed outlays in most of the cases we considered. The best returns are predicted where degradation is minor, where livestock are of high quality and where landholders collect their own seed. Exclusion of grazing in the initial stages will enhance the amount of plant cover.

The Potential of Some Mechanical Treatments for Rehabilitating Arid Rangelands Ii. Identifying Indicators From Between-Site Comparisons

In a companion paper we showed that degraded rangelands in central Australia could rarely be rehabilitated economically with mechanical treatments like pitting and opposed discing. In this paper we devise a set of environmental indicators to guide the selection of areas which might respond to treatment, by exploring the relationships between a wide variety of environmental attributes, the types of treatment and the responses of different groups of plants. The best response of palatable perennials to these mechanical treatments was likely on soils with no more clay than a sandy clay loam, and where average annual rainfall was at least 280 mm. Well developed micro-relief in the soil surface and a crust that was reasonably penetrable when dry and stable when wet were also useful though less important as indicators of likely plant response. Generally, land with these attributes in central Australia is unlikely to be severely degraded. Treatment structures do not persist in soils of high clay content. Buffel grass (Cenchrus ciliaris L.), an exotic species commonly introduced with treatment, does not thrive in clayey soils, and can invade untreated, better potential areas. The alternatives of larger-scale water ponding or harvesting, and the use of native species, should be considered for degraded soils. Rapid comparative assessments of the response of plants to treatment can be made by counting all perennials with a basal diameter of 25 cm within a standard area.