Ongoing destruction of critical rock habitat threatens biodiversity

Author: Damian Michael (Charles Sturt University), dmichael@csu.edu.au

With over 220 vertebrate species, Australia has a rich diversity of wildlife associated with, and in many cases, dependent on rocky environments and component microhabitat features such as surface rock. In all their complexity and form, rocky outcrops support a rich diversity of endemic species, are collectively referred to as biological hotspots, and represent refugia for specialised plants and animals, including more than 55 species listed as nationally threatened.

Despite their well-recognised ecological, cultural and economic values, rock formations are fragile ecosystems, easily degraded by human activities and lack adequate levels of protection on private land. The impacts of rock removal on the population viability of the threatened rock-dwelling broad-headed snake (Hoplocephalus bungaroides) is well-established. However, limited assessment of rock-dwelling vertebrate communities, especially in agricultural landscapes, makes it difficult to determine the spatial extent of threatened faunal groups and the impacts associated with landscape transformation and farmland intensification.

Recent developments in broad-acre cropping technology has triggered a rapid increase in the removal of surface rock habitat from across Australia’s prime agricultural landscapes. Whilst not illegal, the removal of bush rock is listed as a key threatening process under the Threatened Species Conservation Act 1995 (TSC Act). The new wave of habitat loss associated with rock-crushing machinery has massive implications for nationally threatened reptile species such as the pink-tailed worm-lizard, striped legless lizard and grassland earless dragon species, which are on the brink of extinction. This practice is at odds with the current philosophy of sustainable farming, whereby agricultural activities and wildlife conservation can co-occur on the same land with mutual conservation and economic benefits. Pressure to maximise productivity by increasing crop yields and intensifying land use could spell disaster for threatened species that primarily occur on farmland.

There is urgent need to develop high resolution maps of critical rock refugia, spatially explicit species distribution models, and improve our understanding of the attributes of rock microhabitat that are important for threatened species, to reduce ongoing biodiversity declines in commodity production landscapes.

A downloadable pdf on this Hot Topic can be found here.

Research Entries

Title

Aims

Results

Couper, P., & Hoskin, C. (2008) Litho-refugia: the importance of rock landscapes for the long-term persistence of Australian rainforest fauna. Australian Zoologist, 34(4), 554-560.

To outline examples of rainforest fauna that exemplify the importance of rock landscapes in the persistence of rainforest lineages.

The stability of rock habitats means that they have acted as refugia for the persistence of rainforest lineages that may otherwise have disappeared from regions due to rainforest contraction resulting from climatic change. Rock habitats have therefore played an important role in maintaining the diversity of Australia’s rainforest fauna.

Fitzsimons, J. A., & Michael, D. R. (2017) Rocky outcrops: a hard road in the conservation of critical habitats. Biological conservation, 211, 36-44.

A review of the literature on the ecological, cultural and economic values of rocky outcrops, threatening processes and conservation solutions.

Rocky outcrops are examples of small natural features with an ecological role extending beyond their area. They provide long-lasting landscape features with stable micro-climates and ecological refuges. Rocky outcrops provide habitat for a range of endemic, range-restricted and specialised plants and animals.

McDougall, A., Milner, R. N., Driscoll, D. A., & Smith, A. L. (2016) Restoration rocks: integrating abiotic and biotic habitat restoration to conserve threatened species and reduce fire fuel load. Biodiversity and Conservation, 25(8), 1529-1542.

To examine the influence of rock habitat and native grass restoration and management scenarios (fire and herbicide application) on the use of the threatened Pink-tailed Worm Lizard (Aprasia parapulchella).

Rock restoration combined with herbicide application reduced fire fuel load, increased ant occurrence (the primary prey of A. parapulchella) and increased the growth and survival of native grasses. Threatened lizards colonised the restored habitat within a year of treatment.

Michael, D. & Lindenmayer, D. (2018) Rocky Outcrops in Australia: Ecology, Conservation and Management. CSIRO Publishing, Collingwood, Australia.

To increase awareness of the biological, cultural and social values of rocky outcrops, the flora and fauna that depend on these systems and to provide management recommendations to improve their conservation values.

Rocky outcrops in Australia have a diverse range of ecological, cultural and social values. Many outcrops in commodity production landscapes are highly degraded and require urgent management.

Michael, D. R., Cunningham, R. B., & Lindenmayer, D. B. (2008) A forgotten habitat? Granite inselbergs conserve reptile diversity in fragmented agricultural landscapes. Journal of Applied Ecology, 45(6), 1742-1752.

To examine the relationships of reptile diversity, rocky outcrop patch size and habitat condition.

Small insular rock outcrops in agricultural landscapes are important for supporting farm reptile communities and specialised rock-dwelling lizards. Large, structurally complex outcrop in variegated landscapes support highest levels of reptile diversity.

Michael, D. R., Lindenmayer, D. B., & Cunningham, R. B. (2010) Managing rock outcrops to improve biodiversity conservation in Australian agricultural landscapes. Ecological Management & Restoration, 11(1), 43-50.

A review of the literature on granite outcrops in agricultural landscapes.

Rocky outcrops are prominent in agricultural landscapes. Reptiles are a major component of these habitats and many species are restricted to, and more abundant on, rocky outcrops. Rock outcrops provide reptiles with resources that are limited in the surrounding landscape (e.g. micro-gradients in climatic conditions, basking and retreat-sites). Significant knowledge gaps exist on the conservation values of small, rocky outcrops.

Pike, D. A., Croak, B. M., Webb, J. K., & Shine, R. (2010) Subtle–but easily reversible–anthropogenic disturbance seriously degrades habitat quality for rock‐dwelling reptiles. Animal Conservation, 13(4), 411-418.

To investigated the effects of human-induced rock disturbance on saxicolous reptiles.

Crevices beneath displaced rocks were larger and cooler than those beneath repositioned rocks. Repositioning of rocks enhanced usage by reptiles. Both crevice size and temperature influence reptile retreat-site selection. Minor displacement of overlying rocks reduces habitat quality by modifying critical crevice attributes.

Shine, R., Webb, J. K., Fitzgerald, M., & Sumner, J. (1998) The impact of bush-rock removal on an endangered snake species, Hoplocephalus bungaroides (Serpentes: Elapidae). Wildlife Research, 25(3), 285-295.

To examine the impact of rock removal on an endangered snake species (Hoplocephalus bungaroides).

Snakes and the geckos prefer rocks lying on other rocks, rather than on soil, and select rocks of particular sizes. Rocks removed by bush-rock collectors overlap considerably in size (diameter and thickness) and position (rock on rock) with those used by broad-headed snakes and velvet geckos. Rock numbers were substantially reduced by anthropogenic disturbance. Bush-rock removal has contributed to the endangerment of a threatened snake.

Wong, D. T. (2013). Environmental factors affecting the occurrence and abundance of the Pink-tailed Worm-lizard (Aprasia parapulchella) in the Australian Capital Territory (Doctoral dissertation, University of Canberra).

To investigate the factors driving theoccurrence and abundance of the threatened Pink-tailed Worm Lizard (Aprasia parapulchella) in the ACT at regional and patch scales.

Loss and degradation of the ground layer habitat of Aprasia parapulchella, as a result of agricultural modification, has historically been the major driver of decline of the species across its range.