Rocky outcrops are ‘island-like’ natural exposures of bedrock that are found in many different farming landscapes. Large rocky outcrops, especially exposures of granite but also sandstone, limestone and basalt are important for conserving the specialised plants and animals that use this habitat, harnessing water, contributing to soil nutrients and providing livestock with shelter from the wind and sun.
With appropriate management these habitats can become important assets for biodiversity conservation and can lead to improved productivity and profitability outcomes.
Well-managed rocky outcrops support a diverse number of native plants and wildlife that boost farm biodiversity and contribute to the provision of ecosystem services, such as crop pollination, and water and soil nutrient cycling.
Rocky outcrops are generally found in upper catchment areas and are important for harnessing ground water and surface runoff. They are also highly susceptible to erosion, weed colonisation and inappropriate fire regimes.
To maximise infiltration of water into the soil, slow and filter runoff, and minimise erosion, rocky outcrops should have good vegetation cover including a shrub layer, perennial grasses and moss cover. The benefits of improved water absorption into the soil extend into adjoining paddocks and across the property via natural spring and soaks.
By strategically allowing occasional stock access to well-managed rocky outcrops they can be important assets during lambing or after shearing because of the shelter they provide. Even when stock are excluded, the shelter provided on the periphery of a well-managed fenced off rocky outcrop is also advantageous to livestock.
Well-managed rocky areas also provide necessary habitat for species that provide important environmental services, such as crop pollination (native bees) and pest management (e.g. carpet pythons, which are predators of agricultural pests).
Rocky outcrops rise above the surrounding landscape, influencing weather patterns and creating a broad range of microclimates. Moist sheltered areas provide specialised plants and animals with vital habitat features (e.g. overhangs, caves, cracks and crevices), shelter from predators and weather – providing important refuges in often heavily cleared landscapes. The shallow soils and sun-exposed rock surfaces support highly specialised vegetation communities, and the architecture of the rocks themselves create conditions that are used by a diverse range of specialised rock-dwelling fauna. Because of the different microhabitats, rocky outcrops often support high levels of biodiversity relative to their size. Due to their isolation, rocky outcrops support species that are endemic, have adapted to local conditions, and are rare or vulnerable to extinction.
Rocky outcrops provide stepping stone habitats across the landscape facilitating the movement of migratory bird species and other wide ranging fauna. Many species are reliant on rocky outcrops for breeding, including various species of rock-wallaby, cliff-nesting birds such as the Peregrine Falcon, and hill-topping butterflies.
In highly modified landscapes such as farms, the durability and ruggedness of these rocky islands often results in them being the last remaining refuge for many species. They may look resilient, however, rocky outcrops are fragile ecosystems that are easily degraded by inappropriate human activities.
Over 200 native animals are restricted to rocky outcrops and more than 50 of these, such as the Pink-tailed Worm-lizard, Brush-tailed Rock-wallaby and Southern Bent-wing Bat, are threatened with extinction. Similarly, a large number of plants and vegetation communities associated with rocky outcrops are threatened, such as the Narrabarba Wattle, Bega Wattle and Woolly Ragwort. It is estimated that 170 plant species associated with rocky outcrops in NSW are threatened with extinction.
With appropriate management rocky outcrops can deliver a number of benefits for farm productivity and can become biodiversity hotspots.
|Productivity and profitability benefits||Biodiversity benefits|
There are a number of actions you can take to enhance rocky outcrops to improve the productivity, profitability and biodiversity of your farm.
1. Control or exclude livestock
Controlling or excluding livestock grazing is the most effective method for protecting and preserving rocky outcrops.
Livestock damage rocky outcrops in various ways, these include overgrazing the ground vegetation, changing the composition of the plant community, causing the loss of sensitive plant species, supressing the regeneration of trees and shrubs, destroying shrubs and other midstorey plants, physically trampling surface rock and burrows in the soft soils, and accumulation of excess nutrients on the site.
The impact of livestock will vary with type, the stocking rate, time stock were left in and excluded and the timing of grazing. How livestock are managed in these areas will largely depend on the desired outcomes, for example if you wish to manage the site for the conservation of sensitive native plant species, livestock exclusion or very strict periodic grazing would have to be implemented depending on the vegetation type and structure.
2. Carefully monitor and control pest animals
Rocky outcrops can also provide habitat for pests such as rabbits, goats, deer and foxes. These species can have negative impacts on production and the environment. Consideration should be given to the impact of non-target species (such as pythons and quolls) when implementing pest control measures such as applying poison baits and burrow ripping.
3. Revegetating with trees and shrubs
Many rocky outcrops are heavily disturbed and largely cleared. Such outcrops will benefit from careful revegetation of native trees and shrubs, enhancing the feature for biodiversity and production.
However, if planting trees near your outcrops, take caution – dense plantings, particularly of eucalypts, can crowd out desired shrubs and wild flowers, and reduce reptile populations.
4. Leave surface rock and logs
Surface rocks are an important habitat around rocky outcrops for many species, such as Pink-tailed Worm-lizards. It is common practice to collect these rocks for gardens or in an attempt to improve access for farm machinery. These practices have negative impacts on biodiversity. Similarly, logs also contribute to the environmental values of an area. Where these have been removed, the addition of rocks and logs can have positive outcomes.
5. Protect outcrops from overabundant native herbivores
Improved environmental management and increases in woody vegetation around rocky outcrops benefit other species, such as kangaroos, wallabies and wombats, which all have important roles in the natural ecosystem. To ensure these species and your rocky outcrops coexist, installing kangaroo-proof fencing may be necessary to protect your outcrop.
6. Create a native plant conservation area
Rocky outcrops support high native plant diversity. The variation in shade, shelter and moisture levels of the soils allow for this. While some rare and threatened plants still exist on some outcrops, enhanced rocky outcrops also provide an opportunity to re-establish some of those plant species. This will benefit native bees, birds and butterflies, and can create reservoirs and seed banks for rare and/or threatened species.
- Avoid planting trees in positions where they continuously shade rocky structures.
- Link enhanced rocky outcrop areas with other habitats such as creek lines or other outcrops with fenced off shelterbelts/corridor plantings.
- Don’t plant trees too densely, as this can shade out shrub and midstorey layers.
- If grazed, minimise the time stock have access and allow a long enough recovery time (ideally a year) for plants to recover, especially the shrub layer and grazing sensitive plants.