Our terrestrial and marine natural heritage is susceptible to the general pressures arising from climate change outlined above, as well as some of the pressures that flow from population and economic growth. However, other pressures apply particularly to natural heritage.

Pressures on natural heritage
Pressures on natural heritage
Invasive species
Invasive species and organisms place major pressure on natural ecosystems and their natural heritage values. Pest plants, pest animals and pathogens present an increasing threat to biodiversity generally, and specifically to threatened species (see the Biodiversity and Land reports). Many species, such as cane toads, carp, mimosa, feral cats, rabbits and camels, are already well established. Others, such as myrtle rust, pose serious emerging threats. There has been substantial national government engagement with biosecurity through the Intergovernmental Agreement on Biosecurity, which came into effect in January 2012, and substantial funding allocations to combat pest species, in accordance with the Australian Government Agricultural Competitiveness White Paper, which places particular emphasis on supporting agriculture (Australian Government 2015d; see Box HER10).
Impacts of invasive species on the natural environment may also affect Indigenous and historic heritage. For example, invasive weeds such as buffel grass and gamba grass greatly increase fire intensity and elevate the risk of damage to art sites, as well as changing the structure and composition of natural ecosystems. The widespread presence of invasive weeds in western Arnhem Land also affects the ability of traditional custodians to use the landscape for food gathering and ceremony (see Box HER21).
Box HER10 Astrebla Downs—management response to invasive species
The cat eradication and bilby recovery program at Astrebla Downs is an inspirational example of an effective management response to invasive species.
Astrebla Downs National Park (Astrebla Downs) was declared in 1996 to protect Queensland’s most significant population of the endangered greater bilby (Macrotis lagotis). In 2011, the bilby population at Astrebla Downs was estimated to be 700.
High rainfall on the Mitchell grass plains from 2009 to 2011 resulted in a plague of native long-haired rats (Rattus villosissimus), which provided an abundant food source and resulted in a feral cat population boom. In April 2012, a sudden influx of feral cats was reported at Astrebla Downs. Analysis of feral cat diets found that they were almost 100 per cent long-haired rat.
Queensland Parks and Wildlife Service rangers immediately implemented actions to control the cats, with some support from the Sporting Shooters Association of Australia.
In March 2013, the rat populations crashed, and cats were driven to switch to alternative food sources. Cats were observed hunting bilbies in April and May 2013, and analysis of the cats’ diets found that bilbies were a significant food source.
The primary control method was shooting, augmented by 1080 baiting. Approximately 3000 feral cats were shot from May 2012 to late 2015 (with an additional number eradicated by baiting). These controls, along with the depletion of virtually all food sources, led to a significant decline in cat numbers by June 2013.
Regular spotlighting has continued at Astrebla Downs since 2012. There was an 18-month period when diggings and scratchings were the only evidence of bilbies, and there was great concern for the survival of the species. Since May 2014, bilby activity and the number of bilby sightings have increased. Preliminary results of an aerial survey conducted in September 2015 indicate that the bilby population on Astrebla Downs is now around 1000 animals.
Queensland Parks and Wildlife rangers monitor cat numbers approximately every 6 weeks from April to September every year, and continue to implement control methods and investigation of cats’ diets.
Source: Marty McLaughlin, Principal Ranger Central Region, Queensland Parks and Wildlife Service

Feral cat (4.6 kilograms) killed with bilby (2 kilograms), 15 May 2013

Bilby at a burrow entrance, Astrebla Downs, May 2014
Loss of habitat
Habitat loss and fragmentation remain a major threat to Australia’s flora and fauna, and are directly responsible for the extinction of Australian species (see the Biodiversity and Land reports). Australia currently has a growing list of almost 1800 plants and animals listed nationally as threatened (Australian Government 2015e). Two major drivers of habitat loss are land clearing and climate change. Although large-scale land clearing is primarily a legacy issue representing past human activity, it continues to destroy native habitat in a number of states, particularly Queensland (see the Land report). Habitat fragmentation reduces the opportunities for species to move to more favourable habitats as the impacts of climate change intensify. Climate change will continue to exert pressure, and will increase the severity and frequency of fires, some invasive species and other events, such as droughts, floods, coral bleaching and saltwater intrusion into coastal freshwater systems. Fire and extractive industries can also irreparably change and reduce habitat.
Changing use
Changing land and marine use places pressures on both natural and cultural heritage. Landscape-scale shifts, such as new mining or large plantations on previous farmland, and ever-increasing urban sprawl may increase impacts on reserves, adjacent natural ecosystems and connectivity; alter wildlife corridors; or increase risks for rare and endangered ecosystems. There may be physical impacts from resource extraction, such as run-off or subsidence, or indirect impacts, such as altered groundwater flows. Even within reserves, changes to allow new recreational uses can lead to unintended pressures and damage if they are not well planned and carefully managed. Pressure from changing use may be reduced by strategic planning and decision-making that is informed by thorough resource assessment.
Loss of ecological connectivity
Related to loss of habitat and land-use changes is the progressive loss of ecological connectivity across the Australian continent. The disconnect between areas of particular species’ habitats can cause systemic degradation of the whole, leading to loss of biodiversity and resilience. This includes species and ecological communities becoming threatened or extinct, either locally or more broadly. The pressure is broader than suggested by the species and ecosystems that are formally recognised as threatened. Australia’s Biodiversity Conservation Strategy 2010–30 (National Biodiversity Strategy Review Task Group 2010) and the National Wildlife Corridors Plan (DSEWPaC 2012) recognise the need to improve connectivity (see Box HER11). Although improved connectivity remains a priority for the Australian Government, connectivity objectives are now being pursued through initiatives that are implemented at regional and local scales, such as the 20 Million Trees Programme (Biodiversity Working Group 2016) (see also ‘Connectivity and revegetation’ in the Biodiversity report).
Box HER11 Great Eastern Ranges Initiative
The Great Eastern Ranges Initiative (GERI 2016) is a strategic response to the ongoing decline and mass extinction of native species in eastern Australia. It draws together industry, government and nongovernment organisations that are active in the conservation of our natural heritage, seeking to promote landscape-wide connectivity and high-priority biodiversity projects within the corridor.
The project aims to support biodiversity by strengthening the habitat value of a 3600 kilometre corridor of native vegetation between western Victoria and far north Queensland (Figure HER1), enabling native species to move, adapt to and survive the environmental challenges that threaten their long-term survival. This is to be achieved by:
- improving the connectivity, condition and resilience of landscapes and habitats, thus halting the further decline and loss of species
- increasing the number of people working together in locally organised and managed regional partnerships to improve the connectivity and resilience of landscapes
- improving transfer of knowledge, skills and practices through community engagement, involvement and education
- improving understanding of species, ecosystems and local landscapes in the context of the wider Great Eastern Ranges, and their requirements for long-term persistence.
Source: Mackey et al. 2010
Soil erosion
Natural heritage places are affected by a variety of erosion forms: streambank, beach, tracks, gully, wind, mass movement and sheet erosion. Despite soil conservation programs, current rates of soil erosion across much of Australia exceed soil formation rates (see the Land report). Mass movement and sheet erosion have far greater potential for habitat loss and adverse impacts on natural heritage values than other forms. Erosion is exacerbated by changing climate, especially desiccation and increased wind, but, if not well managed, can also arise from economic factors such as development, changing land use or increased tourism.