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.

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).

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).

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.