Native vegetation and habitat

Australia’s native vegetation and habitats have been severely affected since European colonisation. Almost 40 per cent of forest (Bradshaw 2012) and more than 90 per cent of grasslands have been lost or heavily degraded. Dunes, which support many plant species, have been transformed or decimated as a result of coastal development and weeds (see Beaches and dunes), and foreshores are increasingly modified for human use.

Most of the loss of native vegetation has occurred near the coast, in areas of urban and agricultural land use (Figure COA10). The south-eastern and south-western coastal regions are the worst affected, with less than 25 per cent of native vegetation remaining in many coastal subregions. In contrast, native vegetation on the north and north-west coasts are mostly intact.

The state and trend of major vegetation groups can be viewed by considering what percentage remains versus the previous total extent. Of most concern are vegetation groups that have both low percentage remaining and low total extent, as these are both rare and heavily degraded. The vegetation group with the lowest percentage remaining is the Mallee Open Woodlands and Sparse Mallee Shrublands, which is also small in spatial extent. The percentage remaining has been stable for most groups from 2010 to 2014 (Figure COA11), but 2 that have showed decline are Casuarina Forests and Woodlands, and inland aquatic (freshwater, salt lakes, lagoons) vegetation. Troublingly, the 3 above-mentioned groups are also relatively low in extent.

Remote-sensing techniques provide an effective method of surveying vegetation and habitat at a national scale. AusCover, the remote-sensing data facility of the Terrestrial Ecosystem Research Network (TERN), holds a rich repository of various nationwide remotely sensed vegetation data, including the recently released National Biomass Library. Another remote-sensing product that was recently launched is the Data Cube—a collection of Landsat images from the past 30 years that have been processed and curated by Geoscience Australia and CSIRO. These and other products can be used to conduct new analyses of historical change in Australia’s vegetation cover, such as investigating relationships between vegetation change and population growth.

See the Land and Biodiversity reports for more detail on trends in vegetation cover.

Soil quality

Soil is a critical resource for water, carbon, energy and nutrient cycling. It provides fundamental support for nearly all coastal land ecosystems, and is a complex ecosystem in itself. Soil quality is determined by a combination of physical, chemical and biological properties. There are several ways to measure soil quality; commonly used indicators include sheet erosion, wind erosion, gully erosion, pH (acidity), organic carbon concentration, structure, salinity and acid sulfate oxidation status (Chapman et al. 2011). Soil quality is important for the microbial communities responsible for nutrient cycling (see Microbial processes and nutrient cycling). The natural quality of Australian soils is generally low because they are deficient in phosphorus, a vital nutrient for vegetation.

The recently developed Soil and Landscape Grid of Australia now provides a nationally consistent soil and landscape database. Development of the grid began in 2011, led by the Terrestrial Ecosystem Research Network in collaboration with researchers from CSIRO; the University of Sydney; Geoscience Australia; and Australian, state and territory government agencies. It combines historical data with new data generated from sampling, laboratory sensing, modelling and remote sensing, and provides access to the best available information about Australian soils and landscapes. Data for at least 11 soil attributes and 8 landscape attributes are available at 90 metre × 90-metre resolution (approximately 2 billion pixels in total), and each pixel also contains estimates of uncertainty. The grid is being used for a wide range of applications, providing information to urban and regional planners, land managers, farming groups, scientists and engineers.

One of the major soil issues for the Australian coast is acid sulfate soils. These occur when soils containing iron sulfide minerals are disturbed and exposed to air, creating sulfuric acid that can leach into waterways and decrease pH (Fitzpatrick et al. 2010). Acid sulfate soils are a natural phenomenon, but are exacerbated by human disturbances such as drainage of floodplains and wetlands. Some efforts have been made to remediate areas affected by acid sulfate soils, such as in the East Trinity Reserve near Cairns, Queensland, and vegetation communities here are responding to large-scale mitigation works (Newton et al. 2014). Hazard maps are required to provide information on the spatial distribution of acid sulfate soils (e.g. Naylor 1995), although little new information has been collected during the past 5 years and at the field or farm level.

In coastal–estuarine landscapes that are inherently rich in sulfidic sediments and saline watertables, natural resource management data need to be collected to describe the heterogeneous nature of the soil, the underlying regolith and interactions with groundwater. This is because these areas are used for agriculture but, increasingly, also for urbanisation. Geophysical methods, such as electromagnetic induction, are being used to value-add to the limited soil data because they are a cost-effective way of mapping the areal distribution of soil salinity and soil acidity (Huang et al. 2014). Increasingly, they are also being used to generate electromagnetic conductivity images (EMCI) of the soil continuum in 2D (Goff et al. 2014). More detailed work using 3D and 4D EMCI, akin to magnetic resonance imaging (MRI) scanning in health care, has also been shown to be able to measure and map beach face salinity (Davies et al. 2015).

See the Land report for more detailed information on soil.

Islands

Australia has 8222 islands, and these represent a significant proportion of Australia’s coast. These islands have a combined coastline of approximately 24,000 kilometres, which equates to approximately 40 per cent of Australia’s coastline (depending on how the coast is measured) (Geoscience Australia n.d.). Australia also boasts the largest sand island in the world—Fraser Island.

Several islands are biodiversity hotspots, and many support endemic species not found on the mainland. Some are home to critical populations of threatened flora and fauna, such as the land lobster (Dryococelus australis), which exclusively occurs on Balls Pyramid—a striking volcanic stack in the Lord Howe Island Marine Park. Many islands contain turtle nesting beaches, and some are important breeding grounds for seabirds, including threatened species of albatross and giant petrel (see Nursing, roosting and nesting). These species have been the subject of recovery plans since 2001, the most recent being the National recovery plan for threatened albatrosses and giant petrels 2011–16.

Threats to Australian islands warrant unique consideration, distinct from the mainland coast. Many islands are relatively unmodified because of their isolation, but others suffer from high rates of tourism and/or support permanent human settlement. Lighthouses are a common form of development on islands and the maintenance of these can have ongoing impacts. Some larger and more developed islands support agricultural and timber industries. Historically, islands have been used by Indigenous communities and are of high cultural significance.

For islands exposed to human visitation or settlement, the biggest threat to native flora and fauna is often invasive species (Priddel & Wheeler 2014). Macquarie Island is a prime example, with a turbulent history of biological invasion by rodents, rabbits and cats (see Box COA2). However, islands are also the most likely candidates for successful pest-eradication programs and can become refuges for wildlife threatened on the mainland. In the future, a major concern for islands is sea level rise, particularly for low-elevation islands, which will be catastrophically affected by even minor increases in sea level.

Much of the shallow water surrounding tropical islands supports diverse coral communities, including the approximately 1050 islands of the Great Barrier Reef (GBRMPA 2014). Great Barrier Reef islands are vital nesting grounds for turtles and seabirds (Congdon 2008), but are threatened by cyclones, invasive species, marine debris, coastal development and climate change (GBRMPA 2014). One Australian island on the Great Barrier Reef (Bramble Cay) is the first location to record a mammal extinction caused by climate change (the Bramble Cay melomys—Melomys rubicola; Gynther et al. 2016; see the Biodiversity report), and the Christmas Island forest skink (Emoia nativitatis) became extinct in 2014 when the last captive individual died (see the Biodiversity report).