Overview of state and trends of coasts
What has changed since 2011?
- Increasing human activity on the coast means that overall pressure is growing. Direct impacts have been caused by urban and agricultural developments, which are predominantly on the east, south-east and south-west coasts of Australia.
- The condition of some coastal species (e.g. saltwater crocodiles) and communities is stable or improving, but the majority are deteriorating. Of great concern is the continued decline in migratory shorebird populations and saltmarshes.
- Resource extraction and associated coastal infrastructure have increased in recent years, causing severe but localised habitat loss and degradation.
- In addition to ongoing pressure from metal and nutrient pollution, coastal waterways are threatened by new classes of pollutants. These include microplastics and nanoparticles, which are largely unregulated and whose effects are poorly understood.
- The past 5 years have seen many extreme weather events, including severe heatwaves, floods and storms. These have caused significant impacts on coastal structures, communities, habitats and species, particularly in Queensland.
State and trends
The condition of Australia’s coastal environment is mixed, being largely good in the north-west and far north-east of the country, and largely poor in the east, south-east and south-west. In the future, parts of the tropical north coast may be threatened by planned development, if this is not well managed. Resource extraction and associated infrastructure have grown in the past few years with the mining boom, causing severe but highly localised habitat loss and degradation. Shipping associated with resource extraction and trade has been linked to the introduction of non-native species in coastal areas.
Australia is beginning to experience the impact of climate change pressures on our coasts. Since 2011, climate change has manifested as increased frequencies of heatwaves and severe storms. Cyclone Yasi in 2011 caused extensive damage to the Queensland coast, affecting seagrasses (Rasheed et al. 2014) and, consequently, dugongs (Sobtzick et al. 2012). It also caused widespread damage to the Great Barrier Reef (GBRMPA 2014). In the same year, flooding in Brisbane caused damage worth an estimated $440 million (BCC 2012). In 2016, climate-related stress resulted in the loss of approximately 10 per cent of Australia’s mangroves in the north. Increased frequency of extreme weather events, together with sea level rise and the associated erosion and recession of the coast, will add stress to systems already stressed by other human activities.
Marine debris (human litter) is increasingly entering coastal waterways and marine environments, where it persists and accumulates. A recent nationwide survey found that approximately three-quarters of the debris found along the Australian coast was plastic (Hardesty et al. 2014). Debris can entangle animals, or be ingested and accumulate in shorebirds (Verlis et al. 2013), turtles (Koelmans 2015) and invertebrates (Canesi & Corsi 2016).
Of emerging concern are microplastics, which are small particles that are micrometres in size (Browne et al. 2015). These enter coastal waters through sewage contaminated by fibres from washing of clothes or from cleaning products; they can also occur from the fragmentation of larger plastics. The ecological effects of microplastics are largely unknown (Vegter et al. 2014), but they include blockage of digestive tracts and the transfer of organic toxins through food webs (Browne et al. 2013, Rochman et al. 2013).
Coastal habitats and communities
The state of many biological components of the coast is poor and deteriorating. Vital ecological processes are compromised near areas of human activity, because of multiple pressures on coastal ecosystems.
Sizeable stretches of Australia’s coastline have been altered from their natural state by development, invasive species and recreational use. Approximately 10 per cent of the shoreline within the Great Barrier Reef World Heritage Area now comprises human-made structures (e.g. breakwalls, pontoons, jetties)—an increase of 70 per cent in some areas in the past 3 years (Waltham & Sheaves 2015). Native coastal vegetation has been lost to clearing, soil quality has diminished, and island flora and fauna are being severely affected by invasive species.
Many of the ecological services and processes that natural ecological communities deliver and depend on are being disrupted by human-driven deterioration of the coast. For example, widespread increases in organic enrichment of coastal waterways have substantially altered the processes of nutrient cycling, sulfur metabolism and carbon fixation. Several estuaries and bays around the nation are centres of urban, industrial and agricultural activity, and are demonstrating reduced water and sediment quality (Dafforn et al. 2012), and altered fish and invertebrate communities (Clark et al. 2015).
Many EPBC Act–listed nationally threatened species occur on the coast.
The destruction of critical nursing, roosting and nesting sites globally and regionally has had broad-reaching ramifications for species that rely on networks of sites to maintain populations. In particular, migratory shorebirds are declining as a result of habitat loss and impacts on critical parts of their migratory route in other nations (Clemens et al. 2016). This is occurring despite protection in Australia, and looks as though it will continue.
Critical habitat-forming species groups, such as saltmarshes, seagrasses and shellfish, have not yet recovered from extensive historical losses, although restoration programs are currently under way. Saltmarshes, in particular, are in a poor and vulnerable state. Their current extent around urban centres is a fraction of their pre-European extent, and they are now subject to further clearing and drainage, and the encroachment of mangroves landwards. The continued decline of saltmarshes is a significant concern, partly because of their role in carbon sequestration.
Jackson WJ, Argent RM, Bax NJ, Bui E, Clark GF, Coleman S, Cresswell ID, Emmerson KM, Evans K, Hibberd MF, Johnston EL, Keywood MD, Klekociuk A, Mackay R, Metcalfe D, Murphy H, Rankin A, Smith DC, Wienecke B (2016). Overview: Overview of state and trends of coasts. In: Australia state of the environment 2016, Australian Government Department of the Environment and Energy, Canberra, https://soe.environment.gov.au/theme/overview/coasts/topic/overview-state-and-trends-coasts, DOI 10.4226/94/58b65510c633b