Overview of state and trends of the marine environment
What has changed since 2011?
- A marine heatwave generated by the 2011 La Niña event, superimposed on overall increasing water temperatures, caused widespread impacts on the marine environment off the Western Australian coast, including coral bleaching, fish and invertebrate deaths, and changes to species distribution and community structure.
- Apart from human-caused pressures, the Great Barrier Reef has been significantly affected by 2 events in the past 5 years. Cyclone Yasi in 2011 caused widespread direct damage to the reef, and the 2015–16 El Niño event, superimposed on overall increasing water temperatures, generated the highest sea surface temperatures across the Reef on record, resulting in extensive coral bleaching and die-off, particularly across the northern regions.
- Since 2011, 2 sea snakes, 2 seabirds, 2 sharks, 1 sawfish and 1 fish have been listed under the EPBC Act, and 2 fish species have been reclassified as critically endangered. Giant kelp forests across south-eastern Australia were the first marine community to be listed as a threatened ecological community, in 2012.
- Australian populations of humpback whales (Megaptera novaeangliae) have increased to the point that their current listing as vulnerable could now be reconsidered (Bejder et al. 2016).
- Since 2010, 34 new Commonwealth marine protected areas have been declared, resulting in a total of 323 million hectares.
State and trends
Australia’s marine environment encompasses the seabed; the water column; physical, biogeochemical and ecological processes that play an important role in shaping the marine environment; and habitats, communities and species groups, which all interact in highly complex ways.
Marine habitats and communities
Generally, habitats and communities in the Temperate East Marine Region and the South-east Marine Regions have been subject to higher historical impacts, such as bottom-trawling impacts on shelf and slope communities, than those in other regions (Pitcher et al. 2015, 2016). Decreasing fishing effort during the past decade has reduced the trawling footprint, which has reduced the impacts on these communities. Fishery closures and marine reserves also offer additional protection for seabed communities.
The condition of habitats and communities in the Great Barrier Reef to the end of 2015 is considered to range from poor and deteriorating (corals) to good and stable (macroalgae, offshore banks and shoals). Recent surveys of the Great Barrier Reef have reported both increases and decreases in coral cover, with trends highly variable across monitored sites.
Extensive surveys of the Great Barrier Reef and the reefs of the north-west during the first half of 2016 recorded widespread and extensive bleaching of coral reefs, particularly in the north, as a result of climate extremes and record high water temperatures. In Western Australia, large areas of bleaching occurred at Scott and Seringapatam reefs, and parts of the inshore Kimberley coast, but little or no bleaching was observed in more southerly areas such as Ningaloo Reef and the Montebello Islands.
Large canopy-forming seaweeds are still prevalent in many locations around Australia, although there are documented examples of habitat loss off the coast of Western Australia from the south-east Indian Ocean marine heatwave (e.g. Wernberg et al. 2012). Increased water temperatures and range extension by the sea urchin Centrostephanus rodgersii in south-eastern Australia have led to the loss and overgrazing of kelp beds in temperate rocky reefs (Ling et al. 2015).
Most marine species groups assessed for SoE 2016 are regarded as being in good condition overall, although information is lacking to assess the condition or trend of many species and species groups because they are not monitored regularly, if at all.
Some species have improved from historical declines, including populations of humpback whales. Some species have declined because of cumulative impacts associated with pressures occurring across their marine, and nesting and breeding habitats. These species include flesh-footed shearwater (Puffinus carneipes) (Lavers 2015), Australian sea lion (Neophoca cinerea) (Goldsworthy et al. 2015), north Queensland hawksbill turtle (Eretmochelys imbricata) (GBRMPA 2014a) and some demersal shark species (Georgeson et al. 2015).
Several species with wide distributions that extend beyond Australia’s exclusive economic zone (e.g. marine turtles, seabirds, pelagic fish species) are being affected by high fishing effort or high bycatch rates in areas outside the Australian marine environment.
Trends are stable or improving for most fish species, except inner-shelf reef species, which are highly variable, with some populations in good condition and stable, and others in poor condition and deteriorating. Population trends for mobile invertebrates found on rocky reefs have been relatively stable on average. Fisheries management measures have stopped the overfishing of some species groups, although, for some species, such as eastern gemfish (Rexea solandri), blue warehou (Seriolella brama) and redfish (Centroberyx affinis), signs of recovery have not yet been seen. The reasons for this are currently unclear (Georgeson et al. 2015), but changing environmental conditions associated with climate change might be partly responsible.
Marine biophysical and ecological processes
Overall, biophysical and ecological indicators of marine health show the marine environment to be in good condition, although a number of indicators are highly variable in space and time, and so determining trends is difficult.
On a national scale, water column turbidity (cloudiness) in open-water environments has decreased, largely because of improved wastewater treatment, reduced nutrient inputs, and improved management of agricultural practices and associated run-off.
Reductions in primary productivity (the rate at which new organic matter is developed at the base of the food web) and secondary productivity (the rate at which this new organic matter is transformed throughout the food web) have been observed. These reductions are considered to be associated with reduced nutrient supply because of ocean warming.
Changes to ocean currents associated with climate change have affected connectivity within marine ecosystems, as observed through shifts in species distributions, especially in south-eastern Australia. The food webs of some ecosystems have changed as a result of commercial and recreational fishing, pollution, introduction of foreign species and habitat modification. Some of these impacts are irreversible, but the effects are generally unknown. The numbers of introduced species, jellyfish and algal blooms, and infestations and diseases appear to be stable, while trends in outbreaks of the crown-of-thorns starfish are unclear.
The National Representative System of Marine Protected Areas is developing steadily, with 40 Commonwealth marine reserves added since 2011 to those already proclaimed in the South-east Marine Region. Management plans for the marine reserves in the South-east Marine Region have been implemented. Those developed for the remaining reserves have been recently reviewed and are currently under reconsideration by the Australian Government. Marine parks and reserves now cover approximately 40 per cent of the Commonwealth marine area, and between 5 and 50 per cent of the area of state and territory waters.
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 the marine environment. In: Australia state of the environment 2016, Australian Government Department of the Environment and Energy, Canberra, https://soe.environment.gov.au/theme/overview/marine-environment/topic/overview-state-and-trends-marine-environment, DOI 10.4226/94/58b65510c633b