Pressures affecting estuarine ecosystems

Queensland

Pressures on Queensland's waterways vary between different regions and are often linked to the types of land uses that occur in the catchment. Overall, sediment, nutrients and pesticides are the major catchment pressures that broadly impact Queensland estuaries, but these vary in their relative importance in different areas.

Healthy Land and Water South East Queensland report card

Historic and current land management practices have caused substantial erosion in South East Queensland's (SEQ) catchments. Erosion leads to sediment or mud entering estuaries which reduces water clarity and can smother seagrass and riparian and intertidal plants, affecting estuarine habitats.

Sediment from diffuse rural and urban sources, including construction, is the current primary threat affecting estuarine health. The amount of sediment entering waterways depends on the condition of catchments including the extent of riparian vegetation, agricultural and urban development practices and rainfall.

A key pressure contributing to lower grades in urban catchments is population growth leading to increased development and urbanisation contributing sediment to waterways.

Systems in SEQ are also impacted by nutrients from agricultural run-off or in sewage treatment effluent. A major program of sewage treatment plant upgrades and stream rehabilitation has significantly reduced this pressure over the past 15 to 20 years.

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Reef Water Quality report card

Estuarine wetlands in the Great Barrier Reef catchment are exposed to range of chronic and acute pressures such as excess nutrients and sediment, pesticides, loss of connectivity, changes in hydrology, coastal development, climate change and sea level rise.

The Reef Water Quality Report Card assesses changes to catchment indicators including estuarine wetlands. The loss of estuarine wetlands is mainly due to draining and bunding associated with the conversion of estuarine plains to freshwater wetlands. The highest historical losses of estuarine wetlands occurred in the Boyne and Shoalwater catchments in the Fitzroy region.

The Paddock to Reef Integrated Monitoring, Modelling and Reporting program (Paddock to Reef program) was reviewed and updated in 2018 to reflect the new targets set in the Reef 2050 Water Quality Improvement Plan 2017–2022. Due to the changed targets, some of the 2017–2018 results are not directly be comparable to previous years’ reporting.

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Fitzroy Basin report card

The Fitzroy Basin is home to several rare and threatened species, and internationally significant wetlands. It has the greatest diversity of native freshwater fish in Australia and supports commercial and recreational fisheries significant to Queensland.

The Fitzroy Partnership for River Health has identified a number of pressures affecting estuarine ecosystems:

diffuse source sediment and nutrient pollution associated with mining and coal seam gas extraction
agricultural and urban development activities
regulation of river flows.

Proposed increases in agricultural development, more mining operations and increasing coal seam gas extraction have the potential to further impact estuarine ecosystem health.

Low rainfall and poor grazing practices together can lead to low ground cover, which can lead to increased sediment run-off during subsequent rain.

Fitzroy Basin’s flow is regulated by 28 dams and numerous weirs. In-stream barriers, impoundments and water extractions that occur in freshwater parts of the Basin still affect estuarine ecosystem health by impeding the spawning migrations of fish and changing estuarine habitat conditions.

Barramundi is one of a number of fish species occurring in this region that needs to move between the ocean and freshwater habitats as part of their lifecycle.

Report card naming in the Queensland State of the Environment report refers to the year of report card release, which may differ from the year given in the report card title or the year data group shown on regional report card partnership websites. Only data for regional report cards released before June 30 2020 are included.

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Gladstone Harbour report card

Gladstone Harbour and its associated catchments are used for a range of activities — from agriculture, industrial and urban development to fishing, dredging and shipping. These activities exert pressure on the harbour’s ecosystems and species.

According to the Gladstone Healthy Harbour Partnership, Gladstone Harbour is influenced by a number of environmental, social, cultural and economic drivers:

climate variability
environmental flows from catchments
hydrological connectivity
tidal flushing
naturally high levels of certain minerals
human population change
political and economic drivers.

Specific examples of pressures identified by the Partnership that may change the ecosystem health condition of estuarine ecosystems within the harbour include:

episodic disturbances
urban, industrial and agricultural development (resulting in habitat loss and the mobilisation of sediment, nutrients and toxicants into waterways)
altered environmental flows
point source pollution
light pollution
boat strike
marine pests
harvesting of seafood.

Report card naming in the Queensland State of the Environment report refers to the year of report card release, which may differ from the year given in the report card title or the year data group shown on regional report card partnership websites. Only data for regional report cards released before June 30 2020 are included.

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Mackay–Whitsunday–Isaac report card

According to the Mackay–Whitsunday–Isaac Healthy Rivers to Reef Partnership, the high-level regional drivers of ecosystem health in the region’s waterways are:

climate (including climate change and variability)
population growth
economic growth.

The current pressures on estuarine ecosystem health in the Mackay–Whitsunday–Isaac region range from those occurring on an international level, to Reef-wide and localised regional pressures. They include:

urban, coastal, and industrial development (and resultant wetland, saltmarsh and riparian habitat loss)
cyclones and episodic events (including drought and flood events)
agricultural development
fishing and hunting (recreational, commercial, and traditional)
tourism and recreational use
litter
diffuse source pollution (agriculture and urban)
point source (urban and industrial)
changes to natural freshwater flow regimes
invasive species (flora and fauna).

Severe Tropical Cyclone Debbie heavily impacted the region in early 2017. Although this is likely to have led to severe bank erosion and removal of riparian vegetation in parts of some estuarine ecosystems, the full extent of the cyclone’s impact is not yet known.

Report card naming in the Queensland State of the Environment report refers to the year of report card release, which may differ from the year given in the report card title or the year data group shown on regional report card partnership websites. Only data for regional report cards released before June 30 2020 are included.

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Wet Tropics Waterways report card

Key drivers and pressures affecting estuarine ecosystems in the Wet Tropics Waterways region, as identified by the Wet Tropics Waterways Partnership are:

climate change and variability
population growth
economic growth
cyclones and episodic events (including drought and flood events)
agricultural activities and development
urban coastal and industrial development
fishing and hunting (recreational, commercial, and traditional)
tourism and recreational use
litter
water resource development and alteration of natural flow regimes.

The Wet Tropics is characterised by high value coastal assets.

About 35% of land in the region is within the Wet Tropics World Heritage Area which provides some protection to the integrity of catchment waterways, including the connected estuarine ecosystems). Agricultural and urban land uses still impact a large proportion of waterways.

In-stream barriers, impoundments and water extractions that occur in the freshwater catchment affect estuarine ecosystem health by impeding the spawning migrations of fish and changing estuarine habitat conditions.

Fishing activity is common in the estuarine zone and has a more direct effect on estuarine ecosystem health.

Land use development has reduced the extent of wetlands, floodplains and riparian and mangrove communities in the estuarine zone. These habitats provide a range of functions including improvement of water quality by reducing nutrients, pollutants and suspended solids.

Report card naming in the Queensland State of the Environment report refers to the year of report card release, which may differ from the year given in the report card title or the year data group shown on regional report card partnership websites. Only data for regional report cards released before June 30 2020 are included.

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Townsville Dry Tropics report card

Different pressures affect estuarine conditions between the Cleveland Bay coast/estuary and the Halifax Bay coast/estuary zones.

Townsville Dry Tropics Partnership for Health Waters identifies key pressures on the Cleveland Bay coast/estuary zone as:

modification/development of coastal zones (including the creation of seawalls, sand dredging and coastal erosion)
urban and industrial contaminants
wastewater discharge (nutrient and salinity aspects)
chemicals in personal care products and microplastics that cannot be removed by conventional wastewater treatment.

In the Halifax Bay coast/estuary zone, pressures identified include:

land clearing and urban development
agricultural practices and associated pollutant run-off
septic systems (leaching of nutrients into waterways via groundwater flows).

Major flooding affected the region in 2019. The full impact on estuarine ecosystems is not yet known. However, significant amounts of sediments, nutrients and litter were transported through and into estuarine ecosystems and habitat degradation and fish kills also occurred. A significant amount of aquatic weed, washed from freshwater reaches of the Ross River to adjoining estuarine reaches, has been removed to prevent further habitat degradation.

Report card naming in the Queensland State of the Environment report refers to the year of report card release, which may differ from the year given in the report card title or the year data group shown on regional report card partnership websites. Only data for regional report cards released before June 30 2020 are included.

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