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Coastal Zone Wetlands

Coastal zone wetlands include mangrove and estuarine (areas of coastal river mouth characterised by tidal effects and mixing of fresh with sea water) ecosystems.

 

Millennium Ecosystem Assessment Reporting Category

Coastal Ecosystems

 

What ecosystem functions do coastal zone wetlands perform?

Sediment is trapped by the roots of vegetation which allows new vegetation to colonise.

Coastal zone wetlands provide important foraging, breeding and nursery habitats especially for marine animals and birds.

Coastal zone wetlands are located at the interface between terrestrial (land) and marine ecosystems. This position enables coastal zone wetlands in SEQ to perform highly (relative to other ecosystems) many ecosystem functions important to the provision of ecosystem services (see Table 1). By nature of their location, at one end of the spectrum they regulate disturbance by flood waters derived from adjacent catchments; at the other end of the spectrum they buffer against erosion from tidal regimes and storm surges. Wetlands slow the velocity of flood water, absorbing it and slowly releasing it into the marine receiving waterways. Whilst performing this function, sediment is being trapped by the roots of vegetation and at the same time nutrients are being absorb and converted into plant biomass. This biomass then becomes available as food for herbaceous animals, which inturn become food for other animals higher up the food chain.

Bacteria play one of the most important roles in coastal zone wetlands. Using nitogen (N) as an example, inorganic nitrogen (nitrogen compounds that do not contain carbon) in the form of ammonia (NH3) adheres to sediment particles transported by flood waters. Aerobic bacteria (bacteria which require oxygen in order to grow and survive) then react with the ammonia. Further aerobic reactions occur (reactions that require oxygen to happen) to turn this ammonia into nitrite (NH4NO3) and eventually organic nitrogen (nitrogen compounds that contain carbon). As very few organisms have the ability to use nitrogen in inorganic form, this makes nitrogen bioavailable for plant uptake. Organic nitrogen trapped in soils in anoxic environments (environments with no oxygen) have anaerobic bacteria reacting with the organic nitrogen releasing the organic nitrogen into the atmosphere.

A common function of all vegetation and especially from wetland species is the regulation of climate. Vegetation regulates atmospheric processes through the absorption of carbon dioxide (CO2) and the release of oxygen (O2) and regulating temperatures through the provision of shade. Gas exchange processes in coastal wetlands however, also apply at the microscopic level in terms of microscopic algae being present in the waterways. Oxygen produced by microscopic algae not only supply oxygen to the wetland waterway itself, but also provide a food source for juvenile fish and prawns.

As sediment is trapped and collected through catchment and marine processes, coastal land is naturally formed and built on the coastal fringe providing areas for more mangrove and saltmarsh plants to colonise. This new vegetation creates more supporting habitats for marine aquatic animals such as fish, crustaceans and molluscs. Coastal wetlands provide nursery areas for at least 75% of all marine animals during their life cycle. This habitat also shelters migratory and resident birds, especially birds requiring tidal roosts. Fruits and seeds from wetland vegetation are often found in the flotsam on beaches and riverbanks and thus open water pelagic and beach ecosystems are important to the replenishing of coastal zone wetlands.

 

Table 1:The relative magnitude (to other Ecosystem Reporting Categories) coastal zone wetlands perform each ecosystem function.

Ecosystem Function Category Ecosystem Function 0
1
2
3
4
5
Regulating Functions
Gas Regulation            
Climate Regulation            
Disturbance Regulation            
Water Regulation            
Soil Retention            
Nutrient Regulation            
Waste Treatment and Assimilation            
Pollination            
Biological Control            
Barrier Effect of Vegetation            
Supporting Functions
Supporting Habitats            
Soil Formation            
Provisioning Functions
Food            
Raw Materials            
Water Supply            
Genetic Resources            
Provision of Shade and Shelter            
Pharmacological Resources            
Cultural Functions
Landscape Opportunity            

 

What types of coastal zone wetlands are in SEQ?

Different wetland species prefer different mixes of fresh and salt water, as well different levels of inundation. Coastal zone wetlands include saltpans with vegetation comprising Sporobolus virginicus grassland and samphire herbland. Other vegetation communities include swamps, woodland, open forest to low closed forest with dominant species Melaleuca quinquenervia or M. viridflora, Casuarina glauca, Corymbia spp., Eucalyptus spp., Acacia spp., Baumea spp. and Juncus spp.. This Ecosystem Reporting Category contains the following Regional Ecosystems: 12.1.1, 12.1.2, 12.1.3, 12.2.5 (a), 12.2.7 (a, b, c, d), 12.2.11, 12.2.12 (a, b), 12.2.15 (a, b, c, d, e). 

 

What is the area and extent of coastal zone wetlands in SEQ?

Coastal Zone Wetlands cover approximately 562 km2, 2.24% of SEQ. This maps shows coastal wetlands occuring in land zones of estuarine and on old coastal sand deposits such as in Cooloola and Noosa areas (e.g. The Everglades), lower Maroochy River, Pumicestone and Bribie Island and Moreton Bay and other Bay islands. A few scattered coastal wetlands also exist in the southern parts of the Gold Coast. A significant coastal wetland area exists on North Stradbroke Island known as 18 Mile Swamp. Boondall wetlands is one of the biggest wetland systems within the Brisbane Metropolitan area.

 

Wetland species vary in their preference for fresh and salt waters and levels of inundation.

In SEQ, the majority of residents live on the coast.

Access paths allow people to learn and interact with wetlands.

Links to other publications and websites

Queensland Coastal Plan
WetlandInfo
Australian Wetland Information
Ramsar Convention

 

What is the vulnerability of coastal zone wetlands and threats to this ecosystem in SEQ?

Coastal zone wetlands are most vulnerable to human development pressures and associated population growth. In Queensland, loss of wetlands has been ascertained to: land-use decisions made without coordinated planning and management of wetlands; inadequate buffers between wetlands and surrounding lands; and changes to wetland drainage and water flow. In the SEQ region the majority of residents live in the coastal areas. Land is becoming increasingly scarce in these areas and coastal wetlands are often filled in for housing developments. Some coastal zone wetlands have been dredged for sand. Dykes, ponded pastures and constructed barrages in coastal areas have affected the flow of saltwater into the wetlands, upsetting the natural balance.

Flood control and water conservation works can affect wetlands also. Some wetlands have been inundated to form water storages, while others have been damaged by works to prevent flooding and ‘improve’ drainage. Fringing wetland plants have commonly been removed and as agricultural areas have expanded, wildfires have damaged some ephemeral wetlands, particularly where introduced drainage measures have led to the wetland drying out. Introduced livestock and feral pigs grazing around wetland edges can damage fragile wetland plants and cause sedimentation. Introduced plants have choked some wetlands and introduced fish have preyed on or outcompeted for food against native wetland species.

Comparative to many other ecosystems in SEQ, coastal zone wetlands are relatively resilient to short term shocks. This is a requirement for species inhabiting the harsh conditions at the interface of terrestrial and marine processes. Natural threats to coastal zone wetlands also exist however. These can include cyclones, strong winds and storm surges. Areas where only a small amount of coastal wetlands remain are less resilient than larger areas, so damage is often exasperated in these areas. Longer term pressures imposed on wetland systems decrease the potential of wetland systems to function and therefore recover.

 

How do we manage coastal zone wetlands in SEQ?

Coastal zone wetlands are managed both at the local government and state government level.  Some coastal wetlands have management plans that help provide actions and activities that should occur to that particular wetland (e.g. Boondall Wetlands and Tinchi Tamba Wetlands in Brisbane).  However there are many other coastal wetlands that don't have such plans (e.g. Hays Inlet in the Moreton Bay Regional Council region). In this case, the Queensland Coastal Plan (managed by the Department of Environment and Heritage Protection) provides protection. The Department of Environment and Heritage Protection also manages the Wetland Info website providing a resource for those wishing to understand the implications of managing coastal zone wetlands in SEQ.

A good example of wetland management is Boondall Wetlands. Boondall Wetlands has a Management Plan, managed access paths and bike way and a Environmental Education Centre that raises awareness of coastal wetland ecology and the value of wetlands. It has a funding source that comes from a Bushland Levy paid by Rate Payers that helps fund and support the wetlands maintenance and activities.

In SEQ there are a number of non-government community groups that volunteer their time to work in coastal wetlands. In most cases they are affiliated or join local council’s coastal Bushcare or Coastcare programs. There are other groups however that are dedicated wetland organisations such as ‘Friend of the Russel Island Wetlands’ or ‘Boondall to Tinchi Tamba Wildlife Preservation Society’. These organisations often gain funding support from their local council or gain Grants from the Australian and State Governments to do on-ground activities to enhance and protect the wetlands (e.g. protective fencing and interpretive signage).