Saltmarshes have previously been viewed as dumping grounds with little value, often being reclaimed for coastal development. Although still very much under threat, these habitats are now recognised by coastal managers as significant areas that play a major role as nutrient sinks, provide habitats for a wide range of juvenile fish and bird species, and also act as a buffering and filtering system for sediments and nutrients.

Even in areas where saltmarshes have been preserved, impacts from adjacent development caused by stormwater outlets, vehicular traffic and vegetation dumping affect the function of saltmarsh communities. Alteration in salinity from stormwater can greatly affect community diversity in these areas, as well as cause erosion and sedimentation problems. Weed infestation due to stormwater or vegetation dumping alters the biodiversity of saltmarsh areas. Traffic within and grazing of these areas can change the drainage or microtopography, thus influencing the vegetation patterns and distribution. When damaged, it often takes saltmarshes many years to recover (Adam, 1995).

Saltmarshes are under threat not only from the impact of humans but by invasion from mangrove colonisation. Many cases of mangrove invasion into saltmarsh areas have been noted along the east coast of Australia. Where saltmarsh is restricted along its landward edge by development, it can be squeezed against these obstacles by landward-shifting mangroves (Saintilan and Williams, 1999). Some reported losses of saltmarsh include small areas of natural loss of marine couch at the upper tidal limits as a result of invasion by Casuarina glauca in south-east Queensland (Queensland Herbarium, 2001).

There may be a number of factors contributing to the landward incursion of mangroves, including changes in rainfall patterns, agricultural activities, sea level rise and urban activities resulting in increased sediment and nutrient inputs. However, further research is still required to answer this complex issue.

What protection exists?

All saltmarsh vegetation is protected under Queensland legislation through the fisheries Act 1994. This protection ensures that there are healthy fish habitats available for shelter, feeding and nursery areas for fish stocks. Additional protection of saltmarsh communities (and other marine plants such as mangroves and seagrasses, and non-vegetated tidal areas) occurs throughout Queensland within Fish Habitat Areas declared under the FisheriesAct 1994.

Contact DPI&F Call Centre on 13 25 23 for further information regarding required approvals for work or research proposals relating to saltmarshes, or visit our website at www.dpi.qld.gov.au

Saltmarsh weeds and associates

The species identified in this guide are the most common plant species found within Queensland saltmarshes. However, there are others, including introduced or weed species. Some introduced saltmarsh species have become naturalised, such as the greencouch (Cynodon dactylon) and jointed rush (Juncus articulatus) (Batianoff and Butler 2002).

Common weed species found within saltmarshes include the following: coast barbgrass (Parapl-iolis incurva); green fat-hen (Chenopodium murale); hottentot fig (Carpobrotus edulis); jointed rush (Juncus articulatus); and sand spurry (Spergularia rubra).

The value of these weed species in the saltmarsh is not clearly understood, but the main concern is their ability to compete with native species and reduce the biodiversity of the saltmarsh.

Some species are more commonly found in dunal habitats rather than in saltmarsh, but sometimes they may overlap these habitats. These species include: burrs (Sclerolaena spp); fleabanes (Conyza spp); grasses (lschaemum australe, lschaemum fragile and Lepturus repens); pigweed (Trianthema spp); prickly couch (Zoysia macrantha); and tropical beachgrass (Thuarea involuta).

Other adjacent species on the terrestrial side of saltmarsh, such as New Zealand sea spinach (Tetragonia tetragonoides), are often referred to as saltmarsh species.

Vegetation associated with saltmarsh areas grows on the periphery, or occasionally within the saltmarsh itself (associate species). Salt tolerant saltmarsh associates that grow in close proximity to saitmarshes include: mangrove fern (Acrostichum speciosum); paperbark and tea tree (Melaleuca spp); and she-oak and swamp oak (Casuarina spp).