In the Great Barrier Reef Region, there are multiple activities and changes affecting the health of sensitive and complex coastal ecosystems.
Many of the pressures facing coastal ecosystems and the Great Barrier Reef stem from past decision-making.
These include broadscale clearing, estuarine saltmarshes being converted into pasture land, the exposure of acid sulphate soils in estuarine areas, floodplain levelling for cropping, dams and water extraction, ports and coastal development, and infrastructure development along the coast.
A marked decline in inshore biodiversity has been one of the consequences of these changes.
These modifications have also affected water quality by reducing sediment and nutrient recycling, restricted the movement of many species between marine and freshwater environments, and encouraged the establishment of pest species which cope better with degraded conditions.
The legacy of these past practices mean we need to focus on halting the loss of coastal ecosystems and work to protect, repair, reconnect, restore and rehabilitate many of their ecological functions.
Changes in rainfall, storm frequency and intensity, increasing temperatures, rising sea levels, ocean acidification and other predictions associated with climate change represent significant additional pressures on coastal ecosystems.
Nearly three-quarters of the Great Barrier Reef catchment is used for grazing.
The capacity for modified coastal ecosystems to function well – such as through rainfall capture, groundwater recharge and nutrient cycling – are highly dependent on the way in which the land is managed.
Irrigated and non-irrigated farming
Irrigated and non-irrigated farming practices such as drainage and infilling have led to a significant loss of freshwater wetlands, as well as forested areas, in the lower coastal floodplain.
The way in which land is managed can have a big influence on the capacity of coastal ecosystems to continue providing ecological services that support the Reef.
Reef Plan is supporting farmers to adopt practices which support both the environment and their enterprises.
A lot of urban development has occurred within the coastal zone. This has been largely driven by land use, mining and industry, population growth, urban infrastructure and port development – all of which significantly affects the Great Barrier Reef.
The greatest threats associated with coastal development are clearing or modifying wetlands, mangroves and other coastal ecosystems. More than 50 per cent of Australia’s freshwater wetlands have been degraded, modified or lost since European settlement.
Urban run-off can also result in litter being washed into the ocean – this can be ingested by wildlife, such as marine turtles or seabirds, or cause entanglement.
Without adequate planning and careful environmental management, population growth could increase pollution and sediments, decrease water quality and change land and sea connections, resulting in the loss of long-term health and function of the Reef.
Modifications to coastal ecosystems
Extensive habitat areas that support the Great Barrier Reef have been modified or cleared. For example, the health of seagrass meadows, which are important feeding and breeding grounds for dugong and turtles, have moved from moderate to poor over the last decade in areas south of Port Douglas.
Even when there is no substantial clearing, land use changes can still alter the way in which coastal ecosystems function. Tidal barrages, for example, change saline wetlands into freshwater wetlands this can disrupt fish migration and encourage pest species to take hold.
Cumulative impacts can also take their toll on coastal ecosystems. For example, the use of bund walls (retaining walls), dams and introduced pasture grasses can all affect the health of local fish species and impede their migration.