Factors influencing the Region’s values
6.4.2 Vulnerability of the ecosystem to coastal development
Changes in land use over the last two centuries have determined the extent and condition of remaining natural ecosystems in the catchment. Overall, approximately 60 per cent of pre-clear vegetation — classified as remnant vegetation — remains intact in the catchment (see Figure 3.12).10 However, the status of coastal ecosystems varies greatly across basins (see Section 3.5). Coastal development continues to modify coastal ecosystems (see Section 3.5) and their functions. This has flow-on implications for the Great Barrier Reef ecosystem and its outstanding universal value as a world heritage area. Clearing or modifying of coastal habitats (such as saltmarshes, freshwater wetlands, forested floodplains and estuaries) close to the Region has significant effects on the feeding and reproduction of many marine species, as well as diminishing dry season refuges.10 For example, where forested floodplains have been lost through changes in land use, the areas no longer provide nesting habitat or roosts for waterbirds and shady migratory pathways for aquatic species with connections to the Great Barrier Reef.10 Another example is the replacement of coastal grasslands with intensive agriculture or urban settlements, reducing breeding habitat for many bird and reptile species, including estuarine crocodiles.10,172,173 The volume and speed of freshwater inflow can also be increased through coastal development activities such as clearing vegetation, hardening surfaces and straightening channels.174 These effects are likely to be amplified as the climate changes. Coastal reclamation has local effects on the Region’s environment, for example removing coastal habitats, permanently destroying marine habitats (such as seagrass meadows), altering small-scale local currents, impeding natural drainage from the catchments, altering groundwater flows and diminishing local aesthetic values. If not properly managed, reclamation works can affect water quality in adjacent waters and potentially expose acid sulphate soils. Artificial barriers to riverine and estuarine flow, such as dams, weirs, barrages, gates, levees, ponded pastures and weeds are widespread in the catchment. They affect the natural hydrology of the catchment and those Great Barrier Reef species that move between freshwater habitats and the sea. Many marine and estuarine fish species use the freshwater systems for part of their life cycle175 and can be affected by changes in water flow and the presence of artificial barriers. Artificial barriers have disrupted sediment supply to some beaches. The mobilisation of large quantities of iron and aluminium and heavy metals in surface and groundwater following the exposure of potential acid sulphate soils can affect many species at a local scale, both immediately and through accumulation in food chains. Examples include mangroves, seagrass meadows, invertebrates and fishes. In addition, south of the Region, exposure of the soils has been linked to algal blooms such as the toxic Lyngbya species.176 The effects are often long term and difficult to reverse.177,178 The localised presence of artificial light, sometimes exacerbated by removal of beachfront vegetation and topography, affects some species. They can be attracted to or deterred from light or become disorientated, and foraging, reproduction, communication and other critical behaviours can be disrupted.179 Artificial lighting can disorient nesting female turtles and their hatchlings by reducing the dominance of natural lighting cues.180,181 Seabird fledglings have been found to be attracted to artificial light, causing them to land and stay in urban areas.182
Coastal habitat changes and reduced connectivity affect the Region.
Development of ports such as Townsville has involved reclamation of marine areas